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Biomedical subjects

W Kuhmann

Publications and source records attributed to W Kuhmann.

7 recordsLinked to original sources
PubMed1996

Event-related brain potentials during identification of tachistoscopically presented pictures.

In the present study in 20 healthy subjects, event-related potentials (ERPs) were used to investigate the identification of picture stimuli. Each of 36 landscape pictures and 36 scrambled pictures was presented by a tachistoscope repeatedly until the subject made an identification response. Presentation of one picture was finished after 12 exposures. On the average, landscapes were identified after 5.8 +/- 0.4 exposures; identification responses to scrambles were always wrong and occurred after 11.8 +/- 0.1 exposures. Latencies and amplitude measures were assessed for P2, P3, N400, and the slow wave (SW). Changes in P2 across stimulus presentations did not differ between landscapes and scrambles excluding this component from being indicative for the processing of stimulus meaning. Amplitude of P3 generally declined across presentations, but increased prior to identification for landscape pictures. N400 rapidly declined across presentations of landscapes, but less rapidly for scrambles. The SW increased across stimulus presentations. This increase was more pronounced for landscape than scrambled pictures. The pattern of ERP changes can be interpreted in a framework of a stepwise inhibition of spreading activation within semantic memory with progressing picture identification.

Adult↗
PubMed1995

Standardized task strain and system response times in human-computer interaction.

Involuntary delays in human-computer interaction, for example, system response times (SRTs) can increase stress. In the present study, 40 college-age subjects were randomly divided into an 'incentive' and a 'non-incentive' group'. Subjects performed a computer task with SRTs of 0.5, 1.5, and 4.5s. Physiological, subjective, and performance data were collected during the task. The computer task was designed to individually set difficulty level (i.e., mental strain), thus standardizing the task for all subjects. By using this procedure, changes resulting from SRT duration can be separated from the effects related to task difficulty. The results indicate that both short and long SRTs produced differential psychophysiological changes consistent with different types of stress responses. Short SRTs resulted in higher autonomic and somatic activity, increased positive self-reported emotional states but poorer performance. Long SRTs resulted in increased electrodermal activity, negative self-reported emotional states and better performance.

Adult↗
PubMed1991

[Effect of system-related work interruptions in computer-assisted text processing: a field study].

To validate laboratory research findings on the stress inducing effects of system response time in human-computer interaction, a field study was performed at the central typing office of a bank. Simultaneous subject-oriented and object-oriented measures (questionnaires) of working properties were taken with a relatively high sampling rate over several days in addition to the ordinary business activities. In summary, the negative effects of system response times could also be observed in the real work setting, but were modified by subjective and situational factors which had not been considered in laboratory research yet. The users also avoided situations of temporal uncertainty by adapting their working style to the system. Therefore it is concluded, that the effects of system response time should be interpreted by the concept of user acceptance and not by temporal uncertainty.

Adult↗
PubMed1990

[Effects of waiting times within simple problems: an analogy to waiting times in human-computer interaction].

The impact of forced intra-task waiting periods was evaluated in a laboratory study designed in analogy to forced waiting periods in human-computer interaction. Each task consisted of two lines of grouped capital letters (so-called Sterzinger lines) that had to be processed individually, separated by the experimental waiting period. The final response to both lines was taken after removal of the second line. The experiment was conducted according to a within-subjects design with the order of the two factors "duration" (2 s vs. 8 s) and "variability of the waiting periods" (constant vs. variable) controlled. The dependent variables were performance indices, heart rate, electrodermal activity, and subjective measures of mood and physical complaints. The results showed effects of the duration of waiting periods for the performance and the physiological variables, and effects of the variability factor for the subjective variables. Shorter waiting periods were associated with higher scores of heart rate and skin resistance responses, variable waiting periods seemed to confuse the subjects more than constant ones. The results are discussed with respect to the effects of the two experimental factors. With respect to dialog structures in human-computer interaction, the results lead to the conclusion that response interference could be avoided by giving the user the possibility to immediately input problem solutions. Partial and preliminary inputs should be permanently kept visible during the whole task cycle by the software.

Adult↗
PubMed1989

Experimental investigation of stress-inducing properties of system response times.

System response times are regarded as a major stressor in human-computer interaction. In two earlier studies short (2s) and long (8s) response times were found to have differential effects on psychological, subjective, and performance variables, but results did not favour either response time. Therefore, in another laboratory study with 48 subjects in four independent groups working at a stimulated computer workplace, system response times of 2, 4, 6 and 8s were introduced in the same error detection task as used before, during 3 training and 5 working trials of 20 min each, and the same physiological, subjective and performance measures were obtained. There were no global effects on physiological variables, possibly due to low work load as a result of missing time pressure, but subjective and performance variables clearly favoured the longer system response times. When task periods and response time-periods were analysed separately, a shift of electrodermal activity could be observed from task- to response time-periods during the course of trials in the 8s condition. This did not appear in any other condition, which points to psychophysiological excitement that develops when system response times are too long, thus providing support for the concept of optimal system response times.

Adolescent↗