David A.T. Siddle

Cardiac and forearm plethysmographic responses to high intensity auditory stimulation

This paper reports an investigation of forearm blood flow and cardiac responses to high intensity auditory stimulation. Blood was assessed in terms of forearm girth (FG) using a strain gauge, and since this technique had not been used previously, a preliminary study was conducted to validate the measure. In Experiment 1 (N = 24), subjects performed either a fast- or slow-paced mental arithmetic task. The data indicated that the strain gauge technique differentiated periods of rest from arithmetic stress and produced results comparable with those obtained using limb volume plethysmography. In Experiment 2 (N = 24), subjects received eight presentations of either a 60 dB or a 110 dB white noise stimulus at randomly ordered intervals of 35, 40, 45 and 50 sec; stimulus rise time was 50 msec and the duration 1 sec. Both groups displayed short-latency (i.e. within 10 beats poststimulus) cardiac accelerative responses which habituated over trials. In addition, the 110dB group displayed a long-latency (19.9 sec) accelerative response of approximately 25 beats per min and this was accompanied by an increase in FG. These responses occurred only following the first stimulus presentation, and analysis of the EKG T-wave amplitude suggested that the cardiac response was mediated sympathetically. These results are discussed in terms of conceptions of the startle and defence responses in man and the fight/flight reaction in animals.

Insensitivity to stimulus validity in human pavlovian conditioning

Four experiments investigated the role of information value, or stimulus validity, in human electrodermal conditioning. Conditioned stimuli (CSs) were long, variable duration (10-50-sec) slides or sounds, the unconditioned stimulus (US) was shock, and the primary measures were change in tonic skin conductance level and self-report expectancy of shock. In Experiment 1 electrodermal responding to a target stimulus was marginally lower in a blocking group than in a superconditioning group. This difference failed to occur in Experiment 2, despite increased sensitivity of the electrodermal measure. Explicit instructions to pay attention to the relationship between each stimulus and shock improved learning, but did not lead to group differences (Experiment 3). In Experiment 4 expectancy ratings in a blocking group were lower than in an overshadowing group, but no electrodermal differences occurred. The results were interpreted in terms of non-additive learning processes such as occasion-setting, in addition to a general lack of transfer of learning about a stimulus from one context to another (element to compound or vice versa). It was suggested that sensitivity to stimulus validity might be observed if conditioning were embedded in a causally familiar task, as in contingency judgement research.

Effects of stimulus omission and stimulus change on dishabituation of the skin conductance response.

Three experiments examined the effects of stimulus omission and stimulus change on dishabituation of the skin conductance response. In all experiments, subjects received 17 tone-light or light-tone (S1-S2) pairings, and the primary manipulations were omission of and change in S2 on Trial 16. Responses to S1 and S2 on Trial 17 constituted the data of primary interest. Experiment 1 (N = 72) demonstrated that omission of an expected stimulus was more effective in producing dishabituation than was presentation of an unexpected but not experimentally novel stimulus. Experiment 2 (N = 60) indicated that both omission of an expected stimulus and presentation of an unexpected and experimentally novel stimulus produced dishabituation. Experiment 3 (N = 72) revealed that both the omission and the miscuing of 52 produced reliable dishabituation. The results are interpreted as indicating the importance of a comparison between current input and the stored representation of previous stimulation in the development of habituation.

Reliability of electrodermal habituation measures under two conditions of stimulus intensity

Abstract The present study investigated test-retest reliability of habituation of the evoked skin conductance response. Subjects received 20 presentations of a 1000-Hz, 3-sec tone at the same time of day on two separate occasions, separated by an interval of 97–160 days. Thirteen subjects received stimuli of 90 dB, while for 24 subjects, stimulus intensity was 70 dB. Interstimulus interval was 21 sec for both groups. Both absolute rate of habituation and trials to criterion displayed moderate reliability, and the relationships between habituation measures and other aspects of electrodermal activity were in agreement with previous findings.

Effects of conditioned stimulus preexposure on human electrodermal conditioning

Two experiments investigated the effects of conditioned stimulus (CS) preexposure on Pavlovian differential conditioning and extinction of the skin conductance response. In both experiments, half the subjects were exposed to 20 presentations each of the CS+ and CS-, and the other half were exposed to control stimuli. CS duration was 8 sec. The unconditioned stimulus in Experiment 1 (N = 48) was a 1000 Hz tone of 80 dB which signalled a reaction time requirement, and in Experiment 2 (N = 48), it was a 1 sec burst of white noise at 105 dB. The results of Experiment 1 indicated that no-preexposure groups displayed more CS+/CS- differentiation than preexposure groups during acquisition and more resistance to extinction, at least for the first interval anticipatory response. In addition, the results of Experiment 2 indicated that no-preexposure groups displayed more differentiation than preexposure groups in terms of the second interval anticipatory response. These data constitute a demonstration of the latent inhibition effect with human subjects, and imply that there is an intrinsic relationship between the orienting response and the conditioning process.

Effects of question type and experimenter position on bilateral differences in electrodermal activity and conjugate lateral eye movements.

Abstract 28 dextral males participated in a within-subjects experiment which tasted for the effects of question type (verbal versus spatial) and experimenter-position (in front of or behind the subject) on direction of conjugate lateral eye movements (LEMs) and bilateral differences in skin conductance responses (SCRs). Question dependent asymmetries were observed for LEM direction but not for SCR magnitude. Experimenter-position had no significant effect. The results for LEM direction are consistent with the hypothesis linking eye movements to the left or right with activation of the cerebral hemisphere contralateral to the direction of gaze. The results for SCR magnitude, given certain assumptions, can be reconciled with a hemispheric model of contralateral excitatory control of that system.

EFFECTS OF LENGTH OF TRAINING AND AMOUNT OF TONE INTENSITY CHANGE ON AMPLITUDE OF AUTONOMIC COMPONENTS OF THE ORIENTING RESPONSE

Abstract The present study investigated amplitude of the skin conductance response (SCR), heart rate response (HRR), and digital pulse amplitude (DPA) response components of the orienting response to a change in tone intensity following habituation training. Experimental subjects received either 5 or 20 presentations of a 1000 Hz, 70 dB training stimulus of 3 sec duration followed by presentation of a test stimulus. Half of these subjects received a test stimulus of 63 dB (decrease of 7 dB), while for the other half, the test stimulus was a 56 dB (decrease of 14 dB) tone. Two independent control groups received 6 and 21 presentations of the training stimulus respectively, resulting in a 3 × 2 factorial design (N = 90). The results indicated that test trial SCR amplitude was significantly larger in the 14 dB change groups than in either the 7 dB change groups or the control groups. The 7 dB change groups did not differ significantly from the control groups in terms of test trial SCR amplitude. Experimental...

Effects of fear-relevance on electrodermal safety signal learning.

Safety signal learning in human subjects was investigated using a conditioned inhibition procedure with a shock unconditioned stimulus (US). The conditioned stimulus (CS) duration, and thus the CS-US interval, varied randomly from 20 to 50 s. Conditioning was assessed by change in tonic skin conductance level (SCL). Experiment 1 demonstrated reliable learning of a conditioned inhibition (A+/AB-) discrimination, in terms of both self-reported shock expectancy and change in SCL, in subjects who were able to report correctly the stimulus contingency. There was, however, no evidence of transfer of inhibitory properties from the safety signal B to a separately trained excitor. Experiment 2 compared two groups in which the safety signal was either fear-relevant (picture of snake or spider) or fear-irrelevant (flower or mushroom). As in previous research, there was no effect of fear-relevance on safety-signal learning. The results are discussed in terms of preparedness theory and excitatory conditioning with fear-relevant stimuli.

Effects of stimulus content and postacquisition devaluation of the unconditioned stimulus on retention of human electrodermal conditioning and relational learning

Abstract The present experiment (W=72) employed a differential conditioning procedure to investigate the effects of fear-relevance of the conditioned stimulus (CS) and postacquisition exposure to the unconditioned stimulus (US) on the retention of human autonomic conditioning and relational learning. The CSs were pictures of snakes and spiders (fear-relevant) for half the subjects, and pictures of flowers and mushrooms (fear-irrelevant) for the other half. A delay conditioning procedure was employed with a GS-US onset interval of 8 sec. Following the acquisition phase, one group was exposed to 30 presentations of US-alone, another was exposed to 30 presentations of white noise, and a third group received no stimulation. The dependent variables were the skin conductance response (SCR) and a continuous measure of US expectancy. The results indicated that fear-relevant CSs elicited larger responses during the adaptation phase and resulted in greater first- and second-interval SCR conditioning than did fear-i...

The effects of anticipated information on skin conductance and cardiac activity

This experiment examined electrodermal and cardiac activity within a two-stimulus anticipation paradigm. A warning stimulus informed subjects (N = 24) whether an imperative stimulus to follow would contain two or four letters (low or high information conditions) and whether this stimulus would be presented for 60 or 75 msec (short or long duration). The subjects task was to identify as many of the letters in the imperative stimulus as possible. Although the amount of information conveyed by the warning stimulus was identical throughout the experiment (2 bits), skin conductance responses during the warning stimulus-imperative stimulus interval were larger prior to the high information imperative stimulus than prior to the low. Cardiac activity was not affected by the experimental manipulations. The implications of these findings for theories of the orienting response are discussed, particularly with reference to the view that orienting reflects an activation of the information processing system.