The Impact of Visual and Cognitive Dual-Task Demands on Traffic Perception During Road Crossing of Older and Younger Pedestrians.

With the help of the current experiment, we wanted to learn more about the impact of visually demanding vs. cognitively demanding secondary tasks on the attention allocation of older pedestrians during the phase of traffic perception within the process of road crossing. For this purpose, we used two different road crossing tasks as well as two different secondary tasks. The road crossing "stop task" was a signal detection task, where an approaching car had to be detected. The road crossing "go task" was a dynamic visual search task, where the resolution of a busy road situation had to be identified. The visual secondary task was a static visual search task and the cognitive secondary task was a 1-back (memory) task. One younger group (≤ 30 years) and one older group (≥ 65 years) of participants completed the tasks as single vs. dual-tasks in all possible combinations. Performance was measured through errors and response time; in addition, the subjective workload was assessed via NASA-TLX. Analyses show that the visual secondary task reduces performance in the road crossing more strongly than the cognitive task, while the visual task itself is less impaired by the road crossing tasks than is the cognitive task. Overall, performance diminishes from single to dual-task completion. Results further indicate age effects in terms of increased errors and response time for older compared to younger participants. In addition to these age effects, age-specific dual-task effects emerge for response time in the go task along with the visual task as well as for response time in the cognitive task along with the go task. Subjective workload is higher in the dual-task conditions than in the single tasks. Findings are discussed with regard to theoretical and practical implications.

Evaluation of an assistance system supporting older pedestrians' road crossing in virtual reality and in a real-world field test.

Older pedestrians are at a high risk of becoming victims of car accidents because they tend not to pay sufficient attention to upcoming traffic. Within our research project, an assistance system for older pedestrians has been developed. It detects the street and communicates with the users through a vibrotactile interface. Two evaluation studies have been carried out in order to understand the potential benefits and drawbacks of the developed assistance system. One study was conducted in a virtual environment (VR) with 23 participants, aged 65+. The other experiment was a field test in a real street environment with 26 participants, aged 65+. Objective dependent variables in both experiments were checking for traffic (operationalized via head tracking) and stopping in front of the street (VR study), i.e., approaching time (field test). Workload and acceptance served as subjective dependent variables. Analysis of the VR experiment showed significantly more head rotation with the assistance system than without it, as well as significantly more with cars than without cars. The same was true for the frequency of stopping. No significant difference was found concerning workload. With regard to acceptance, the majority of participants indicated that the system was supportive and able to reduce risks in traffic. In the field test, results for head rotation confirmed the findings of the VR study. Analysis showed a marginally significant higher head rotation frequency with the alarm system than without, and significantly different patterns of checking for traffic at marked and unmarked crossings. However, unlike in the VR study, no differences were found in approaching time with and without the assistance system. Approaching time was slower at marked crossings. No difference was found with regard to workload, meaning the use of the assistance system did not increase the subjectively perceived workload of participants. Analysis of the acceptance questionnaire showed a positive attachment to the assistance system. However, most reported that they did not experience any advantage from the use of the system, and expressed no intention to buy such a system for themselves.

Peripheral visual perception during natural overground dual-task walking in older and younger adults.

Little is known about the neurophysiological processes underlying visual processing during active behavior and how these change over the life span. This study investigated early (P1) and later (P3) event-related potentials of the electroencephalogram associated with visual perception in older and younger adults while sitting, standing, and walking. While sitting and standing, accurate performance in both groups was not associated with event-related potential characteristics. During walking, in contrast, prolonged latencies and reduced amplitudes of the P1 were related to slower responses and increased misses, respectively. No covariations of behavior and P3 characteristics were observed. However, prolonged P3 latencies with increasing motor task complexity were present for both age groups, and reduced amplitudes while walking were replicated in younger participants. Older participants were more affected by walking in general as reflected in slower walking speeds as well as reduced accuracy and relative P1 amplitudes. These results provide further insights into cognitive-motor interference during natural walking in younger and older adults on early attentional-perceptual processing stages, even for simple additional visual tasks.

Do We Really Need More Stages? Comparing the Effects of Likelihood Alarm Systems and Binary Alarm Systems.

OBJECTIVE: This research investigates the potential behavioral and performance benefits of a four-stage likelihood alarm system (4-LAS) contrasting a 3-LAS, a binary alarm system with a liberal threshold (lib-BAS), and a BAS with a conservative threshold (con-BAS). BACKGROUND: Prior research has shown performance benefits of 3-LASs over conventional lib-BASs due to more distinct response strategies and better discriminating true from false alerts. This effect might be further enhanced using 4-LASs. However, the increase in stages could cause users to reduce cognitive complexity by responding in the same way to the two lower and the two higher stages, thus treating the 4-LAS like a con-BAS. METHOD: All systems were compared using a dual-task paradigm. Response strategies, number of joint human machine (JHM) false alarms (FAs), misses, and sensitivity were regarded. RESULTS: Compared with the lib-BAS, JHM sensitivity only improved with the 4-LAS and the con-BAS. However, the number of JHM misses was lowest for the con-BAS compared with all other systems. CONCLUSION: JHM sensitivity improvements can be achieved by using a 4-LAS, as well as a con-BAS. However, only the latter one may also reduce the number of JHM misses, which is remarkable considering that BASs with conservative thresholds a priori commit more inbuilt misses than other systems. APPLICATION: Results suggest implementing conservative BASs in multi-task working environments to improve JHM sensitivity and reduce the number of JHM misses. When refraining from designing systems which are miss prone, 4-LASs represent a suitable compromise.

Effects of Trust, Self-Confidence, and Feedback on the Use of Decision Automation.

Operators often fail to rely sufficiently on alarm systems. This results in a joint human-machine (JHM) sensitivity below the one of the alarm system. The 'confidence vs. trust hypothesis' assumes the use of the system depends on the weighting of both values. In case of higher confidence, the task is performed manually, if trust is higher, the user relies on the system. Thus, insufficient reliance may be due to operators' overconfidence in their own abilities and/or insufficient trust in the decision automation, but could be mitigated by providing feedback. That was investigated within a signal detection task, supported by a system with either higher sensitivity (HSS) or lower sensitivity (LSS) than the human, while being provided with feedback or not. We expected disuse of the LSS and insufficiently reliance on the HSS, in the condition without feedback. The feedback was expected to increase reliance on the HSS through an increase in trust and/or decreases in confidence, and thus, improve performance. Hypotheses were partly supported. Confidence in manual performance was similar to trust in the HSS even though humans' sensitivity was significantly lower than systems' sensitivity. While confidence had not effect on reliance or JHM sensitivity, trust was found to be positively related with both. We found disuse of the HSS, that could be improved through feedback, increasing also trust and JHM sensitivity. However, contrary to 'confidence vs. trust' expectations, participants were also found to make use of the LSS. This misuse could not be reduced by feedback. Results indicate the use of feedback being beneficial for the overall performance (with HSS only). Findings do not support the idea that misuse or disuse of the system may result from comparison of confidence and trust. We suppose it may rather be the product of users' wrong strategy of function allocation, based on the underlying idea of team work in combination with missing assignment of responsibility. We discuss this alternative explanation.

Conceptualizing Everyday Mobility of Older People as Basis for the Development of a Pedestrian Assistance System.

For older persons, everyday mobility is an important aspect of living an independent and self-determined life. Especially with increasing age most of the everyday ways in urban areas are covered by foot. The more severe is the fact that older pedestrians are among the most vulnerable road users. This is the starting point of the research group FANS aiming for developing a pedestrian assistance system for older road users. Therefore, it is necessary to understand the difficulties older pedestrians encounter. In order to do so, everyday mobility of this group will be conceptualized using the Constraints Approach by Hägerstrand and the Theory of Structuration by Giddens. Currently, two focus groups have been carried out that have been analyzed according to Hägerstand's and Gidden's considerations. Hereinafter, the category system that has been derived from the theoretical considerations will be presented and an outlook will be given.

Supporting attention allocation in multitask environments: effects of likelihood alarm systems on trust, behavior, and performance.

OBJECTIVE: The aim of the current study was to investigate potential benefits of likelihood alarm systems (LASs) over binary alarm systems (BASs) in a multitask environment. BACKGROUND: Several problems are associated with the use of BASs, because most of them generate high numbers of false alarms. Operators lose trust in the systems and ignore alarms or cross-check all of them when other information is available. The first behavior harms safety, whereas the latter one reduces productivity. LASs represent an alternative, which is supposed to improve operators' attention allocation. METHOD: We investigated LASs and BASs in a dual-task paradigm with and without the possibility to cross-check alerts with raw data information. Participants' trust in the system, their behavior, and their performance in the alert and the concurrent task were assessed. RESULTS: Reported trust, compliance with alarms, and performance in the alert and the concurrent task were higher for the LAS than for the BAS. The cross-check option led to an increase in alert task performance for both systems and a decrease in concurrent task performance for the BAS, which did not occur in the LAS condition. CONCLUSION: LASs improve participants' attention allocation between two different tasks and therefore lead to an increase in alert task and concurrent task performance. The performance maximum is achieved when LAS is combined with a cross-check option for validating alerts with additional information. APPLICATION: The use of LASs instead of BASs in safety-related multitask environments has the potential to increase safety and productivity likewise.

Decision-making and response strategies in interaction with alarms: the impact of alarm reliability, availability of alarm validity information and workload.

Responding to alarm systems which usually commit a number of false alarms and/or misses involves decision-making under uncertainty. Four laboratory experiments including a total of 256 participants were conducted to gain comprehensive insight into humans' dealing with this uncertainty. Specifically, it was investigated how responses to alarms/non-alarms are affected by the predictive validities of these events, and to what extent response strategies depend on whether or not the validity of alarms/non-alarms can be cross-checked against other data. Among others, the results suggest that, without cross-check possibility (experiment 1), low levels of predictive validity of alarms ( ≤ 0.5) led most participants to use one of two different strategies which both involved non-responding to a significant number of alarms (cry-wolf effect). Yet, providing access to alarm validity information reduced this effect dramatically (experiment 2). This latter result emerged independent of the effort needed for cross-checkings of alarms (experiment 3), but was affected by the workload imposed by concurrent tasks (experiment 4). Theoretical and practical consequences of these results for decision-making and response selection in interaction with alarm systems, as well as the design of effective alarm systems, are discussed.

Measures of reliance and compliance in aided visual scanning.

OBJECTIVE: We study the dependence or independence of reliance and compliance as two responses to alarms to understand the mechanisms behind these responses. BACKGROUND: Alarms, alerts, and other binary cues affect user behavior in complex ways. The suggestion has been made that there are two different responses to alerts--compliance (the tendency to perform an action cued by the alert) and reliance (the tendency to refrain from actions as long as no alert is issued). The study tests the degree to which these two responses are indeed independent. METHOD: An experiment tested the effects of the positive and negative predictive values of the alerts (PPV and NPV) on measures of compliance and reliance based on cutoff settings, response times, and subjective confidence. RESULTS: For cutoff settings and response times, compliance was unaffected by the irrelevant NPV, whereas reliance depended on the irrelevant PPV. For subjective estimates, there were no significant effects of the irrelevant variables. CONCLUSION: Results suggest that compliance is relatively stable and unaffected by irrelevant information (the NPV), whereas reliance is also affected by the PPV. The results support the notion that reliance and compliance are separate, but related, forms of trust. APPLICATION: False alarm rates, which affect PPV, determine both the response to alerts (compliance) and the tendency to limit precautions when no alert is issued (reliance).