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Vol. 1 -
2007
Empirical analysis of information input for mobile
human-computerinteraction (Vol. 1 – 2007)
Author: Thomas
Alexander, Dieter Leyk und Christopher Schlick
Keywords:
Mobile computing · Personal digital assistant (PDA) · input performance
· Fitts´law
Summary
Mobility and mobile
computing are topics of growing importance within today’s and future
working processes. In general, it has to be differentiated between
portable and mobile computing. Portable computing refers to stationary
work at different locations while mobile computing is defined by working
on the move. Both have different characteristics which have to be
considered when designing the human-computerinterface. This paper refers
to mobile computing while walking. Frequent applications of mobile
computing are entertainment, information input and retrieval,
communication, and orientation. Common devices for mobile computing are
notebooks, tablet- PCs, cellular phones, and personal digital assistants
(PDA). For practical weight reasons only the last two are applicable on
the move. In addition to simple keypad interaction of cellular phones,
touchscreens with special input pens are used as input devices when more
complex inputs are required. The according graphic user interface (GUI)
consists of a modified standard desktop GUI with windows, icons, menus,
and pointer (WIMP). The user interacts nearly exclusively by means of
point-and-click. Additionally, different text recognition modules or
virtual, miniaturized QWERT-keyboards are used for text input.
Characteristics of mobility or movement are usually not taken into
consideration for HCI design. Instead, concepts of stationary desktop
computers are simply adapted. Previous studies show that this leads to
shortcomings in performance. One reason for this is that interaction
while walking is obviously a dual task with walking as primary task.
Walking requires attention resources, which leads to degraded HCI-performance.
Previous studies have also shown that mobile use leads to a different
use, performance, and workload. Thus, mobile HCI should be studied
during actual movement. But especially with walking this is true for few
studies only. In this study it was hypothesized that the movement state
effects input performance. In order to quantify the effect, measures of
performance were taken at different walking speeds on a treadmill. Input
performance was determined by error rate and Fitts’ index of
performance. They were measured with a target designation task on a PDA
while walking on a treadmill (speed: 0, 2, 3.5, 5 km/h). Experienced
participants (n=18) were asked to hit targets of different sizes (2.4 mm
to 12.0 mm) with changing positions on the display. The according Fitt’s
index of difficulty (ID) was varied from 2.0 to 5.6 with steps of 0.2.
Results show significant effects of ID and walking speed on error rate
(p<0.01). The ubsequent pairwise analysis revealed only significant
differences between error rates for two groups: (ID<4) and (IDe“4).
Consequently, the statistical analysis was repeated for each of them.
For movements with ID<4, ID and walking speed explained similar
proportions of variance (o²ID=31.4%; o²v=34.8%). However, a subsequent
regression analysis showed that the values for error rate increased only
slightly from 0% to 3.6%. For more difficult movements (ID e“ 4), both
factors explain comparable proportions of variance (o²ID=46.6%;
o²v=39.6%). The final regression analysis showed a strong increase from
an average error rate of 2,8% (ID=4, standing) to 22,2% (ID=5.6, v=5
km/h). Thus, the effect is much stronger for these visually-controlled
movements. With regard to Fitts’ index of performance an ANOVA proved
significant effects of walking speed on this variable (o²=23.9%). The
index of performance decreased from 8.5 bit/s (0 km/h) to 5.8 bit/s (5
km/h). Notice, that the effect of ID is included in the index of
performance by definition. As a consequence, Fitts’ law was extended by
an additional, speed-dependent term. The regressional analysis revealed
a quantitative description of the relation between input time, ID, and
walking speed. This study shows that walking with different speeds on a
treadmill has an effect on input performance. Consequently, movement
status and speed have to be taken into consideration when designing HCI
for mobile computing. This is especially important for the design and
size of icons and menu items of a GUI metaphor. Moreover, an
error-tolerant behavior has to be implemented when critical input is
required. In this study it was also found that error rate increases
strongly even though precision was prioritized by the instruction. In
reality, error rate might be even higher because of a missing
prioritization and higher environmental disturbance. Consequently,
movements with IDe“4 should be avoided. However, it is also found out
that stopping is a possible way to enhance input performance. This meet
reality, because most mobile users take a break when high precision
input into the mobile computer is required.
Practical Relevance
The importance of
mobility and the resulting technical requirements for mobile computing
is rapidly growing. But present Human-Computer-Interfaces for these
mobile systems are often designed with regard to stationary desktop
systems only and do not consider the special context of a mobile usage.
Consequently, they cannot be used when the user is walking or moving.
For a sensible mobile use, reference values for estimating expected
input performance and precision are required.
Support possibilities of the product development: Which changes in the
result are caused by question-based thinking about own solutions? (Vol.
1 – 2007)
Author: Constance Winkelmann und Winfried
Hacker
Keywords: Design Problem Solving · Question Answering
Technique Reflection
Summary
Design-problem
solving is conceptualized as an iterative process of self-evaluation and
correction of errors (Ullman, Dietterich & Stauffer 1988).
Question-answering techniques evaluating (the) obtained own results may
improve the quality of solutions of design (Wetzstein 2004; Winkelmann
2005). However, the degree of improvements is significant, but small and
only about half of the participants improve their solutions at all.
Therefore, this study analyses whether the types of the question-induced
modifications of own results of design problem solving may hint on
explanations for these limited question-induced improvements. Three
groups of subjects (N = 116; laypersons, students of engineering design
and experienced engineering designers) were asked to design a
sophisticated version of a grill. The manual sketches were evaluated by
experts before and after the intervention by a generic system of
interrogative questions aiming at the semantic relationships (e.g.
causal, conditional, final). The three groups of participants achieved
significant mean improvements of solution quality with small to medium
effect size. 82% of the participants modified their solutions at all in
spite of a large window of opportunity. About 60% of all participants
carried out modifications but did not really improve the solutions. 40%
of the modifications in principle led to solution improvements; however,
half of the participants only added some more or less relevant aspects.
The other half consisted in equal parts of error corrections,
continuations of the design principle begun, and of applications of a
new principle („productive modifications“). Laypersons, students and
engineering designers do not differ significantly as to these results.
Comparing the group with improvements to the group showing none reveals
that corrections, continuations of a solution begun, and applications of
a new design principle occur three times more frequent in the former.
This may not be taken for granted, though, since the correction of one
error, for example, may produce another error. The results hint on
restrictions on the application of questionanswering techniques so far:
the participants neither had an opportunity to get access to additional
knowledge nor to discuss their solutions with experts. Thus, the
efficiency of the questions may be underestimated. Moreover, reflection
by question-answering should become a component of engineering
education.
Practical Relevance
The analysis of the
changes of design solutions due to question-based reconsidering of these
solution shows that especially „productive“ changes (error corrections,
enhancements of the solution, development of a new solution principle)
alone and in combination with additions lead to improvements of these
solutions. In principle, it might be practical to use the
question-answering technique as an aid for the discourse with other
specialists when deliberating on (interim) solutions. Beyond that, we
recommend to integrate this question system into the training of
advanced students as they particularly can profit from the released
error corrections.
Benefits of 3D process visualization on fault
detection in process plant operation (Vol. 1 – 2007)
Author: Birgit Vogel-Heuser,
Karin Schweizer, Antje van Burgeler, Yvonne Fuchs1 und Dorothea
Pantförder
Keywords: · 3D visualization · fault · diagnosis · HMI
· process plant operation · work-load
Summary
Nowadays process plant visualization and operation
take place without the operator’s physical presence at the technical
device (plant, machinery). As a consequence a lot of complex systems
must be visualized simultaneously on one or more monitor, maybe with
several windows to be selected out of a menu. The monitoring of those
processes with conventional 2D human-machine-interfaces requires high
affordance in terms of operator’s attention
and increases work load. In this article an approach is introduced which
aims at the reduction of work load and complexity and by that faults
using 3D visualization. The process to be observed is a distance control
of a continuous hydraulic press, i.e. a field of analogue sensors
arranged in a spatial setting. The approach is evaluated in a lab
experiment.
Hypotheses: In an experimental study with 75 male and female
participants (aged from 18 to 46) we investigated three hypotheses: (i)
3D visualizations as surface plots reduce the amount of faults and the
time to detect faults compared to 2D visualizations when monitoring a
continuous hydraulic press (ii) 3D visualizations as surface plots
increase the presence compared to 2D measured through a presence
questionnaire. (iii) There is a relation between the increased presence
and the reduction of faults and time to detect faults.
Results: To investigate these hypotheses we simulated several different
problems referring to common problems with a continuous hydraulic press
as inclination of the press and torsion of the press table in different
views and dimensionalities (Details are given in Fuchs 2005; van
Burgeler 2005). We analyzed the number of hits, the reaction time
latencies for detecting faults and the presence score measured by the
questionnaire and received the following results. In contrast to
hypothesis (i) participants operating with 2D visualizations have
reacted as fast as participants operating with 3D visualizations. There
is, however, a significant interaction with the test conditions/versions
which is due to the different versions of the 3D visualization. When the
problem develops and diminishes in front of the operator there is an
advantage in terms of reaction time and number of faults for those
participants compared to another 3D-group (the problem is far above and
approaches to the operator) and compared to the 2D visualization. Our
hypothesis is also confirmed by a second finding: for one special
problem (the most difficult of all problems) participants of both 3D
groups react faster than the participants of the 2D group.
This trend can also be stated when regarding the number of hits.
Participants operating with 2D visualizations have discovered more
faults than compared to the ascribed 3D-group when the problem was far
above and approached to the operator.
We could also confirm our second hypothesis. There is an increase of
presence in both 3D groups. We could, however, not confirm our third
hypothesis. We could not find any sustainable hint that the amount of
presence is related to advantages in detecting faults at all.
Discussion: We assume that monitoring in process plants can be separated
in two sub-processes: one component that can be solved with conventional
2D visualizations and another component that require 3D visualizations
like surface plots in order to solve more complex problems. Our findings
show that in this case the visualization should start with the problem
in front of the operator and should than depart subsequently.
Further research deals with the relation between attention efforts
(measured through work load) and task solution.
Practical Relevance
The impact and benefit of 3D visualization in
process plant operation is discussed. We assume that spatial
presentation of a sensor field as surface plot is more efficient to
monitor a process and to detect faults (in terms of time and number)
than 2D visualizations. If faults could be detected earlier and
appropriate measures could be taken, the cost reduction for operation
will be tremendous, due to the avoidance of down-times.
The discussed 3D presentation has been introduced already in an
industrial plant successfully.
Development and validation of scales assessing different job-related
self-control demands (Vol. 1 – 2007)
Author: Barbara Neubach und Klaus-Helmut Schmidt
Keywords:
· job demands ·
emotion-control · burnout · self-control
Summary
Changes in the modern
world of work have created new job demands. Nowadays employees are
increasingly expected to be self-responsible for their work results, to
react flexibly touncertainties and to behave in an achievement- and
customeroriented way in order to contribute to the success of the
company. All these demands require self-control insofar as the
individual must behave in accordance with the companies’ interests and
goals and at the same time suppress any spontaneous behaviour which
deviates from the expected one. People exert self-control, for example,
when they conform their behaviour to given standards, express
organizationally desired emotions, or avoid distractions and overcome
barriers to pursue an externally determined goal. Results of basic
research suggests that the exertion of self-control is associated with
psychic costs. For example, Muraven, Tice, and Baumeister (1998)
demonstrated that after an act of self-control performance on a second,
unrelated act of self-control was impaired. In one study, they showed
that thought-control caused people to give up faster on a subsequent
anagram task than those of a control group. In another study, an
emotion-regulation exercise resulted in subsequent decrements on a
physical endurance task. This and other findings provide strong support
for the hypotheses that different acts of self-control all draw on a
single limited resource, and that consecutive exertion leads to
exhaustion of this resource. Research on emotion work provides initial
evidence that workplace-related self-control might be a stressor. The
studies currently available show that the expression of organizationally
desired emotions has negative effects if emotional dissonance exists
(Zapf 2002). Emotional dissonance occurs when someone’s true emotions
conflict with the emotions he is required to display in a particular
situation. In this case, displaying appropriate emotions requires
intrapsychological processes to suppress or control spontaneously and
genuinely experienced emotions. Under this point of view emotional
dissonance could be interpreted as one aspect of self-control - as
self-control of emotions. To investigate self-control at the workplace
more directly, Neubach and Schmidt (2006) have recently developed a
scale ‘required self-control’. The scale covers the suppression of
spontaneous, impulsive reaction tendencies. Neubach and Schmidt (2006)
showed, that required self-control and emotional dissonance reflect
factorially distinct and only moderately related constructs. Significant
correlations were found between ‘required self-control’ and strain.
Schmidt and Neubach (2006) replicated this result with a different
sample. To differentiate the measurement of self-control at the
workplace, in the present study two additional facets of self-control
were operationalized. According to theories of volition (Goschke 1997;
Sokolowski 1996) and results of basic research (Muraven et al. 1998;
Baumeister et al. 1998) we constructed the scales ‘resisting
distractions’ and ‘overcoming inner obstacles’. The scale ‘required
self-control’ was slightly modified to focus on ‘impulse-control’. 549
employees of an administration of a German federal state participated in
the study. 15 Items were used to measure facets of self-control. The
results of a principal component analysis followed by a varimax rotation
showed a clear three-factor solution with simple structure. The first
factor comprised six items that measured ‘impulse-control’, the second
factor was composed of five items describing ‘overcoming inner
obstacles’, and the third factor contained four items asking for
‘resisting distractions’. The internal consistencies of the scales were
good. Cronbach’s alpha ranged from .87 to .90. Correlations with task
variables and strain variables provide support for the discriminant and
convergent validity of the self-control scales. Furthermore,
hierarchical moderated regression analyses were conducted to assess the
unique contribution of each self-control scale on strain variables. The
results indicate significant main effects of ‘impulse-control’ and
‘overcoming inner obstacles’. Even when entered into the regression
after social and task variables, ‘impulse-control’ and ‘overcoming inner
obstacles’ showed significant beta weights. No main effect appeared for
‘resisting distractions’. This could be due to an overlap between
‘resisting distractions’ and the task variable workload. The results
confirm findings from previous studies on ‘impulsecontrol’. To assess
the sensitivity of the scale, scores of impulse-control was compared in
three different samples (geriatric nurses, employees of a municipal
administration, and employees of an administration of a German federal
state). The hypothesis was that geriatric nurses display a higher level
of impulse-control. This was assumed because caring for residents with
dementia or depression requires extreme patience and perseverance, and
because dealing with emotionally demanding situations (e. g. death and
dying) requires a large amount of emotion-control. Statistical analysis
revealed that, on average, impulse-control scores for geriatric nurses
were significantly higher than impulse-control scores for administration
employees. This result supports the ecological validity of the scale
‘impulse-control’. All in all, the results confirm that the scale
impulse-control is reliable and valid. The results for ‘resisting
distractions’ and ‘overcoming inner obstacles’ need to be replicated and
cross-validated.
Practical Relevance
The developed scales
of self-control allow specific assessments of a novel stressor from an
occupational psychological perspective. Taking into account the
increasing requirements for efficiency and flexibility further
investigation seems warranted.
Vol. 2
- 2007
Dual-task performance while
driving a car: Age-related differences in critical situations
(Vol.
2 – 2007)
Author:
Gisa Aschersleben und Jochen
Müsseler
Keywords:
dual-task situation, stimulus-response-compatibility, older drivers
Summary
Dual task
situations are ubiquitous, at home as well as at work. Especially modern
information technologies often require the coordination of different
activities. For example, while driving a car the driver has to process
additional information (e.g. from the navigation system, from the
walkie-talkie or from the mobile phone) and to react in an appropriate
way. This is especially the case for professional drivers like taxi
drivers or lorry drivers. Under less demanding driving conditions, e.g.
slow driving with low traffic density, the coordination of the primary
task (driving the car) and the secondary task (manipulating the
navigation system) might be relatively easy. However, under demanding
driving conditions and especially in critical traffic situations,
impairments in reaction times and driving errors can be expected. Dual
task conditions are in particular demanding for older drivers as has
been demonstrated in many experimental studies. Another important factor
is the cross-task compatibility that is whether the information
presented in the second task provides information, which is compatible
or incompatible to the primary task. In first experiments using a
driving simulation set-up we tested groups of younger (age: 18 – 30
years) and elderly (age: 56 – 65 years) drivers in their reaction times
and error rates in dangerous situations (a person suddenly jumping on
the street, which requires a sudden reaction with the steering wheel).
First results indicate that effects of cross-task compatibility depend
on the relevance of the driving situation and on the direction of the
response that has to be performed in the primary task and not so much on
the position at which the information is presented. Moreover, although
the groups of elderly participants show increased reaction times they do
not seem to be especially impaired by compatibility effects. This
finding might be a result of the increased
amount of expertise in older drivers.
Practical Relevance
Information from
a driver assistance system (e.g. a navigation system) often requires to
react immediately thus introducing a secondary task beneath the main
primary task (driving the car). The study examines with younger and
elderly professional drivers whether and how driving is impaired by
dual-task demands, especially in critical situations. Based on the
findings we plan to propose guidelines and recommendations for the
age-based design of operation devices in vehicles and to suggest
training programms for older drivers.
Perceived strain and well-being in different types of offices (Vol. 2 –
2007)
Author:
Lukas Windlinger und Nina Zäch
Keywords:
wellbeing, work environment, strain, office design
Summary
Office work
places typically entail conditions in the working environment that can
hardly be influenced and controlled by the users. The most important of
these conditions is environmental noise. Environmental noise can be
disturbing and distracting. In the present research, perceived
environmental strain is analysed in large and small offices. Further,
the effects of environmental strain in offices on wellbeing are
analysed. Noise in offices is mostly caused by conversations of
colleagues. Conversations can be disturbing and distracting on the one
hand, on the other hand they can act as a resource. Unhindered
communication in large offices enhances social support and contributes
to stronger cohesion in workgroups. Social climate is therefore analysed
as well. Relevant organisational conditions are included in the research
as control for two reasons: (1) individual conditions are influenced by
many factors of the work system, and (2) the control guarantees the
comparability of the employees in different types of offices. The
allocation of employees to different types of offices is usually based
on functional and status related reasons. Comparisons between employees
in different types of offices therefore are meaningful only when work
related organisational conditions are controlled because these
conditions define control latitudes which are reflected in work
organisation and work design. In previous research on environmental
strain an well-being in offices, however, organisational conditions have
not been controlled. A written questionnaire was administered in two
financial service providers. Subjects with a degree of employment of
less than 80% and subjects that occupied their office workplace in less
than 80% of their working time were excluded from the sample. The final
sample consists of 51 subjects. All participants work in the same jobs
in the same divisions. In each of the two companies, the participants
work in different types of offices in the same building. There were no
differences between the two companies, nor in sex, age and jobs between
the two office conditions. No difference was found in work content and
work conditions between the two office conditions either. Results show
that perceived strain caused by noise is significantly higher in large
offices compared to small offices. Among all environmental strains,
noise is most prevalent: in both office types nearly 60% of the
participants reported medium to high strain caused by nvironmental
noise. Telephone conversations and conversations by colleagues were
referred to as the most frequent sources of noise. Perceived
distractions were significantly more frequent in large offices. Further
statistically significant differences occurred in perceived strain
through visual stimuli and through aircondition. In all cases the large
office group reported more strain than the small office group. The
differences in perceived strain are not paralleled in differences in
measures of well-being. Considering middleterm effects on well-being,
however, the large office group shows a more pleasurable social climate.
On the other hand, the small office group experiences more mutual social
support. These results suggest a possible qualitatively different
development of social relations, depending on size and spatial
structures in offices.
Practical Relevance
The design of
office environments has effects on well-being, social climate and
satisfaction of the users. The systematic analysis of these effects and
the knowledge of causal influences contribute to improved design of
office environments on the macro-ergonomic level.
Evaluation of instruments to evaluate job satisfaction (Vol. 2 – 2007)
Author:
Yvonne Ferreira
Keywords: job
satisfaction, job satisfaction measurement, concept of job satisfaction
Summary
In the following
article the results of a study of instruments of job satisfaction are
presented. Given the fact that on one hand the construct of job
satisfaction is still of major interest there is on the other hand at
least scepticism regarding the reliability and validity of the present
evaluation instruments. The initiation of this research was the failure
attempt to use an already existing questionnaire for the evaluation of
job satisfaction as valid criteria for the development of a new
instrument. Hereby the instability of the postulated factors became
obvious. All in all over 300 instruments to evaluate job satisfaction
could be determined. As a restriction it must be noticed that foreign
instruments, if not published in English or German language, could only
be considered in a few cases. In the following research 201 instruments
could be adopted.
1. To permit a
comparison between the investigated instruments, eligible criteria have
to be determined: Four minimal requirements have been defined to
integrate as much instruments as possible in the evaluation (cf. for
example Lienert and Raatz 1994). With a close approach to job
satisfaction should all common definitions of job satisfaction be
enclosed (cf. Ferreira 2001).
2. Application of
the instrument within a norm sample of at least 100 persons
3. Investigation of
the instrument regarding the quality factors of reliability and validity
(the question of objectivity remains unconsidered, because nearly all
given instruments were concerned questionnaires)
4. Availability of
the instrument (publication)
The research and
categorisation of job satisfaction instruments shows that during and
especially after the conception process of the instruments scientific
criteria was often not respected: Instruments have not been tested on a
sufficient number of subjects, quality factors have not been calculated,
the development was not based on a theory or own concept and further
more. The reason for this could be that lots of instruments were either
constructed for academic research or as an answer to specific
organisational questions. In addition to the limitation of existing
measurement instruments, the application of factor-analytically
extracted instruments for job satisfaction evaluation could at least be
challenged. As a result of this, the lack of prove of the correlation
between job satisfaction and other factors could be due to the used
measurement instruments or due to the postulated correlation. If on the
one hand the correlation between job satisfaction and other factors and
on the other hand the deployed evaluation instruments are at least
questionable, this can be the reason to intensify the studies in both
research areas. The aim of this research, to create more humane and
economic workplaces, is not only worthwhile but has also socio-political
and economic brisance (cf. among others Hamm 1999). It is very important
to discuss and to show job satisfaction in other theoretical contexts.
There is a large number of approaches to extend and to improve the
concept of job satisfaction, e.g. by integrating other concepts as
emotions and commitment (cf. e.g. Fischer 2006, Wirtschaftspsychologie
2005). From a scientific point of view, those developments are very
promising and give hope for improved instruments.
Practical Relevance
Job satisfaction
is a popular construct especially at operational leve. The correlation
between economic factors as for example quality, time of absence, and
performance are postulated.
Learning Cultures and
Different Perceptions of Learning-Conducive
Working Conditions
in Five
Businesses – Research
Results (Vol. 2 – 2007)
Author:
Erika Spieß, Ralph Woschée und
Brigitte Geldermann
Keywords:
·Learning cultures, development of competence, job satisfaction,
learning-conducive working
conditions
Summary
The project „new
learning cultures in organizations“, part of the BMBF program „Learning
Culture – Development of Competence: Learning in the Work Process“,
accompanied five company projects to develop personal and organizational
competence from 01/01/2001 to 31/12/2003. In the course of changing
organizational and career models, employees change workplaces more
frequently, individual learning needs increase, becoming more
specialized and complex. Standardized intensive further education
courses can no longer meet these needs. However, the necessary greater
staff participation in organizing the work process presupposes that
learning opportunities are available. A central assumption was that
measures for developing employee competence in the company would result
in a learning culture that is perceived to be learning conducive and
thus lead to job satisfaction. The project was based on theoretical
concepts of developing competence, self-organized learning and learning
culture. The heart of learning competence are the individual’s
selforganization abilities. Competence is considered to be a disposition
to be able to self-organize. Growing self-organized learning at the
workplace therefore influences the role of the superior within the
company: the superior has to support these new learning processes
actively. A central prerequisite for developing employee job competence
is a corresponding learning culture within the company that makes this
possible and promotes it. „New learning cultures“ refer primarily to
learning activities and a setting in which learning occurs. Superiors
become important moderators in establishing a corresponding learning
culture in companies. Based on this, the research projects assumed the
following:
1. Companies differ
regarding conditions for employeecompetence development.
2. Due to current
developments in companies, superiors have to assume the role of a
supporter and promoter of learning in employee self-organization. As a
consequence of the different role functions, the superior’s and the
employee’s perception of the learning conduciveness of working
conditions for employee competence development, however, is not the
same.
3. Perception of
learning-conducive working conditions and job satisfaction are
positively correlated. The heart of the survey were questionnaires on
learning- relevant features of the job and on learning in the work
process. Competence-building measures comprised developing superiors’
and employees’ competence by means of teamoriented action, discussing
company targets, introducing a system of agreeing on targets and
introducing a program for developing technical competence as well as
introducing a yearlong program for long-term further development of
organizational and staff competence. An important outcome was that the
learning cultures of the five companies differed as did the superiors’
and employees’ subjective perceptions of the learning conduciveness of
working conditions. The employees rated the work beneficial learning
conditions from their vantage point and the superiors from theirs. The
employees’ and the superiors’ perceptions of the conditions for
developing employee competence varied significantly: the superior always
overestimated staff conditions. Moreover, job satisfaction and learning
in the work process correlate positively.
Practical Relevance
For the
company, the outcome means creating a good learning culture is very
important for employee job satisfaction. Changing the learning culture,
however, is a slow, weary process in which superiors play a significant
role and assume a model function. The aim is to develop a learning
program that widens the scope of the job and promotes the versatility of
requirements and transparency of processes. Offering an ability to
participate and to develop contributes to staff satisfaction. spiess
woschee geldermann.pmd 04.06.2007, 09:26 28
Vol. 3
- 2007
Development of Work
Physiology and Ergonomics in Germany —Tasks and Objectives in Education
and
Research (Vol. 3 – 2007)
Author:
Helmut Strasser
Keywords: Work
Physiology, Work Science/Ergonomics, Physiological Costs
Summary
Work physiology which was
established as a scientific discipline in Germany around the turn from
the 19th to the 20th century, when the focus was on basic investigations
into physical work and the human metabolism, became the germ cell of
todays widely-spred work science and ergonomics. But it was a long way
until in the sixties, several chairs and research institutes for work
physiology, work science, and ergonomics had been founded mostly in
faculties of mechanical engineering at Technical Universities. It is
remarkable that the first generation of the full professors and most of
the renowned founders of ergonomics had been working and had acquired
their fundamental scientific education in the world-famous
Max-Planck-Institute of Work Physiology in Dortmund. Meanwhile, there is
no doubt that the ergonomic design of workplaces and the appropriate
sensoric and motoric interfaces in a man-machine system according to the
principle „man, the measure of all things“ would not correctly be
possible if fundamental work-physiological knowledge of the
characteristics of man, i.e., the capacities as well as the limitations
of the human sensory organs and the hand-arm system, were not
considered. Nonetheless, work physiology as a discipline in Germany has
lost somewhat in popularity during recent years. This may be due to the
fact that on the one hand basic knowledge has found meanwhile its way
into generally applicable teaching and guiding principles of work
science, and ergonomics, respectively, and on the other hand that
effective research utilizing work-physiological methods needs years of
experience and mostly deserves intensive and hard working as well as
precisive working hypotheses and strategies. Yet, a type of working
associated with something like „blood, sweat and tears“, of course, is
not as popular in a new generation of researchers as experiencing „fun
at work“, and getting fruitfull success, well in time via less strenuous
and more softly methods. But in ergonomics research, never all claims
may be given up to develop and apply methods which allow to measure
„physiological costs“ of work. Assessing the ergonomic quality of, e.g.,
hand-held tools and computer-input devices solely by expert rating,
„paper and pencil“ tests or subjective ratings could be insufficient and
misleading. In order to clearly quantify what has to be invested or
„paid“ by the musculature involved in work when utilizing more or less
ergonomically designed tools, also physiological measures such as
multi-channel electromyography have to be applied. Similar is true for
evaluating noise exposures who’s physiological costs exactly can be
quantified in „figures and numbers“ by measuring threshold shifts, and
their restitution if there are still reversible and not already
irreversible physiological responses associated with noise. So,
comparable to work-related heart rate increases and their restitution
after work as specific physiological responses to dynamic muscle work
during classical work-physiological investigations, also in the future
it will be crucial in ergonomics to apply objective, reproducible,
specified and valid experimental methods and to address concrete
questions which always require a clear commitment to working on details
as it was and is the case in work physiology.
Practical Relevance
Comprehensive
work-physiological knowledge of the characteristics of the human
organism, always was, and will still in the future remain, a
prerequisite for the truly ergonomic design of workplaces and
user-friendly tools and products. Besides physiological core
competencies for a competent ergonomics education, work-physiological
principles and paradigms are absolutely necessary for ergonomics
laboratory research approaches as well for integrative applied field
research aiming at the analysis, assessment and humanoriented design of
the working environment.
Room acoustics for open-plan offices (Vol. 3 – 2007)
Author:
Helmut V. Fuchs
Keywords:
Open-plan office, noise control, sound absorber, sound barrier,
communication
Summary
Noise in open-plan offices,
schools, lobbies, restaurants and other communication areas is
predominantly self-generated by their respective users. The lack of
appropriate sound absorption in traditionally furbished classrooms and
scarcely furnished modern office environments forces all occupants to
inevitably raise their voices, as soon as the necessary communication
among them or/and on the phone sets in. Conventional damping at medium
and high frequencies by means of absorptive furniture and screens may
somewhat reduce the detrimental effect of the room on speech
intelligibility and the resulting noise development. Current research,
consultant and restoration activities have, however, revealed that novel
low-frequency, yet broadband sound absorber modules can tackle this
problem more efficiently. The new room acoustic concept was earlier
described more fundamentally in „Relevance and treatment of the low
frequency domain for noise control and acoustic comfort in rooms“ (Acta
Acustica 91 (2005), p. 920-928). Numerous refurbishment projects for
meanwhile more than 100 000 valuable workplaces showed amazing
improvements of their acoustic comfort in enclosures where more
conventional noise control measures had failed or were impracticable for
several reasons. A more rigorous acoustic treatment of rooms with high
communicative demands has gained considerable attention for three
reasons:
♦ Acoustically „soft“
outfits with carpets, curtains, upholstery and acoustic ceilings,
plasterwork, baffles or sails have completely gone out of fashion, not
only but mainly for utility reasons.
♦ Acoustically „rigid“
concrete, stone and glass surfaces are not only considered as an
indispensable part of modern architectural design but also form the
necessary presupposition for construction elements to be thermally
activated.
♦ For up-to-date
administration, business, education and communication centres tolerable
noise levels and high speech intelligibility have become important
ergonomic qualities, the absence of which increasingly provokes severe
criticism and complaints from users as well as frominvestors.
An always prevailing lack
of space and shortage of resources hardly ever led to a well-balanced or
even low-pitched acoustic treatment of, in particular, the smaller or
flat rooms. It may therefore come as a surprise for many a skilled
acoustician that one may now - with relatively simple measures and at
moderate costs - cope with the long-standing low-frequency problems by
employing especially developed building elements of a novel, visually
attractive design. The concentration of millions of work places
especially in openplan offices definitely exceeds ergonomic limits, as
the noise generated by its users unavoidably reaches intolerably high
levels of occasionally more than 80 dB(A). Following traditional
concepts, one tries to damp the sound generated through multiple
communication processes within the room by means of absorbent ceilings
and conventional office dividers. This, however, is now in conflict with
up-to-date trends towards thermal activation and visual transparency of
all bounding surfaces. Above all, these out-of-date acoustic measures do
not tackle the problem at its roots, i.e. at the vivid sound sources, as
may be concluded from numerous negative experiences. Acoustic comfort
and noise control as indispensable presuppositions for concentrated
intellectual work can only be achieved, if equally low reverberation of
the room down to very low frequencies supports best speech
intelligibility. Novel high-performance broadband compact absorber
modules and fully transparent sound screens completely incorporating
such modules now enable an optimal visual and acoustical layout for
truly open-plan offices. The article shows the visual differences of the
innovative as compared to the conventional acoustic treatments in
openplan offices and describes the respective efficiency of two
alternatives in terms of the
♦ pressure level decay from
an artificial „pink noise“ source along measuring paths spanning the
bureau landscape as a whole as compared to that in a „free field“ (with
no reflections) and
♦ reverberation time
measured as a function of frequency. After this acoustic dilemma could
be solved very convincingly in prominent cases, many fallow lying office
immobilia may be revived for open-plan (group- or team-) office
landscapes with only 6 to 12 m2 floor area occupancy per user. With
their high flexibility and relatively low price the proposed innovative
measures can help to raise the value of numerous objects – attractive
aspects for clear-sighted project developers and investors in a fast
growing market.
Practical Relevance
The often deafening noise
in service centres generated by the users themselves can be lowered by
more than 30 dB(A) by employing novel sound absorbing and shielding
glass dividers with integrated broadband sound absorber modules – a
practicable guideline for a persistent revalorization of many fallow
lying office immobilia.
The influence of milking parlour equipment on the workload of the milker
(Vol. 3 – 2007)
Author:
Martina Jakob, Sandra Rose und
Reiner Brunsch
Keywords: Work
load · strain · milkers · musculoskeletal disorders · motion analysis ·
body posture analysis
Summary
The technical development
in milk production has lead to changes in milking parlours concerning
the workload of milkers. Physically demanding work tasks have become
less, but at the same time the variety of tasks has decreased. Modern
milking parlours are functioning highly efficient. One of the remaining
physically demanding tasks is attaching the milking unit; strain depends
on its weight, the task duration as well as the body posture. The body
posture is influenced by the size of the person and the distance between
the worker and the udder. The results of an evaluation of temporary
disability data showed a significant number of female milkers being
absent due to musculoskeletal disorders (Liebers & Caffier 2005). A
swedish long term survey also reported a raise in discomfort among
milkers (Pinzke 2003). This is contradictory to the actual decrease of
physically demanding work during milking. The objective of this study
was to analyse the actual work routine and the influence of several
factors like the equipment and the work style. For this the body
postures were measured with a motion analysis system (Simi Reality
Motion Systems, Germany) in two different milking systems (Herringbone,
Side-by- Side) while the milker was attaching the cluster. The applied
motion analysis system was based on video tracking of the work process
and the consecutive generation of 3-Droom- coordinates calculated from
marker positions on the worker’s body. The marker positions were
determined from two videos for each frame by tracking algorithms of the
software. The postural analysis brought up that it is necessary to bend
forward, lift the arm and stretch it to be able to reach the teats. The
arm holding the cluster showed constant values for the duration of the
work task, but also variations of 10° within the same setting. The
strain on the arm depends on the cluster weight and the upper arm
elevation. The moment of torque was calculated for a light and a heavy
milking cluster based on the measured length of the lever arm. The
attaching arm showed a dynamic progression during work; the variation
was larger in practice compared to the experimental setting. The exact
body posture depended on the size of the person, the work style, the
working environment and other parameters. For the herringbone milking
system the data variation tended to be larger. The herringbone is
characterised by a larger distance between the milker and the furthest
teat. The duration for attaching the cluster was also longer compared to
Side-by-side. It took round about 10 seconds from grabbing the cluster
until it was attached to the udder. The exposure analysis according to
DIN EN 1005-4 brought up extreme joint postures for the upper arm
elevation. The weight of the milking cluster is not regarded and
inevitably causes higher strain. There are some technical devices that
help to ergonomically improve the work task. It is possible to adjust
the floor height, service arms are available to hold the cluster and
take it off and indexing is used to move the cow in the right position.
Further investigations are planned to measure the impact of cluster
weight in combination with different body postures. The proposal of
ergonomic guidelines for the implementation of technical equipment in
milking parlours shall be achieved.
Practical Relevance
Appropriate work place
design to prevent disorders amongst milkers is based on the knowledge of
the work routine as well as factors that may cause disorders. The
presented results shall contribute to develop guidelines to implement
ergonomic devices to reduce strain and improve work place design in
modern milking parlours.
The effect of predictability of system response times on the user’s
behavior and state (Vol. 3 – 2007)
Author:
Werner Kuhmann, Florian Schaefer
Keywords: system
response times, predictability of work flow, user behaviour, user state,
human computer
interaction
Summary
How well do unexperienced
users estimate the length of enforced waiting periods in human-computer
interaction, and in which way does the predictability of such waiting
periods influence the working behavior and the psychophysical state of
the user? These were the central questions of a study in which simple
tasks were separated by waiting periods of 0.5 to 5.5 seconds and mean
of 3 seconds. Subjects performed so called ‘Sterzinger lines’ of letters
in random sequence in which targets had to be identified and marked by
the cursor. Each line contained a target which occurred in one of ten
possible positions within the line. Waiting periods were either coupled
with the target position, and thus predictable, or were randomly
distributed, and thus unpredictable. For predictable waiting periods an
additional experimental condition was introduced in which the length of
the waiting period was visually indicated on the screen. This display
was analoguos to a ‘bar display’: when the target was marked correctly,
the left-hand part of the line remained on the screen. After the ending
of the waiting period the next task was presented. In 20% the
presentation of the next task was, however, postponed until the user
pressed a ‘restart-button’ (Stop-Response-Time-Task, Stop-RT), with an
additional waiting period of 8 seconds. Pressing the restartbutton too
early, i.e. befor the waiting period was expired, therefore resulted in
an unproportional long additional waiting period, and thus in prolonged
working time. Response times in the Stop-RT-Tasks thus give an estimate
of the internal representation of the length of waiting periods. The
results show, that Stop-RTs of the subjects under the predictable
conditions corresponded with the target positions of the preceeding
task. For subjects working under the unpredictable condition Stop-RTs
were uncorrelated with the target position and exceeded the longest
waiting period. Obviously, subjects under the predictable conditions
tried to optimize their Stop- RT-response-times and to respond
differentially to the length of the waiting periods. Subjects under the
unpredictable condition followed the longest of the waiting periods in
the Stop-RT-tasks. Both strategies, differential responding and
responding to the longest waiting period, indicate that subjects tried
to optimize the total amount of working time. Differential responding
under predictable conditions, however, was associated with an additional
cognitive work load as compared to concentration upon the longest
waiting period only under the unpredictable conditions.
Practical Relevance
In modern software design
it is well established to support the users with information about
actual status of the task perfomed and time to completion of the task.
For example, the status is displayed as a moving bar, and the completion
time is calculated and displayed in minutes and seconds. Completion
times represent waiting periods for the user, which usually are called
‘system response times’. When deciding which display of system response
times during human-computer interaction should to be used one has to
consider weather the predicted time intervals are basically computable
due to their regularity or if they cannot be calculated due to that they
depend on external factors. The results of the present study show that
in the first case the user is able to detect these regularities by
implicit learning and thus to optimize his or her work flow according to
the system’s timing behaviour. In this case the additional visual
display is of no use and may even irritate the user. In the second case
– when the system response times cannot be calculated and are
unpredictable – a display of predicted waiting periods lacks accuracy
and thus is less helpful. Therefore, a display of actual progress should
generally be preferred.
Promotion of Changing Processes by Efficient Team Management in a
Company Health Insurance Scheme (Vol. 3 – 2007)
Author:
Stefan Beyer, Hans-Jörg Gittler,
Barbara Neubach und Klaus-Helmut Schmidt
Keywords: Health
insurances, organizational development, teamwork, productivity of work
groups, ProMES
Summary
The general development of
the health insurance market, decreasing financial resources and
increasing competition pressure, necessitate a reorientation of
compulsory health insurances in Germany. In the future, a health
insurance company’s success will increasingly be determined by the
ability to realize continuous improvements of productivity and to
guarantee good service and product quality. Health insurances must also
be able to react flexibly to changing legal duties or competitive
conditions. In this regard, team based structures have more innovative
potential than hierarchically and functionally divided structures. The
answer to the question whether the introduction and use of teamwork in
fact lead to the desired effects, depends on numerous variables and
limiting conditions which have to be considered during the introduction
and further development of teamwork. The present article describes how
BAHN-BKK, an important company health insurance scheme, introduced team
structures in its regional branches through a multi-staged organization
development process. During the first stage the company improved the
surrounding conditions to encourage performance. The second stage
entailed purposeful training measures to support the formation of teams,
while the third stage introduced a Productivity Management and
Enhancement System (ProMES), giving the teams a useful tool to develop
strategies and measures in order to improve their productivity and to
help the people do their work. The results of a concurrent research
project confirm that the use of ProMES allowed the teams to improve
customer orientation, economic efficiency and work efficiency in a
pragmatic manner. The verified results showed improved productivity and
quality in most cases. By determining major areas, deploying delegates
during the development process and introducing employees gradually to
all relevant sectors, the management of BAHN-BKK was able to treat the
resources of decision makers and the project participants with care.
Furthermore, opposition and problems of acceptance could be identified
and removed in order for the changing process to be persistent.
Practical Relevance
The field report provides
an example of how enterprises can be enabled to arrange important
preconditions for efficient teamwork applying a multi-staged
organization development process. The report also confirms that the
management system ProMES introduced to support team processes provides
an appropriate basis for measuring performance, collecting systematic
feedback and fostering target agreement. The use of ProMES thus
guarantees comprehensive enterprise objectives to be converted into team
actions. Additionally, the stability and efficiency of team processes
can be improved, creating an atmosphere of learning, development and
innovation.
Vol. 4
- 2007
Continuous head gestures – an alternative way of controlling menu based
in-vehicle information systems? (Vol. 4 - 2007)
Author: Claus Marberger und Michael Kondzior
Keywords: User interface, gesture control, head orientation, head
movement, multifunctional controller, menu
systems
Summary
Infotainment systems inside modern vehicles
include a great number of features such as multimedia players, car
diagnosis systems or communication functions. In order to keep these
systems usable and safe while driving special care needs to be taken for
the user interface design. Multi-functional Rotary-Push Systems (RPS)
seem to become a standard input device for controlling these kinds of
systems in Europe and the USA (Rößger & Hofmeister 2003). However, from
an ergonomic point of view this user interface concept has also
weaknesses which cause usability difficulties for many drivers. This
report describes an experimental study that compares an alternative
interaction concept based on continuous head gestures against the
standard approach using a rotary-push-device. The new concept utilises a
sensor that measures the driver’s head orientation in real time. This
parameter can be used to control a pointer or to highlight an area on
the central screen. The confirmation of a highlighted area can be
achieved by pressing a simple button at the steering wheel. A
theoretical analysis of the head gesture based interaction concept
reveals potential advantages: First, the homing operation (moving
finger/hand towards the input device) should be simpler and take less
time (mainly looking at display vs. moving hand towards
rotary-push-device. Second, the hands don’t need to be taken off the
steering wheel for controlling the graphical user interface on the
central screen. Another advantage over the rotary-push-device is that
the movements of the head are compatible with the graphical feedback of
the system. This is not the case with rotary-pushdevices since turning
the device clockwise often causes system reactions either up or down.
However, there are also potential disadvantages of the head based
concept: Since there is no haptic feedback the interaction may capture
more visual attention than the (haptic) rotary controller. The
experiments covered various comparisons between the head based
interaction concept and the RPS concept in terms of ♦ driving
performance (while interacting with the system), ♦ task performance
(while driving) and ♦ subjective criteria such as mental effort and
acceptance. Both interaction concepts were implemented in the immersive
driving simulator run by Fraunhofer IAO. 10 subjects (8 males, 2
females) took part in the experiment. The primary task was to drive a 40
km stretch of highway at a speed of 100 km/h while performing a
specially designed secondary task. The graphical user interface of the
secondary task was based on an abstract menu with six buttons at each
level. Following a within-subject design the task was to select a series
of buttons with a particular given number either by head movements
(experimental condition) or by turning the rotary-push-device (control
condition). The order of the conditions was counterbalanced to avoid
learning effects. All participants were able to practice each interface
concept while standing still and also while driving. The results related
to driving performance can be summarised as following: The Standard
Deviation of the Driving Speed (SDDS) while performing the secondary
task did not significantly differ between the interaction concepts
(Wilcoxon, z = -1.274, p(2-sided) = .232), nor did the Standard
Deviation of Lateral Position (SDLP) (Wilcoxon, z = -0.968, p(2-sided) =
.375). However, the mean values were slightly smaller for the RPS
condition. The results related to secondary task performance showed that
task completion time increased by 10% when using head movements as input
method. This difference was statistically significant (Wilcoxon, z =
-2.701, p(2-sided) = .004). Also the number of input errors increased
significantly by an average of 0.3 errors per task when using head
movements as input device (Wilcoxon, z = -2.620, p(2-sided) = .008).
Looking at subjective criteria the results revealed that the perceived
mental effort was significantly higher in the head control condition
(Wilcoxon, z = -2.703, p(2-sided) = .004). Mean RSME (Rating Scale
Mental Effort: Min=0, Max=150) values differed by approx. 30 units (RSME
head control: 75.5 vs. RSME rotary-push-device: 46.7). Finally,
acceptance ratings showed a tendency that interaction with the
rotary-push-device was perceived as being more useful and satisfactory.
In summary, the obtained results are not in favour of using continuous
head gestures. This effect can hardly be attributed to technical
shortcoming of the head tracking technology since real time performance
and optimal calibration was guaranteed for each subject. Only the
difference in training (rotary-push-devices were more familiar than
continuous head gestures) could explain the obtained results to a
certain degree. However, high mental workload (RSME) values suggest that
the head control interaction mode was visually more loading for this
type of task. Further research will reveal whether simpler tasks (e.g.
vertical scrolling in only one list or simple horizontal selection
tasks) can bring out the potential advantages of the head based
interaction mode.
Practical Relevance
Multi-functional central controllers (e.g.
rotary-push-devices) are becoming more and more a standard for
controlling menu based information systems inside the
vehicle. However, the rotary-push-device has clear weaknesses from an
ergonomic point of view. It is therefore essential to develop and
evaluate new interaction concepts in order to ensure a more comfortable
and safer use of in-vehicle information systems, especially while
driving.
Binocular coordination of eye movements in viewing conditions of head-up
displays in road vehicles (Vol .4 - 2007)
Author: Wilhelm Bernhard Kloke, Wolfgang Jaschinski, Gerhard
Rinkenauer
Keywords: Head-up display, eye movement, vergence.
Summary
Since several years, the automotive
industry has promoted the use of head-up displays for the presentation
of information in road vehicles. For head-up displays the windscreen is
used as a mirror to present information at a virtual location above the
vehicle’s front end, which is close to the main viewing direction. When
head-up displays are used to display the velocity, this information
appears at a larger viewing distance than when the conventional location
of a speed-indicator is used. These designs can be compared for
ergonomic differences. Among the advertised advantages of the head-up
display setup it has been supposed that a smaller change in viewing
distance relative to the front traffic could reduce the strain of the
driver's ocular system by reducing the need for accommodation and
vergence.
Fast ballistic eye movements (saccades) are usually performed when
changing the focus of attention from one object to another.
Simultaneously, the vergence angle between the visual axes of the two
eyes may have to be changed to adjust for the difference in depth. It
has been observed in previous studies that a changes in vergence may be
facilitated when they are executed in conjunction with saccades,
especially when both changes are combined in an ecologically valid way.
However, in these previous studies considerably large saccades and near
viewing distances have been used, thus the results of the studies cannot
be generalized to head-up displays. Therefore, the experiment in our
study has been designed to measure the vergence dynamics during fixation
changes in head-up display situations. For this reason two conditions
were simulated in our experiment: First, moving the eyes from the road
traffic to the conventional location of the speed-indicator and back
again. Second, moving the eyes from the road traffic to several
locations of the head-up display and back again. These locations
differed with respect to direction and required saccade size.
In our laboratory simulation, the dashboard was located at viewing
distance of 60 cm and a downward gaze inclination of 24°. For the
head-up display a viewing distance of 2 m was used at various positions
in the vertical and horizontal direction relative to the main direction.
The main direction consisted of the viewing direction to a screen in a
distance of 10m. This far distance corresponded to the traffic
situation. At the far distance a sequence of numbers was presented
randomly. After a certain number of digits the letter “S” indicated to
the participant to change gaze from the far distance to either the
speed-indicator position or to the head-up display. For the
speed-indicator and the head-up display position a simple nonius task
was used to assure correct fixation. For each of 8 experimental
conditions in 2 replicated sessions, the participants made series of 20
cycles of gaze change between the traffic and instrument positions. The
movements of both eyes were recorded using an Eyelink II system with a
sampling rate of 500 Hz. The vergence angles were computed as the
difference between the horizontal angles of the two eyes; the maximum
velocity of vergence change was computed in the different conditions of
convergence (far to near, i. e. from the traffic to instrument position)
and divergence (near to far, i. e. from the instrument position to the
traffic).
The observed maximum vergence velocity was higher for the change between
traffic and conventional position of the speed-indicator compared to the
change between traffic and head-up display positions; vergence velocity
was almost proportional to the difference in vergence demand. For the
divergent experimental conditions these velocities were about 30% lower
than for the convergent ones. Differences of vergence velocity between
the head-up display positions were generally small. No significant
difference between the horizontal or vertical directions were observed
for equal saccade sizes. For the downward positions of the head-up
display the vergence velocity was facilitated with increasing saccade
size. This effect was statistically significant, though small.
In sum, the time needed for saccade execution was sufficient to converge
to the correct vergence angle for both the head-up display and the
dashboard positions. Different possible locations of the head-up display
appear to have little effect on vergence performance. Our results show
that the vergence system is sufficiently prepared to cope with the
larger vergence demands of the gaze change to the conventional position
of the speed-indicator. If there are no limitations in accommodation the
results on vergence facilitation could support the assumption that the
accommodation is also facilitated to an appropriate degree, as vergence
is a strong stimulus for accommodation.
Practical Relevance
By use of head-up displays in road
vehicles, information such as the velocity indication is presented at a
different viewing distance compared to the conventional setup. This
induces different demands for the binocular coordination of the eyes
under conditions which are not covered yet by the experimental
literature. The results of our experiment simulating the conventional
speed-indicator position in the car dashboard and various positions of a
head-up display suggest that the advantage of the head-up displays for
the assistance of binocular eye movement coordination is rather limited.
Furthermore, the variation of the vertical position of the head-up
display showed a statistical significant effect on the observed maximum
vergence velocity. However, the small size of this effect, does not
support the notion that specific positions are preferable to others for
the matter of binocular coordination. Though the vergence demands were
higher for the conventional instrument position, participants were able
to compensate these demands by higher vergence velocities. Thus, the
reduction of vergence demands at head-up displays in road vehicles seems
not to be an ergonomic design issue of primary importance.
Evaluation of different mobile map displays for geographic orientation
tasks (Vol. 4 - 2007)
Author: Claudius Pfendler
Keywords: Head-Mounted Display, Workload, Simulator Sickness,
Visual Fatigue, Secondary Task
Summary
Military as well as civilian forces (e.g.,
police, ambulance) often face the problem of geographic orientation in
unknown areas, which increases the time for reaching the target
location. Especially in emergency cases this may result in serious
consequences. Orientation problems can occur e.g. in abandoned areas,
cities as well as within huge buildings, such as factories or airports.
In the experiment described in this paper three different types of
electronic displays were compared in respect to performance in an
extended geographic orientation task in which the subjects had to cross
a simulated virtual urban environment.
The visual simulation consisted of an interactive 3D scenario projected
on a screen in front of the subjects. The 2D maps for orientation were
displayed on one of the three electronic displays: a monocular
head-mounted LCD-display (HMD), a monocular head-mounted virtual
retinal-display with laser technology (RD) and a hand-held LCD-display
(HHD). The HMD as well as the HHD were polychrome, whereas the RD was
monochrome red. The task was to follow a given path shown on the map,
and to navigate through the urban environment. On the map the actual
position in the city was indicated by a moving dot. A joystick was used
as a control device to move across the urban area. Time to complete the
task – which took about 1.2 hours on average - was registered as
performance measure.
Peripheral attention was assumed to be higher with the HMD and RD as all
relevant information is permanently present in the visual field and
extensive eye and head movements are not necessary in contrast to the
HHD. To measure this effect, a secondary task had to be performed in
parallel to the primary task in which subjects had to detect digits (1,
2, 3 or 4) in the periphery of the visual simulation. Selection of the
digits, of the length of the interstimulus intervals as well as of the
location of the presentation were determined randomly. The subjects
responded with one of four corresponding buttons on the joystick.
Reaction times as well as percentage of errors, hits, and omissions were
measured as dependent variables.
As also effects from the displays on workload, simulator sickness and
visual fatigue were expected, these variables were assessed too.
Workload was measured with the NASA Task Load Index (Hart & Staveland
1988), which is based on bipolar ratings of mental, physical, and time
demands, as well as on evaluation of own performance, effort, and
frustration. As simulator sickness might be higher with HMDs, which
results, e.g., from dissociations between visual and vestibular stimuli,
the Simulator Sickness Questionnaire (SSQ) of Kennedy et al. (1993) was
also utilized in the experiment. Based on 17 ratings the questionnaire
provides scores for Nausea, occulomotor symptoms and Disorientation, and
a total simulator sickness score. Another problem with visual displays
especially in extended tasks is visual fatigue. In order to measure this
variable the Visual Fatigue Questionnaire (VFQ) of Bangor (2000) was
completed by the subjects, which comprises 17 ratings, addressing
symptoms like headache, dry eyes, difficulty focusing, nausea and mental
fatigue. The SSQ and VFQ were administered before and after the
experiment, so that values before the experiment, which might be already
elevated, could be taken into account by calculating difference scores.
At the end of the experiment subjects also completed a questionnaire
regarding experience with PCs, video games and joysticks. These data
were correlated with the experimental results.
In total 48 male subjects (mostly students) performed the task. The
subjects were randomly assigned to three groups (HMD,HHD, RD) from which
each one used only one of the displays (between subjects design).
Statistical analysis of subjective and objective data was based on
single factor ANOVAs (between factor=display with three levels: HMD,
HHD, RD).
The results show no significant differences between the displays. That
means that all displays lead to comparable performance, workload,
simulator sickness and visual fatigue levels in geographic orientation
tasks of the type investigated. Nevertheless, a series of consistent
trends were observed which conform to the hypotheses. In this respect
the HMD had the shortest completion times in the geographic orientation
task as well as the fastest reaction times, the lowest percentage of
omissions and the highest percentage of correct responses in the
secondary task. The average completion time with the HMD was about 10%
shorter than with the HHD. Obviously peripheral attention profits from
the advantage that all relevant information is presented in a single
visual area, so that extensive eye and head movements become redundant.
In contrast, the HHD shows the lowest levels of workload, simulator
sickness and visual fatigue. The results can be tentatively interpreted
as supporting the hypotheses of performance advantages of the HMD
whereas these advantages are accompanied with higher costs in terms of
workload, simulator sickness and visual fatigue. The RD scores are
usually worst in subjective and objective variables reflecting the
disadvantages of monochrome displays. With this display it is more
difficult to locate the own position on the map, but this interpretation
needs more empirical support.
With all displays workload was high, demonstrating that the effort
invested in the task was high. Also simulator sickness was high
regardless of the displays. Obviously there are at least two factors in
the experiment which might contribute to simulator sickness: The
simulation and the visual displays. The first contribution might result
from inconsistencies in the simulation like time delays between the
locomotion of the own position on the map and in the visual scenario.
Such factors seem to contribute more to simulator sickness than the
display, as also strong symptoms were associated with the HHD, which
should not produce simulator sickness. In contrast to the other
subjective data, visual fatigue was low in most aspects. Furthermore,
significant correlations between questionnaire data and experimental
results show that subjects experienced with video games have a better
performance in the primary and secondary task and rate the task lower in
respect to mental demands and effort.
Finally it must be pointed out that the conclusions must be supported by
further experiments with more sophisticated methods. E.g., instead of
the present secondary task with fixed presentation times for the
peripheral stimuli it is intended to use variable times. Apart from the
fact that it is a secondary task, the approach has much in common with
the determination of a recognition threshold with the method of constant
stimuli or an adaptive method and is assumed to be a better measure of
spare capacity left by different displays.
Practical Relevance
For geographic orientation of civilian and
military forces more and more mobile electronic map displays are used
while it is still not clear, which are suited best for this purpose.
That is why three displays (HMD, HHD, RD) have been compared in a
geographic orientation task with respect to performance, workload,
simulator sickness, visual fatigue, and peripheral attention. The
results show that the displays don’t differ significantly regarding
these variables and therefore no one can be preferred.
Evaluation of driver drowsiness by video analysis (Vol 4 - 2007)
Author: Axel Muttray, Lorenz
Hagenmeyer, Bastian Unold, Jean-Baptist du Prel, Britta Geißler
Keywords: Video analysis, sleepiness, driver
Summary
Introduction Video analysis of driver
behaviour is a means to evaluate the degree of sleepiness, using a
rating scale (Wierwille & Ellsworth 1994). In a field study, we
videotaped bus drivers in order to find out if Wierwille’s descriptors
were suitable to evaluate the sleepiness of these bus drivers. Because
the rating of video films is very time consuming, we compared Wierwille
method with two different methods which might be time sparing. The aim
of our pilot study was to evaluate if the methods are equivalent.
Methods Wierwille’s scale, a description of the wake-sleep continuum,
was translated into German. Then, we evaluated the descriptors by means
of video films of bus drivers. As high levels of sleepiness were missing
in these films, we completed the films with recordings from a driving
simulator experiment with sleep deprived subjects in order to cover the
whole sleepiness continuum. Wierwille’s scale descriptors were slightly
augmented and the visual analogue scale proposed was substituted by an
ordinal scale as such one could be easier managed by different raters.
The scale extends from 0 (awake) to 4 (very sleepy, including
microsleep), intervals are 0.25. Videos of six bus drivers and six
simulator drivers were evaluated by a trained rater (B.U.), the material
included more than 30 hours of video film. Three different analysis
algorithms for 5-minutes segments were compared. For algorithm 1, the
films were divided into 2.5-minutes segments, which were scored in a
randomised order. Then, the highest scores of pairs of chronologically
subsequent segments were used for calculation (algorithm 1, gold
standard). Algorithm 2 is similar to the procedure of Wylie (Wylie
1998). If the sleepiness score of the first 5-minutes segment of a
30-minutes epoch was < 1, the rater “jumped” to the first segment of the
next 30-minutes epoch. If the score was < 1, the rater “jumped” again to
the first segment of the next 30-minutes epoch. Segments that were not
rated were set to the score of the first segment of the according epoch.
However, if the score of a first segment was ≥1, all adjacent segments
were rated both forward and backward in time, until segments were found
with a score < 1. Algorithm 3 prescribed to view all segments with
double film speed. If signs of sleepiness were detected, only the
respective 5-minutes segments were scored with normal speed. In order to
calculate kappa, all values measured were divided into four subgroups.
Agreement between methods was also investigated by means of Bland-Altman
plots (Bland & Altman 1986).
Results Most segments were scored ≥ 1. Therefore, the alternative
methods did not save much time. For the comparison of algorithms 1 and
2, kappa was 0.67 (95 %-confidence interval (CI) 0.60 – 0.75). The
comparison between algorithms 1 and 3 yielded a kappa of 0.69 (95 %-CI
0.62 – 0.77). A kappa from 0.61 to 0.80 indicates a good agreement
(Altman 1999). This finding was supported by the Bland-Altman plots
which also showed a good agreement between the different methods.
Discussion The comparison between the methods showed a good agreement.
However, there are some limitations of this pilot study. Experiments
with a greater number of subjects are necessary in order to be able to
generalise the results. Furthermore, measurements of intra- and
inter-rater reliability are necessary. Our preliminary experiments with
two trained raters (L.H. and A.M.) point to a possibly good inter-rater
reliability, as the maximum difference of scores of video segments of
different drivers with a different level of sleepiness was 0.25. As the
agreement between the different methods was good, we conclude that
intra-rater reliability of the one rater was good, too.
Practical relevance
Driver fatigue is a major cause of road
accidents. Video analysis of driver behaviour is a means to assess the
level of sleepiness. This study is the first step to validate the
method. Video analysis may contribute to accident prevention. |