PATTERNS OF GALVANIC SKIN RESPONSES TO SIGNAL AND NON SIGNAL STIMULI

Two studies investigating the specific features of galvanic skin responses (GSRs) to signal and non-signal stimuli are reported. The results of Exp. I indicate that stimuli which have instructed behavioral associates (signal significance) produce GSRs which are both multiphasic and relatively persistent in nature. Multiple GSRs are produced by the initial presentation of a signal stimulus and the persistence of the overall response appears to have at least a short-term effect on baseline. Exp. II was designed to investigate the possible independence of these two characteristics through the manipulation of response certainty. The results suggest that multiplicity and persistence may be separable features of the response to signal stimuli in which the latter may be a correlate of response novelty.     

CLASSICAL CONDITIONING OF THE GALVANIC SKIN RESPONSE IN IMMOBILIZED CATS

Ten cats were immobilized with Flaxedil and given either paired conditioning trials or unpaired presentations of the CS and UCS in a study of classical GSR conditioning. The paired group received 5 adaptation trials followed by 40 paired tone-shock acquisition trials and 10 extinction trials. A pseudo-conditioning control group received unpaired trials with tone and shock, to control for pseudoconditioning and sensitization. It was found that the group receiving paired conditioning trials responded at a significantly higher magnitude than did control Ss, thus demonstrating classical conditioning in this preparation. Electromyograms were recorded for all Ss during the experimental sessions to monitor skeletal movements. The level of immobilization was such that no movements were seen in response to the CS. Analysis of the baseline skin resistance data revealed no significant differences which could have contributed to group differences in GSR magnitudes. It is concluded that skeletal movement was not a necessary concomitant of classical conditioning of the GSR.     

SKIN POTENTIAL RESPONSES AND THE SPAN OF ATTENTION

Experiment I tested whether an alerting signal would increase the span of visual attention. Female Ss (16) were presented an array of letters exposed for 2 sec by a tachistoscope. Half of the Ss had a series of trials with a loud tone contiguous with the tachistoscope, followed by a series of trials with tachistoscope only. The remaining Ss received a reverse procedure—half the trials with no tone initially, followed by tone. The group receiving only tachistoscope followed by a series of tachistoscope plus tone trials showed a significant improvement in the number of letters correctly reported. Experiment II repeated the above with skin potential (SP) recording throughout the session to test that the tone would generate a momentary state of arousal (an orienting response) and an increase in the span of attention. Tone significantly produced larger positive SP amplitudes and more diphasic SP responses, and increased the number of letters correctly reported. All differences disappeared during the second trial series.     

STATISTICAL DISTRIBUTION OF VOLAR SKIN POTENTIAL LEVEL IN ATTENTION AND THE EFFECTS OF AGE

Skin potential (SP) level was investigated in 58 young (aged 22–53 years) and 64 old (aged 54–85 years) Ss. SP recordings were made during a 15-min interval while Ss were taking part in a watch-keeping task. The Kolmogorov-Smimov test revealed that, while the distribution of SP level in young Ss deviated significantly from normality, the distribution in old Ss was normal. Evidence suggested that age of Ss needs to be taken into account when dealing with distributions of SP level recorded under attentive conditions.     

ADAPTIVE VALUE OF AROUSAL SWEATING AND THE EPIDERMAL MECHANISM RELATED TO SKIN POTENTIAL AND SKIN RESISTANCE

The following five experiments are reported.

• 1 After palmar sweating is abolished by atropine, the skin is easier to drill with a dental burr. This suggests that arousal sweating protects the skin against mechanical injury.
• 2 Intracutaneous injection of acetylcholine or mecholyl at the forearm will produce skin potential (SP) effects of both negative and positive polarity and also a reduction in skin resistance (SR). This suggests that a cholinergic substance is involved in the production of SP and SR.
• 3 Intracutaneous injection of mecholyl at the forearm will either lower or raise the pain threshold to a needle prick. A lowering of the pain threshold was associated with the presence of an SP negative effect and a rise was associated with an SP positive effect. It is concluded that the adaptive value of the cholinergic substance related to SP and SR is to modulate cutaneous sensitivity.
• 4 The pain threshold to an electric shock can be lowered or raised by mecholyl injection. This may show that the pain threshold can be varied by mecholyl injection independently of its effects on sweating.
• 5 Lowering of the electric shock pain threshold at the palm is associated with the appearance of both SP negative and positive responses. This further demonstrates a relation between SP activity and pain sensitivity but indicates that the direction of the change in the pain threshold is not dependent on SP response polarity.

     

THE PERIPHERAL MECHANISM OF THE GALVANIC SKIN RESPONSE

Darrow held that the galvanic skin response (GSR) appears to be a complicated phenomenon because a number of events are sequentially involved. The mechanism resulting in the peripheral components of electrodermal phenomena is not complicated. Following excitation, sympathetic impulses to cutaneous tissues and subsequent release of acetylcholine account for initial negative polarity and resistance changes. When these incoming impulses are sufficiently persistent and strong, and when the cholinergic response of the sweat glands is sufficient, then if temperature and circulatory conditions are favorable, secretion by the sweat glands is initiated. Sweating is the major factor contributing to the positive potential and large drops in skin resistance during excitation, but at low levels of excitation, when skin resistance is high and before sweating has reached a critical level, epidermal activities other than those of the sweat glands may contribute appreciably to negative potential and resistance changes.     

PALMAR SKIN RESISTANCE AND SWEAT-GLAND COUNTS IN DRUG AND NON-DRUG STATES

Propantheline bromide, an anticholinergic blocking agent, was found to nullify all sizable changes in skin resistance. Betazole hydrochloride, a histamine isomer causing flushing of the skin, had no detectable effect on changes in skin resistance. Betazole hydrochloride did decrease the level of skin resistance, and it is possible that increased vasodilatation “pumps” more conductive (saline-like) substances into the skin. These results suggest that relatively rapid changes in skin resistance depend more upon sweat-gland activity than upon changes in the fluid content of the skin, without denying the importance of the latter. It may be that the level of skin resistance at any one time depends upon a combination of sweat-gland and vasomotor activities. Hence, as basal levels of skin resistance decrease, the relative magnitude of changes in skin resistance to stimuli also decreases (law of initial values).     

SELECTIVE HABITUATION OF GALVANIC SKIN RESPONSE COMPONENT OF THE ORIENTATION REACTION TO AN AUDITORY STIMULUS

The prediction from Sokolov's (1960) theory that, following OR habituation, size of OR return is proportional to the amount of difference between the new stimulus and the habituating stimulus was tested using an auditory stimulus varying in frequency and intensity. Five Ss were allocated to each of 16 conditions, three conditions involving changes in frequency, three involving changes in intensity, nine involving changes in both frequency and intensity, with one control condition involving a repetition of the habituating stimulus. Following habituation of the GSR component of the OR to a criterion of response failure for three successive trials, magnitude of GSR under the 16 conditions was measured. Contrary to Sokolov's theory, only increase in intensity had a significantly different effect on OR return. More importantly, it was found that Ss habituating rapidly to the initial stimulus were less likely to show OR return to stimulus change. It was concluded that individual differences in habituation rate may be more important than stimulus difference effects in selective habituation.     

CHARACTERISTICS OF PALMAR SKIN POTENTIAL AND CONDUCTANCE IN RELAXED HUMAN SUBJECTS

An investigation of mechanisms generating palmar skin potential level (SPL) was undertaken from relaxed subjects in a non-arousing environment. In these circumstances it was possible to obtain recordings where there were no skin potential responses (SPRs). At such times of quiescence, SPLs, recorded with 0.5% KCl as the external electrolyte medium, had characteristics which differed from SPLs recorded when there were SPRs. The potentials recorded at the beginning of these periods of quiescence were designated “basal” skin potential levels (BSPLs). BSPLs were demonstrated in other than optimal conditions for achieving basal state, i.e., with non-habituated subjects, and with subjects carrying out an undemanding cognitive task; the relevance of these findings to the use of SPL as an index of arousal in unstimulating conditions is discussed. An interpretation of BSPL phenomena is possible in terms of a relationship between electrode electrolyte and individual values of body fluid potassium.     

SKIN RESISTANCE, SWEAT-GLAND COUNTS, SALIVARY FLOW, AND GASTRIC SECRETION: AGE, RACE, AND SEX DIFFERENCES, ANDINTERCORRELATIONS

Skin resistance, sweat-gland counts, salivary flow, gastric secretion, and pH were measured in volunteers and patients of both sexes, Negroes and Caucasians. Correlational analysis suggested two negatively related clusters: (A) salivary flow, sweat-gland counts, and gastric secretion; and (B) age, skin resistance, and pH. Skin resistance was higher in Negroes than Caucasians, and in females than males, increasing irregularly with age.     

THE INFORMATION CONTENT OF THE RECOVERY LIMB OF THE ELECTRODERMAL RESPONSE

Recent observations suggest that skin conductance or resistance responses manifest, in the shape of the recovery limb, two components, a slow one associated with the negative skin potential response and sweating, and a faster one associated with the positive skin potential response and with the recently reported sweat reabsorption response. Part of the recovery limb has an exponential form, and its recovery rate is interpreted as a measure of the relative participation of these two components. Two simple manual methods, utilizing overlays, allow rapid determination of recovery half-time or time constant. Recovery rate is not determined by amplitude. It can differentiate between spontaneous responses during rest and during a task, between orienting responses to a light flash and responses to the same flash when it takes on signal properties, and between responses to an alerting signal and to an execution signal for a task. Individuals with fast recovery rates during a task also tend to show slower habituation of electrodermal responses. It is concluded that the reabsorption process represents an adaptation for goal-directed behavior.     

HEART RATE, SKIN RESISTANCE, AND REACTION TIME OF MONGOLOID AND NORMAL CHILDREN UNDER BASELINE AND DISTRACTION CONDITIONS

Reaction time, body movement, heart rate, and skin resistance of Mongoloid and “normal” control children were evaluated under baseline and distraction conditions. Relative to controls, Mongoloids demonstrated (1) slower reaction time under both conditions, (2) a reduced skin resistance response and fewer heart rate fluctuations during the baseline period, and (3) fewer skin resistance fluctuations during the distraction condition. Furthermore, skin resistance fluctuations were negatively correlated with reaction time, and heart rate fluctuations, although not significant, were in the same direction. These findings offer some support for the theoretical assertions of Lacey and Lacey (1958) that spontaneous activity is related to motor impulsivity, cortical activity, and general skeletal-motor functions. Body movement was negatively related to these measures of spontaneous activity and thus cannot be invoked as an explanation for the findings.     

PHYSIOLOGICAL AND PERSONALITY CORRELATES OF COMMISSION ERRORS IN AN AUDITORY VIGILANCE TASK

To determine correlates of the tendency to make errors of commission in a vigilance task, 31 Ss worked at a task of listening to recorded digits for 48 min and reported odd-even-odd digit sequences. Reports of “signals” where signals did not actually occur constituted commission errors. While S was engaged in the vigilance task skin conductance was continuously recorded. A measure of extra-version and neuroticism was available for each S. The tendency to make commission errors was associated with decrement in the detection of real signals over time, low GSR amplitude at detection points, and low initial orienting response. Commission errors were positively related to extraversion and unrelated to neuroticism. It was concluded that commission errors are made by Ss who are low in arousal level, subject to vigilance decrement, and likely to score higher on extra-version.