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.     

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.     

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.     

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 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.     

The Electrodermal Orienting Response and Memory: An Analysis of Age Differences in Picture Recall

Young and elderly women were compared on electrodermal measures of the orienting response (OR) to picture stimuli presented during the study phase of a free recall task. Responses were also recorded during a subsequent simple habituation paradigm which was designed to investigate stimulus priming effects. Young subjects recalled more pictures than the elderly and both groups remembered more pictures with common word names than pictures with uncommon verbal labels. Young and older subjects displayed larger skin conductance responses to recalled pictures, especially to recalled uncommon pictures. Older women, however, displayed consistently smaller SCRs than the young. Stimulus priming was observed on the first trial of habituation training where not-recalled pictures evoked smaller SCRs than pictures not shown in the study phase. There were no age differences in habituation across trials. In general, the results indicated that the electrodermal OR is functionally related to recall performance and that the age decrement in recall may be attributed to reduced cognitive effort in the elderly.     

The Variable Response-Stimulus Interval Effect and Sleep Deprivation: An Unexplored Aspect of Psychomotor Vigilance Task Performance

Study Objectives:

The Psychomotor Vigilance Task (PVT) contains variable response-stimulus intervals (RSI). Our goal is to investigate the effect of RSI on performance to determine whether sleep deprivation affects the ability to attend to events across seconds and whether this effect is independent of impairment in sustaining attention across minutes, as measured by time on task.

Design:

A control group following their normal sleep routines and 3 groups exposed to 54 hours of total sleep deprivation performed a 10-minute PVT every 6 hours for 9 total test runs.

Setting:

Sleep deprivation occurred in a sleep laboratory with continuous behavioral monitoring; the control group took the PVT at home.

Subjects:

Eighty-four healthy sleepers (68 sleep deprivation, 16 controls; 22 women; aged 18-35 years).

Measurements and Results:

Across groups, as the RSI increased from 2 to 10 seconds, mean RT was reduced by 69 milliseconds (main effect of RSI, P < 0.001). There was no interaction between the sleep deprivation and RSI effects. As expected, there was a significant interaction of sleep deprivation and time on task for mean RT (P = 0.002). Time on task and RSI effects were independent. Parallel analyses of percentage of lapses and percentage of false starts produced similar results.

Conclusions:

We demonstrate that the cognitive mechanism of attention responsible for response preparation across seconds is distinct from that for maintaining attention to task performance across minutes. Of these, only vigilance across minutes is degraded by sleep deprivation. Theories of sleep deprivation should consider how this pattern of spared and impaired aspects of attention may affect real-world performance.

Citation:

Tucker AM; Basner RC; Stern Y; Rakitin BC. The variable response-stimulus interval effect and sleep deprivation: an unexplored aspect of psychomotor vigilance task performance. SLEEP 2009;32(10):1393-1395.     

Chronic Sleep Reduction: Daytime Vigilance Performance and EEG Measures of Sleepiness, With Particular Reference to "Practice" Effects

Six pairs of young adult 8-hr sleepers were divided equally into two groups, Reduction (R) and Control (C). They adhered to strict bed and arising times for six weeks. Additionally, R subjects reduced their sleep systematically to an average of 6 hrs per night. Following a baseline week, and on a weekly basis, “yoked” pairs of subjects, one from each group, were assessed for daytime sleepiness during prolonged vigilance performance, and by EEG measurement. All-night sleep EEGs were taken on R subjects before and at the end of the reduction. There were no significant differences between the groups for any of the daytime sleepiness measures, but both groups displayed significant “practice” effects over the weeks. R subjects experienced no major difficulties, except for some tiredness around awakening and lunchtime. Overall daytime sleepiness was not increased. Reduction was at the expense of REM and stage 2 sleep, and led to significant declines in sleep onset latency and in stages W + 1 at nighttime. SWS was not affected. This level of reduction in young adults seems to be achieved relatively easily.     

Perceptual factors affecting age-related differences in focused attention: Performance and psychophysiological analyses

In this study, the impact of two perceptual factors, feature similarity and spacing, on age-related differences in performance and psychophysiological measures were investigated within a focused attention paradigm. Young and old subjects performed an Eriksen letter identification task, in which centrally presented targets were flanked by response-compatible or response-incompatible letters. In feature similarity conditions, targets and flankers had a low or high amount of feature overlap. In spacing conditions, flankers were presented at four different lateral positions from the target. In the condition with high feature overlap and shortest target-flanker distance, old subjects showed greater interference by incompatible flankers than young subjects. Feature similarity was of little influence on age-related differences. However, spacing turned out to be of critical importance. Age-related interference effects disappeared when the target-flanker distance increased. This appears to be due to a decrease in response competition.     

Perceptual Preparedness in Man: Brief Forewarning Reduces Electrodermal and Psychophysical Response to Noxious Stimulation

The finding that the skin conductance response (SCR) to a noxious stimulus is reduced by a warning has been attributed to the information the warning conveys or, alternatively, to interference with the SCR to the stimulus by the preceding SCR to the warning. The purpose of this study was to test whether a low-intensity warning stimulus can reduce the SCR to a noxious stimulus independently of SCR interference and produce similar reductions in subjective judgments of stimulus intensity. Eighty subjects were exposed to 30 pairings of a warning with a 98-dB (SPL) noise. The interval between warning and noise was varied (0.5, 1, 3, 11 sec) from one pairing to another. Contrary to the SCR-interference hypothesis, there was a significant linear decrease in the SCR to noise from 0- to 11-sec warning trials. Warnings of 1 sec also significantly reduced magnitude estimations of noise intensity. A control procedure with an innocuous 68-dB tone substituted for the noise indicated that the SCR to innocuous stimuli may also be reduced by warnings, but that the corresponding magnitude estimations are not similarly affected.     

Orienting and Defensive Responding in the Electrodermal System: Palmar-Dorsal Differences and Recovery Rate during Conditioning to Potentially Phobic Stimuli

It was suggested that the effects of fear-relevant pictures as conditioned stimuli (CSs) for electrodermal responses may be explained if it is assumed that they produce conditioned defense responses (DRs), as opposed to the orienting responses (ORs) that are produced by fear-irrelevant stimuli. Some propositions in Edelberg's theory of electrodermal activity were used to differentiate between DRs and ORs in a test of this hypothesis. Groups of subjects were conditioned to fear-relevant (snakes and spiders) or fear-irrelevant (flowers and mushrooms) CSs by means of an aversive (electric shock) or a non-aversive (imperative signal for a reaction time (RT) task) unconditioned stimulus in long interval differential paradigms. The neutral-shock, phobic-RT, and neutral-RT groups showed no palmar-dorsal differences either in magnitude, probability or amplitude, and no conditioning in the recovery rate measure. However, the phobic-shock group showed a peak of dorsal magnitude early in training that subsequently habituated whereas the palmar magnitude data indicated a gradual conditioning effect that lasted throughout the 20 extinction trials. In addition, it showed slower recovery to the reinforced than to the nonreinforced stimulus. These data are taken as support for the hypothesis.     

Individual Differences in Ability to Control Heart Rate: Personality, Strategy, Physiological, and Other Variables

Three experiments (total N = 102) are reported which examined the relationship between individual differences in ability to control heart rate (HR) with feedback and differences in self-reported cognitive strategies, personality variables (locus of control, state and trait anxiety), physiological variables (respiration, somatic activity, basal HR and HR variability, and initial ability to control HR without feedback), and several auxiliary variables (e.g., weight, smoking, gender, exercise, and meditation). Two sets of analyses were performed. In the first set, differences in cognitive strategies and physiological concomitants between HR decrease and HR increase were studied revealing disparate patterns of cognitive strategies and physiological concomitants for the two directions of HR control. In the second set, the group of cognitive, strategy, personality, physiological, and auxiliary variables was searched to determine if any variables were related to individual differences in ability to decrease or increase HR. Cognitive strategies, personality, and auxiliary variables were generally unrelated to ability to control HR in either direction. Use of two cognitive strategies was found to be associated with lack of ability to increase HR, and non-smokers were better able to decrease HR. Strong relationships were found for somatic activity and ability to control HR without feedback, both of which successfully predicted differences in ability to decrease and increase HR with feedback. Implications of these findings for past and future studies of voluntary control of HR are discussed.     

Male mating speed inDrosophila melanogaster: Differences in genetic architecture and in relative performance according to female genotype

From a critical review of the literature on mating speed inDrosophila the importance of fast mating in male fitness is questioned. The genetic architecture of male mating speed (MMS) has been evaluated inD. melanogaster through a populational analysis and a full 5×5 diallel cross between inbred lines. The results emphasize the fundamental role of the female genotype in both the absolute and the relative MMS performances. Somewhat different genetic architectures for MMS are revealed according to the female used in the tests. It is suggested that different parts of the complex genetic system involved in the male's behavioral sexual phenotype are relevant depending on the female's characteristics, thus causing the heterogeneity in the MMS genetic architecture. An overall picture reveals a genetic system characterized by additivity, dominance for fast mating, and no influence of the X chromosome. There results do not support strong natural selection favoring fast mating inDrosophila males.