Electrodermal Lability and Visual Information Processing

Individual differences in electrodermal lability have been related to performance in vigilance and reaction time tasks. The goal of the present study was to employ an "additive factors" approach to identify the stages of information processing that might underlie these effects. Nineteen labile and 17 stabile subjects performed a choice reaction time task in which a visual imperative stimulus was presented under two conditions of intensity (presumed to affect the speed of pre-processing operations) X three conditions of degradation (which influences later encoding processes related to feature extraction). Measures of both reaction time and movement time were obtained. The major findings were: (a) labile subjects had faster reaction times than stabiles, and (b) lability interacted significantly with stimulus degradation. Labiles also tended (p less than .10) to have faster movement times. This pattern indicates that labiles and stabiles differ in the performance of later encoding operations, and possibly in the speed of motor processes as well. However, they do not appear to differ in the early pre-processing of the simple physical attributes of a stimulus.     

Voluntary Heart Rate Control as a Function of Individual Differences in Electrodermal Lability

Twenty-four male subjects were run in a paradigm in which they were first asked to rest for 10 min and then given 20 1-min training trials of analog and digital feedback of their heart rate, with instructions to increase the rate. Subjects were rewarded with 0.2 cents for each interbeat interval that was faster than a designated criterion. Subjects were subdivided into “labile” and “stabile” groups on the basis of frequency of spontaneous skin conductance fluctuations during the baseline period. Mean heart rate for the training trials was compared with the baseline period for the most labile and most stabile subjects. Results indicated that there was a significant treatment effect for stabile subjects only, but not for labile subjects.     

Effects of Electrodermal Lability and Stimulus Significance on Electrodermal Response Amplitude to Stimulus Change

The effects of electrodermal lability and stimulus significance on the amplitude of the skin conductance response (SCR) component of the orienting response (OR) to stimulus change were examined. Subjects were pre-selected in terms of the frequency of nonspecific responses (NSRs) displayed during a period of no stimulation. In Experiment 1 (N = 56), high and low NSR male subjects received 12 presentations of a 5-sec, 1000 Hz tone followed by a test trial on which tone frequency was 500 Hz. Half of the subjects in each NSR group were required to perform a reaction time (RT) response to stimulus offset. Although high NSR groups and RT groups displayed larger test-trial responses than low NSR and no-RT groups respectively, stimulus change alone was sufficient to produce an increase in SCR amplitude. In Experiment 2 (N = 40), high and low NSR male subjects received 12 visually-presented female names, and on trial 13, half the subjects in each NSR group received their own name, while the other half received a neutral male name. High NSR groups and own-name groups displayed larger test-trial responses than low NSR groups and neutral-name groups respectively. However, stimulus change alone was sufficient to produce an increase in SCR amplitude in the high NSR group. The results are interpreted as indicating that stimulus change alone is sufficient to produce an increase in OR amplitude, and that the relationship between stimulus change and stimulus significance is additive rather than multiplicative.     

Electrodermal Lability and Myocardial Reactivity to Stress

The relationship between electrodermal lability and myocardial reactivity to stress was examined in male undergraduates, who were classified as electrodermally labile (n = 19) or stabile (n = 19) based on the frequency of nonspecific skin conductance responses at rest. Heart rate, pre-ejection period, cardiac output, and skin conductance responses were recorded at rest, during task instructions, and during two mental arithmetic tasks that varied in level of difficulty. As predicted, labiles exhibited greater myocardial reactivity to the task instructions and the tasks than did stabiles, with more persistent group differences emerging for pre-ejection period and cardiac output than for heart rate. The group differences did not vary as a function of task difficulty, but did decline over time. These results support a positive relationship between electrodermal lability and beta-adrenergic myocardial reactivity to stress, particularly under conditions of task novelty or uncertainty, and suggest that electrodermal lability is related fundamentally to arousal and reactivity processes.     

Electrodermal Lability and Dichotic Listening

Subjects identified as electrodermal labiles and stabiles on the basis of frequency of nonspecific skin conductance responses during a resting period were presented with a series of auditory stimuli followed by dichotic presentation of different sets of words to each ear with the requirement to report as many words as possible irrespective of ear. Labiles performed better than stabiles on the dichotic listening task and were found to habituate skin conductance response more slowly to both tones and dichotic stimuli, and to show higher skin conductance level during both stimulus series and higher heart rate level during the dichotic series. There were no significant differences between the groups on a measure of EEG alpha activity during either series. The data were consistent with an arousal rather than an attentional interpretation of the labile-stabile difference.     

Effects of Electrodermal Lability and Introversion on Vigilance Decrement

Previous research has suggested that an autonomic nervous system measure, electrodermal lability, and a personality measure, introversion-extraversion, both predict vigilance decrement; mixed results have been obtained in research seeking to correlate these two variables. Two vigilance tasks requiring an easy and a difficult sensory discrimination produced an overall decline in performance over time, but electrodermally labile subjects (those with high frequencies of spontaneous fluctuations of skin conductance and slow habituation to a series of tones) did not show a decline on the difficult task. Signal detection measures of sensitivity and response bias suggest that the Observed differences reflected changes in sensitivity over time and not just differences in criterion for responding. While not correlated with electrodermal lability, introversion was related to a higher initial level of performance on the difficult task. Vigilance tasks requiring rapid but cognitively sample discriminations appear to be more effective in eliciting overall declines in performance. The presence of such a decline may be necessary for observing differential declines in performance between electrodermal labiles and stabiles.     

Effects of Electrodermal Lability and Payoff Instructions on Vigilance Performance

The psychophysiologically based personality dimension of electrodermal lability has been related to vigilance performance. The present study investigated this effect basing lability on spontaneous electrodermal fluctuations and habituation of the electrodermal orienting response, and attempted to modify performance using monetary payoffs. In an auditory vigilance task, detections and sensitivity (d′) declined across blocks, and payoffs influenced detections, commission errors, d′, and response bias in the expected directions. Although there were no main effects for spontaneous lability, habituation labiles had higher log false alarm rates, lower response bias and tended to detect more signals. Using either lability criterion, labiles did not demonstrate a vigilance decrement and were more responsive than stabiles to payoff instructions. Lability based on habituation rate was therefore more clearly related to vigilance performance than lability based on spontaneous fluctuations.     

Electrodermal Lability Predicts Presentation Rate Effects and Stimulant Drug Effects on Paired Associate Learning in Hyperactive Children

Hyperactive children were divided into three groups (electrodermal labiles, electrodermal stabiles, and a medium group which fell in between) on the basis of the frequency of spontaneous electrodermal activity. Subsequent tests on a paired associate learning task revealed that the stabiles and medium groups performed poorly when stimulus-response pairs were presented at a relatively slow rate, while for labiles there was no difference across rates. Treatment with stimulant medication abolished the differences across rates for the stabiles and the medium groups, but led to significantly more learning on the fast rate relative to the slow rate for labiles. While the placebo findings were consistent with a low arousal view of hyperactivity, the drug results suggested that stimulant medication corrects an imbalance in the mechanisms which govern sensitivity to task-related stimulation, but induces an imbalance where none is present on placebo.     

Electrodermal Lability: Individual Differences Affecting Perceptual Speed and Vigilance Performance in 9 to 16 Year-Old Children

Studies on adults have suggested that a deterioration in performance (within session vigilance decrement) on a continuous performance task may be related to individual differences in baseline levels of electrodermal activity (electrodermal lability). This study investigated this relationship in 153 children, aged 9–16 years. A significant vigilance decrement was observed, as indicated by average decreases in perceptual sensitivity (d') over an 11.5-min time period. Although electrodermal labiles were overall more perceptually sensitive than electrodermal stabiles, results did not support the premise that the performance of stabiles decreases over time more than that of labiles. Performance on other cognitive tasks, involving tests of perceptual speed ability, did not appear to be highly related to vigilance performance. However labiles were not only better able to sustain their attention, but also performed better and faster on these cognitive tasks.     

Anticipation and Response Set: Cortical, Cardiac, and Electrodermal Correlates

Three experiments are reported investigating cortical and visceral responding during a twostimulus anticipation paradigm. Male undergraduate volunteers received auditory warning stimuli signalling the presentation of either high or low interest color slides at the end of a 6-sec foreperiod. A between subject factor, reaction time (RT), was included to assess the effects of a motor response on the anticipatory psychophysiology. Subjects performing the reaction time task produced a two component cortical slow potential with both components larger than under no-task conditions. The reaction time procedure also prompted larger visceral responses. The slow cortical response proved most sensitive to the “interest” manipulation when attentional demands were maximized.     

Psychophysiological Activity and the Buildup and Release of Proactive Inhibition in Short-Term Memory

One interpretation of the buildup and release of proactive inhibition (PI) in short-term memory is that the repetition of similar items leads to a decrement in attention which is reinstated via the orienting response (OR) when the novel shift items are presented. In a test of this hypothesis, 72 subjects performed the PI task while skin conductance and heart rate were recorded. Half the subjects received a change in semantic category on a test trial, while the other half did not. In addition, subjects differed with respect to whether the test trial also included a single presentation of a tone to which they had previously habituated, a novel tone not previously encountered, or no tone. In general, the results provided no support for the OR interpretation of PI. While the semantic change led to improved recall, it was not associated with a differential pattern of physiological responding. Furthermore, the interpolated tones resulted in dishabituation of the SCRs for the following memory items, but had no effect on memory performance.     

Effects of Arousal on Habituation of the Electrodermal Orienting Reflex

The effect of level of arousal upon rate of habituation of the electrodermal orienting reflex (OR) was studied by having 20 tone stimuli presented while subjects were either standing or seated. The standing condition was characterized by both a higher heart rate (HR) and a greater frequency of spontaneous skin resistance responses (SRRs). Compared to standing subjects, subjects under the seated condition demonstrated more rapid habituation of the OR as indicated both by a greater decrement in SRR frequency from the first to the last block of trials and by a greater proportion of subjects who failed to respond to any of the last 10 trials. The rate of spontaneous SRRs appeared to parallel these differences in habituation of evoked responses. There were no differences between groups in skin conductance level (SCL), or in either amplitude or frequency of the evoked electrodermal response over the first few stimulus presentations. The results were interpreted as supporting the conclusion that heightened arousal level retards habituation of the OR.     

Disruption and Recovery of the Orienting Response Following Shock or Context Change in Preweanling Rats

Previous research has shown that placement of preweanling rats in an unfamiliar environment inhibits both heart rate and behavioral orienting responses to an auditory stimulus, and that the orienting response gradually reappears during the following 15 min. Four experiments designed to evaluate two potential explanations of this effect were conducted. If the arousal induced by an unfamiliar environment disrupts sensory information processing, so should the arousal induced by mild electric shock. In two experiments, the orienting response was inhibited in proportion to number of shocks received and rate of recovery was comparable to that observed in the unfamiliar environment. New environments also contain many unfamiliar stimuli which may overload the rats' limited information processing capacity. In two experiments a change in environmental stimulation was shown to inhibit the orienting response. Recovery of the orienting response followed the same time course as that seen following shock or placement in an unfamiliar environment. Although the results of this study clearly demonstrate environmental inhibition of the orienting response, they provide little support for either the "arousal" or the "information overload" hypotheses of orienting response inhibition. The implications of these data for current theoretical conceptualizations of the orienting response are discussed.     

Auditory Vigilance Correlates of Electrodermal Response Habituation Speed

The present study was designed to test the hypothesis that individual differences in the speed of habituation of the phasic eleclrodermal response (EDR) reflect characteristic rates of attentional decrement with stimulus repetition. Subjects selected for the extrems of EDR habituation speed to a pure tone were subsequently tested in an auditory vigilance task. Slow habituators showed a high and substained rate of signal detection, while Fast habituatos showed a lower overall rate and a time-on-task decrement. Further analyses employing signal detection theory measures indicated that these detection differences were due to group differences in response criterion levels rather than to differences in the rate of attentional decrement. The implications of this finding for understanding individual differences in EDR habituation speed are discussed.     

Autonomic Correlates of Sensation Seeking and Monoamine Oxidase Activity: Using Confirmatory Factor Analysis on Psychophysiological Data

A negative relationship between platelet monoamine oxidase (MAO) activity and Sensation Seeking (SS) has been reported in several studies. This study evaluates the possible contribution of autonomic nervous system (ANS) activity to this relationship. Additionally, confirmatory factor analysis was used to create models of ANS concepts from a larger number of psychophysiological variables. Skin conductance (SC) and heart rate (HR) were recorded from 46 men and 49 women during a two-session protocol that included rest periods, a balloon stress, a series of tones, and two tasks: two-flash threshold and tachistoscopic recognition. Results showed that the best-fitting models for both rest and task periods included concepts of SC base levels (“arousal”), SC lability, and HR, and were quite similar for men and women. MAO activity correlated positively with SC concepts, most strongly for women. Women showed negative relationships between sensation seeking and both SC arousal and HR concepts. In contrast, men showed evidence of positive relationships between SC concepts and an active life style. The sex differences and response specificity in these relationships make it unlikely that ANS activity mediates the negative MAO-SS relationship.     

Effects of Momentary Changes in Arousal on Discriminative Autonomic Classical Conditioning

Relative to an intermediate arousal level, effects of stimulus-controlled increases and decreases in arousal were examined during discriminative autonomic conditioning. After matching subjects to psychophysiologically-indexed arousal criteria, three experimental and two control groups of 14 persons each were formed. Experimental groups received both high arousal training consisting of aversive conditioning with a discrete stimulus and low arousal training involving paired presentations of muscle biofeedback relaxation and a different cue. Formation of stimulus controlled arousal responses was assessed using heart rate, muscle, and electrodermal criteria. During discriminative conditioning, one experimental group received all conditioned stimuli compounded with high arousal cues, while another group received conditioned stimuli/low arousal cue compounds. The third experimental group received conditioned stimuli/neutral cue compounds. Electrodermal and digital pulse volume conditioning data indicated significantly greater conditioning associated with neutral cue manipulations. High arousal cue compounds resulted in conditioning superior to that displayed by low arousal cue compounds. Control groups data suggested that results were not due to simple transfer or physical cue properties alone.     

Stimulus Repetition, Change, and Assessments of Sensitivities of and Relationships Among an Electrodermal and Two Plethysmographic Components of the Orienting Reaction

Twenty Ss were presented with 15 300-msec tones (for half the Ss) or lights (for the remaining Ss) followed by a change trial to the other modality. There was highly reliable habituation in the electrodermal skin resistance response (SRR) and the plethysmographic pulse volume (PV), but no clear habituation in the plethysmographic blood volume (BV). Change produced reliable increases in all three orienting-reaction (OR) components. Application of signal-detection methods showed SRR to be a more sensitive index of both initial OR and OR to change than either PV or BV, which were not different. Neither PV nor BV were correlated with SRR, but the BV-PV correlations were significant, and, when corrected for attenuation, approximated +.75. The problem of why the plethysmographic OR components sometimes habituate to stimulus repetition, and sometimes do not, was discussed, but it was concluded that while some possible explanations have been eliminated by the present results, the problem itself still awaits solution and poses a challenge to psychophysiologists.     

Electrodermal Discrimination of Familiar and Unfamiliar Faces: A Methodology

A study is reported which establishes a methodology for investigating the hypothesis that prosopagnosic patients, who have lost the ability to recognize faces, may nonetheless demonstrate electrodermal discrimination of familiar versus unfamiliar facial stimuli. Skin conductance response (SCR) data were recorded while neurologically-intact, college-aged subjects viewed slides of 8 famous, highly familiar faces and 42 unfamiliar faces. The results showed that the familiar faces elicited, on the average, much larger SCRs than the unfamiliar faces. In addition, a second group of subjects rated the familiar faces as more “significant” than the unfamiliar ones, and it is concluded that highly familiar faces are potential signal stimuli. Also, because the paradigm involves few instructions and no overt behavioral response by the subject, this methodology could be readily adapted to investigations of prosopagnosic and other brain-damaged populations in which there is severe amnesia, aphasia, or apraxia.     

Cardiovascular and Skin Conductance Correlates of a Fixed-Foreperiod Reaction Time Task in Retarded and Nonretarded Youth

Changes in heart rate (HR), digital and cephalic pulse amplitude, and skin conductance were studied during a fixed-foreperiod reaction time (RT) task. Mentally retarded adolescents with a mean mental age of 9 yrs, 10 mos were compared with two nonretarded groups matched on mental age (MA) and chronological age (CA), respectively. AH subjects received 20 RT trials with distractors (music) during the 4-sec preparatory interval (PI) and 20 trials without music in a counterbalanced design. The warning signal was a 1 sec light presentation and the reaction signal was an 82 dB tone. Retarded subjects had longer and more variable RTs than the controls. Retarded subjects had smaller HR accelerations and decelerations during the PI than the CA group but not less than the MA group. Further, the retarded group had a marginally lower tonic skin conductance level, smaller skin conductance responses, and smaller constrictions in cephalic pulse amplitude than the CA controls. The results are discussed in terms of attentional and arousal deficits in retarded persons. Some comments are focused on the developmental findings (MA vs CA groups) and on the discrepancies among the skin conductance and cardiovascular measures.     

Prior Activity as a Determinant of Electrodermal Recovery Rate

This study attempts to assess Bundy's 1974 report that electrodermal recovery rate (ERR) can be accurately predicted by a variable, X, based on the recency and amplitude of prior activity. Five different types of assessment were made with the following results. (1) ERR was significantly related to X in two paradigms which avoided the temporal constraints of Bundy's experiment. (2) ERR of responses to repeated reaction time stimuli could be altered by controlling the magnitude of X. (3) A change in stimulus from a reaction time signal to a loud noise failed to change ERR when the value for X was held constant and when response amplitude was treated as a covariate. (4) The rank order of ERRs for reaction time signals and for loud sounds could be reversed by controlling the magnitude of X. (5) Differences in ERR associated with a cold pressor exposure and a mirror tracing task were reevaluated taking into account prior activity. Analysis of covariance with Bundy's X as the covariate failed to erase the difference. However, with a new covariate, namely the number of electrodermal responses in the 15 sec before the measured response, the difference in ERR became nonsignificant. In agreement with Bundy, prior activity appears to represent a major determinant of recovery rate. It is suggested that for those studies reporting ERR differences, attention should be focused on the biobehavioral implications of the likely differences in prior activity.