Biomedical subjects

G Vossel

Publications and source records attributed to G Vossel.

At least 19 recordsLinked to original sources

PubMed2001

Psychophysiological differentiation of deception: the effects of electrodermal lability and mode of responding on skin conductance and heart rate.

The differentiation-of-deception paradigm enables the examination of deception as a psychophysiological process by varying, within subjects, two conditions which differ only with respect to honesty and deception. The present experiment assessed the effects of two group factors - electrodermal lability and mode of responding - on the deception phenomenon in a situation with low emotional involvement and mental load. Skin conductance responses, phasic heart rate, self-rated relaxation, calmness, and concentration were the dependent variables. Twenty questions referring to general knowledge were presented on a monitor. The 88 male participants answered half of the questions deceptively and the other half honestly, depending on which of two signals appeared on the screen. Half of the subjects answered verbally and the others by pressing keys. For electrodermal lability and mode of responding, significant main effects on skin conductance and heart rate were obtained. The expected main effect of truthfulness emerged in all variables, without being affected by the group factors. These findings, therefore, extend the generality and robustness of the differentiation-of-deception phenomenon.

Adult↗

PubMed1993

[Methods for quantifying phasic skin conductance amplitudes: threats to validity?].

Two methods of determining the event-related skin conductance response (SCR) amplitude are in common use. In one of these, the difference in conductance between the point of onset and the peak level of a single wave is measured (method 1). The second approach is to determine the difference between two measures, one characterizing the prestimulus level, the other the highest conductance point of the SCR reached within a fixed period following the stimulus (method 2). A problem with quantifying the SCR amplitude occurs when a SCR is elicited before an immediately preceding response has had time to recover, because in this case the two methods lead to quite different values. If the amplitude of each response is measured from its own individual deflection point, the measurable amplitude of the second response will be smaller when it occurs immediately after or in the ascending limb of the first response. The problem is most evident in situations with a high probability of response superimposition, such as when a large number of nonspecific responses occur at the same time as the SCRs. This is found in individuals with a high degree of electrodermal lability. Electrodermal lability refers to a psychophysiological construct that is operationally defined by the frequency of spontaneous electrodermal fluctuations. In the present study, we therefore systematically investigated the effects of the two score methods on SCR amplitude in relation to lability by analyzing electrodermal data from two habituation studies. As expected, several method-specific effects which were related to lability emerged. Results and questions concerning the relevance of the findings are discussed, with special emphasis on the validity of psychophysiological investigations.

Adult↗

PubMed1992

Stimulus rise time, intensity and the elicitation of unconditioned cardiac and electrodermal responses.

In recent discussions on the differentiation of orienting, startle and defense responses, the importance of stimulus rise time for the elicitation of different cardiac response patterns was re-emphasized. Especially, it has been claimed that phasic accelerative heart rate (HR) responses-interpreted as indicators of startle-might not only be evoked by auditory stimuli with instantaneous rise times and high intensities, but also by low to moderate stimulus intensities with sudden onsets. The present study examined this question by manipulating rise time (instantaneous vs. 50 ms) and intensity (60 vs. 95 dB). Subjects (N = 120) were randomly assigned to one of the four independent groups. They performed a habituation experiment in which 12 tones of 1000 Hz with a constant interstimulus interval of 90 s were presented. On trial 13, a change in rise time was introduced by reversing the rise time condition in each group (i.e., from instantaneous to 50 ms and vice versa). Examination of HR changes across 4 poststimulus seconds, of maximal HR deceleration and acceleration, as well as examination of magnitude of skin conductance responses (SCRs) indicated clear intensity effects. Rise time, on the other hand, had no effects on HR and SC that could be interpreted as indicative of startle. Thus, it could neither be observed that instantaneous rise time led to stronger accelerative HR responses nor that the combination of instantaneous rise time and high intensity elicited anything but a dominant accelerative response pattern. These findings were also obtained when the first four trials were analyzed separately. As a consequence of stimulus change, larger SCRs as well as larger decelerative HR responses were observed without, however, being affected by the direction of the change in rise time. In sum, the present study suggests that the role attributed to rise time with respect to eliciting qualitatively different cardiac response patterns has been exaggerated. The consequences for the differentiation of different unconditioned responses are briefly addressed.

Acoustic Stimulation↗

PubMed1991

[Significance of heart rate deceleration in pattern recognition tasks].

As strength of foreperiod heart rate (HR) deceleration in reaction time paradigms with a fixed foreperiod has been discussed in terms of activities related to differences in regulations of attentional processes, the present study was concerned with the question of whether this variable also accounts for the variance in the latency of response in two attention-demanding pattern recognition tasks, one of which involved mental rotation. Subjects were required to determine as quickly and as correctly as possible whether a two-dimensional asymmetrical shape was intrinsically identical to a previously presented visual pattern or not, regardless of its rotational position within the picture plane. The first stimulus was always in normal upright position, whereas the probe stimulus could either be rotated or presented in an upright position. The findings of the study are indicative of a reliable relation between anticipatory HR deceleration and reaction time. It was not restricted to detection and response requirements but also held true in the case of additional mental rotation requirements. Strength of anticipatory HR deceleration is therefore interpreted as an indicator of regulations of attentional processes mustered in order to facilitate or to support stimulus detection and response elicitation as well as to prime or to set up the mental structures required in mental rotation. Additional support for this assumption could be found in the analyses of HR changes at the beginning of the response interval.

Adult↗

PubMed1990

Individual differences in resting heart rate and spontaneous electrodermal activity as predictors of attentional processes: effects on anticipatory heart rate deceleration and task performance.

The present study was concerned with the question of whether tonic resting heart rate (HR) and resting spontaneous electrodermal activity account for the association between anticipatory HR deceleration and task performance in a choice reaction time (RT) task with a fixed foreperiod. The task employed (a varied mapping paradigm) differed from simple RT tasks especially with regard to processing and attention demands. Subjects were required to determine as quickly and accurately as possible whether a 'complex' probe, presented for 80 ms, was identical or not to one of two distinct memory items, presented at the onset of each trial. Reaction times as well as accuracy of responses were determined. Additionally, reaction time and error data were synthesized to obtain a joint measure of response behaviour. The results of the present study were indicative of a reliable anticipatory HR deceleration extended over the last seconds preceding the probe stimulus. In agreement with previous findings, the HR deceleration grew stronger over blocks of trials and was sensitive to detection requirements, i.e. probe complexity. Furthermore, HR deceleration was related to task performance. Subjects with stronger decelerations (below the median on mean deceleration) exhibited a more impulsive (fast-inaccurate) and subjects above the median a more reflective (slow-accurate) response style. The effect was mainly due to a significant difference in RT. Further results indicated that the relationship between anticipatory deceleration and RT performance was especially due to the response behaviour of one group of subjects. Subjects above the median of resting HR and resting spontaneous electrodermal activity behaved in a prominent reflective manner and also displayed the lowest foreperiod deceleration. Results were discussed in terms of differences in the regulation or control of attentional processes.

Adult↗

PubMed1990

Psychometric properties of non-specific electrodermal response frequency for a sample of male students.

In the present study data on the frequency of non-specific electrodermal responses (NSRs) are presented for a large and, with regard to sex, age and educational level, homogeneous sample of male students (n = 590). These data were obtained in 9 independent experiments in which NSRs were recorded under equivalent conditions. NSRs were scored as skin conductance changes greater than 0.02 muSiemens. A recording period of 5 min prior to experimental manipulations was chosen. A systematic comparison between the 9 studies, the distribution of NSRs for the total sample, as well as descriptive data for stabile and labile subgroups are presented. For 213 subjects NSR-frequency was recorded twice, with a retest interval of one day. For these subjects retest analyses and data on the degree of stability of the classification into stabile and labile groups are also presented. In the discussion the necessity to develop standardized scoring criteria for NSRs is emphasized.

Adult↗

PubMed1989

[Anticipatory and event related changes in heart rate as indicators of attention processes].

The present study was concerned with the question of whether phasic event-related heart rate (HR) changes under easy intake conditions account for the association between anticipatory HR deceleration and task performance in a choice reaction time (RT) task with a fixed foreperiod. The task employed differed from simple RT tasks especially with regard to processing and attention demands. Subjects were required to determine as quickly and accurately as possible whether a probe, presented for 80 ms, was identical or not to one of two distinct memory items, presented at the onset of each trial. Reaction times as well as accuracy of responses were determined. The results of the present study were indicative of a reliable anticipatory HR deceleration which was related to latency of responses to the probe stimulus. Subjects with stronger decelerations reacted faster than subjects with diminished or missing decelerations. Furthermore a relation was found between this association and the heart rate changes to repeated presentations of a non-signal auditory stimulus under habituation conditions. Results were discussed in terms of differences in the regulation or control of attentional processes.

Adult↗

PubMed1989

[Critical life change events and disease: approaches, findings and omissions].

One of the most popular approaches concerned with the etiological significance of psychosocial factors is life event research. Life event research concentrates on the relationship between psychosocial events normally occurring in people's lives and the onset of somatic or psychic illnesses. Starting with the approach of Holmes and Rahe a systematic survey about fundamental approaches in life event research is given, guided by the question of the definition of critical events and the question of how to quantify their impact. Based on this survey, representative findings with regard to the relation between life events and illness-related measures are presented, followed by a critical discussion of the relevance of life event research. This discussion concentrates on the problem that life events do not account for a substantial proportion of the variance in the criterion variables. In this context several omissions of previous and recent life event research are noted. It is emphasized that further progress in life event research will only be possible through a substantial conceptual reorientation.

Disease Susceptibility↗

PubMed1988

Electrodermal lability, errors, and reaction times: an examination of the motor impulsivity hypothesis.

Two studies were designed to investigate the effects of electrodermal lability on errors and reaction times (RTs). In Study 1 (n = 56) subjects performed an RT task that in different phases either required only fast responding or additionally discrimination and selection of one of two response alternatives according to specified rules that had to be stored in memory. Results showed that labiles (above the median of resting non-specific electrodermal responses) displayed significantly faster RTs when only speed was required. There were no differences between labiles and stabiles (below the median) in RTs and error rate when discriminations and response selections had to be made. In Study 2 (n = 52) task demands were reduced. Subjects were only required to discriminate between two events and to respond by releasing or retaining one key. Labiles displayed significantly faster RTs. There was furthermore a tendency among labiles to produce fewer False-Responses, i.e. releasing the key when it should be retained. Additional joint analyses of RT and error data revealed a tendency among labiles to perform the task more efficiently. Results are discussed in terms of motor impulsivity and information-processing accounts of electrodermal lability.

Adult↗

PubMed1988