Habituation of the Orienting Response in Sleep

This experiment was designed with stimulus parameters deliberately chosen to maximize the probability of observing habituation of the orienting response (OR) in sleep: weak stimulus, short interstimulas interval. with test for both dishabituation and spontaneous recovery, Habituation of finger plethysmograph. heart rate, skin potential. and skin resistance responses was studied in delta sleep and RKM sleep in 46 male undergraduate volunteers. There was significant habituation of both finger plethysmograph and heart rate responses in both delta and REM sleep, as well as dishabituation and spontaneous recovery. None of these effects was observed in the electrodermal measures. Results were compared with other studies of habituation of the OR in sleep, as well as theories of habituation. The authors do not interpret the results as demonstrating learning during steep.     

Habituation of The Orienting Response to Complex Sequences of Stimuli

The present paper investigates habituation of the electrodermal component of the orienting response to complex sequences of stimuli—i.e. sequences of at least two different recurring stimuli. From the simple habituation curve to one stimulus, three alternative models are suggested to predict the response to that same stimulus in a given trial of the complex sequence. The study was carried out in two stages. In Experiment 1 simple habituation curves were constructed for two types of stimuli (chosen and non-chosen). The results of this experiment provided two negative exponential functions fitted to the data of 101 subjects. Experiments 2 and 3 were designed to compare the models and used complex sequences of chosen and non-chosen stimuli in different mixtures. The prediction of each model was correlated with the actual data of 120 subjects in Experiment 2 and 160 subjects in Experiment 3. The two experiments produced a similar picture regarding the relative validities of the three models. The two models that assume independent habituation processes of the two stimuli comprising the sequence fitted the data better than a model that assumes complete generalization of habituation. The results were discussed within the framework of Sokolov's theory. Theoretical and methodological implications of the models were mentioned, and several suggestions for further research and formulation of more complex models were proposed.     

Amplitude and Habituation of the Orienting Reflex as a Function of Stimulus Intensity

Two within-S experiments involving 20 Ss each and one between-S experiment employing 100 Ss were performed to examine effects of stimulus intensity on orienting response amplitude and habituation. Five intensities of a 1000 Hz tone were presented, ranging from 0 to 40 dB in Experiment I and from 0 to 80 dB in Experiments II and III. Response measures were skin conductance response (SCR) and heart rate (HR). Skin conductance response amplitude increased monotonically with stimulus intensity while HR deceleration was a generally decreasing function which tended to decrease, increase, and finally decrease again as intensity increased. Not only was deceleration greatest at 0 dB but it was more resistant to habituation. Several intensities of test stimulation were presented after habituating stimuli in the between-S experiment. Skin conductance response to test stimuli was facilitated by habituation at 0 dB and depressed by habituation at 80 dB. The results suggest a direct relationship between stimulus intensity and development of habituation.     

Effects of the Range of Stimulus-Variation Upon Habituation of the Orienting Response

The effects of the range of stimulus-variation upon the habitation and return of the skin resistance response (SRR) component of the orienting response (OR) were investigated in three experiments using human subjects. In Experiment I the habituation and return of the OR were studied in two groups with a wide (Group-W) und a narrow (Group-N) range of stimulus-variation. Habituation in the two groups did not differ, but a differential level of return of the OR to a novel stimulus was observed. In Experiment II the difference in the range was made large and a group presented with a constant stimulus (Group-C) was added. Again Group-W and -N habituated in the same way as Group-C. In Experiment III the upper end stimulus of each group was set at the same intensity. The differential return of the OR disappeared, and as before a differential habituation could not he detected between Groups-W and -N. These findings were discussed in reference to Sokolov's neuronal model of the OR.     

Effects of an Attention-Demanding Task on Amplitude and Habituation of the Electrodermal Orienting Response

Two experiments were designed to investigate the effects of performance of a central task on habituation of the skin conductance response to task-irrelevant stimuli. In Experiment 1 (N=48), subjects performed a visual monitoring task in which stimuli were presented at either 800 or 1000 msec. Half the subjects in each group received task-irrelevant tones of 70dB while the other half did not. The results indicated that task-irrelevant tones elicited responses that were larger than those associated with performance of the monitoring task itself, and that responses were larger and habituation slower in the high demand (800 msec) condition than in the low (1000 msec). In order to distinguish between different explanations of these results, Experiment 2 (N=64) employed the same central task and utilized an unexpected change in the pitch of the task-irrelevant stimulus after 20 habituation trials. The results indicated that although habituation was again slower in the high demand condition than in the low, change trial responsiveness was less in the former than in the latter. The results are discussed in terms of arousal and information-processing accounts of habituation.     

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.     

Habituation of the Orienting Response: A Gating Mechanism Subserving Selective Attention

The purpose of this investigation was to determine whether prior habituation of the phasic orienting response (OR) to stimuli which were later to be used as distractors in an attention demanding task, would improve task performance and reduce OR frequency to distractors during the task. The task was the solution of mathematical problems from immediate memory, and the distractors were random numbers and mathematical signs. Subjects were sequentially assigned to one of four conditions: 1) 15 presentations of distractors, problems with distractors; 2) 15 presentations of a tone, problems with distractors; 3) problems with distractors; and 4) 15 presentations of distractors or tone, problems without distractors. Results clearly indicated that prior habituation of the phasic OR to the distractors improved performance relative to no prior habituation or to prior habituation to a tone. There was also evidence of decreased OR activity during problem solving in the prior habituation group relative to the tone habituation and no habituation groups. The data supported an hypothesis that selective attention consists of at least two processes: 1) sensitization of phasic and tonic ORs to salient stimuli, and 2) habituation of phasic and tonic ORs to irrelevant stimuli.     

Scoring Criteria for Response Latency and Habituation in Electrodermal Research: A Study in the Context of the Orienting Response

Levinson and Edelberg's (1985) recent critique of scoring criteria for electrodermal studies pointed to the need to reduce the latency range used to define the electrodermal response. The present study examined the impact of such a narrowing of the latency window upon habituation and instructional effects in studies of the orienting response to low intensity innocuous stimuli. The first experiment found only a small effect of halving the latency window upon habituation to neutral stimuli, apparent as a strengthening of trends over trials. A second experiment showed somewhat larger effects with significant stimuli, apparent as slightly modified trial and group effects. These data support the view that nothing is to be lost by moving to a narrower latency range to define the electrodermal orienting response to stimulus presentation, and suggest that the advantages of such a change will become increasingly important as nonspecific electrodermal fluctuations increase with increasing electrodermal arousal. An analysis of habituation criteria within this context suggested that the choice of two rather than three no-response trials to define habituation adds to the benefits obtained by the selection of a narrow latency window to define the response.     

An Empirical Test of Sokolov''s Entropy Model of the Orienting Response

Several hypotheses, most of them deduced from Sokolov's entropy model of the Orienting Response (OR), were tested. The Galvanic Skin Response (GSR) served as the indicator of the OR. Printed language, analyzed with regard to the information content in bits, was used as stimulus material. Forty-eight female students served as subjects. The results indicate: (1) that the uncertainty of a situation does not determine the strength of the OR, (2) that the strength of the OR depends on the information carried by an event, and (3) that the processing of this information, as indicated by the OR, may be delayed by one or more events in a serial application. For tonic level over a series of events no trend could be found.     

Delayed Habituation of the Electrodermal Orienting Response as a Function of Increased Level of Arousal

Level of arousal was manipulated by having subjects perform arithmetic tasks during a habituation procedure, which consisted of 55 presentations or a 1000 Hz. 80 dB tone. For one group a threat of shock was added to the task performance in order to include aspects of stress in the arousal manipulation. These two groups were compared with a group who heard the same stimuli but were simply instructed to relax. The three groups differed in level of arousal according to KEG signs of drowsiness, skin conductance level, and frequency of spontaneous skin conductance responses, All three groups differed from each other in number of trials to habituation criterion for skin conductance responses to stimuli. Since the delay of habituation was seen tin- both the Task group and the Shock-threat group, it was concluded that the effect was not bound to aspects of stress but was a general effect of increased arousal. For vasomotor responses an analysis in terms of habituation was difficult to apply because the two high arousal groups were very unresponsive from the beginning.     

Stimulus Omission and the Orienting Response

Omission of a stimulus, after its regular presentation has resulted in response habituation, was observed by Sokolov to elicit an orienting response. Although noted some years ago to be crucial in differentiating competing theories of response habituation, strong support for the existence of this phenomenon is lacking in the literature. The present study examined the magnitude of the orienting response to stimulus omission as a function of sex, initial response magnitude, and habituation rate. Response magnitude was significantly greater following stimulus omission than in a control period, and this difference was independent of sex, initial response magnitude, and habituation rate. However, only 22 of the 48 subjects showed greater activity following stimulus omission than in the control period, and 9 showed the reverse. While confirming the existence of the missing-stimulus effect, these results indicate that the phenomenon is relatively fragile when compared with expectations from a reflexive, involuntary stimulus-comparator process as proposed by Sokolov.     

Cardiac Orienting to Pulsed and Continuous Auditory Stimulation: A Developmental Study

Pulsed presentations of auditory stimulation have been shown to be particularly effective in eliciting cardiac deceleration (orienting) during earliest infancy. In the present study the processing of pulsed as compared to continuous stimulation was studied developmentally for two infant age groups (13–18 and 26–35 weeks) and one adult group. Ten habituation trials of either a pulsed or a continuous 10-sec tone were followed by 2 dishabituation trials, in which the temporal pattern (continuous vs pulsed) was shifted. The dishabituation data showed that the two kinds of stimulation were discriminated, but the only finding of differential processing relating to the relevance of pulsed stimulation for younger infants was a tendency for infant subjects, unlike adults, to show prolonged orienting to initial presentations of the pulsed tone. For rate of habituation there were no differential effects. Only in the adult group was the response during dishabituation influenced by the direction of change of temporal pattern. Orienting to stimulus offset was observed on initial presentations of the continuous stimulus for the older infant group.     

The Sleeping Rat Shows Signs of Orienting Response to Neutral Stimuli

Cortical arousal, cardiac response, and body movement to auditory stimuli were studied during slow wave sleep (SWS) of the rat. Rats were exposed to sequences of 10 tone pulses of a frequency of 16 kHz, a sound pressure level of 60dB, and n duration of 2 s (Experiment I) or 10 s (Experiment II). Repeated stimulus presentations permitted the evaluation of short-term habitation. Similar results were found in both experiments, i.e. habitation of the cortical arousal response and of the phasic cardiac deceleration to stimulus onset and offset. With repeated presentations, cardiac acceleration showed a less regular course than cardiac deceleration and cortical arousal. Subsequently presented tone pulses of 80dB did not result in a recovery of the habituated response. Cardiac deceleration and cortical arousal on the one hand, and cardiac acceleration and motor activity on the other hand, were strongly correlated. The results are compared with human studies.     

Effects of a Change in Tone Frequency on the Habituated Orienting Response of the Sleeping Rat

EEG arousal and heart rate responses to change in tone frequency following habituation training were studied during slow wave sleep in the rat. Rats were exposed to sequences of 12 tone pulses. Habituation stimuli (trials 1-7) had a frequency of 16 kHz. The frequency of the following (test) trials was changed to either 5, 12, 14, 22, or 40 kHz. Hearing level was held constant for all frequencies. Test trials were repeated five times to study rehabituation. The results indicate that heart rate deceleration is an indicator of the orienting reflex and its magnitude is a positive function of the amount of frequency change of the stimulus. Large frequency changes in either direction relative to the habituation frequency lead to re-evocation of the habituated EEG arousal and heart rate deceleration, with subsequent rehabituation. Small tone-frequency changes do not result in EEG arousal or heart rate deceleration responses that differ from the responses to the habituated frequency. Heart rate acceleration shows neither short-term habituation nor significant reaction to any of the test frequencies.     

Habituation During Sleep

In some recent reports, authors have found no evidence for habituation during sleep, and have concluded that habituation and sleep are incompatible. This finding was tested using skin potential, heart rate, and EEG responses to a 70 dB, 1 sec, 1000 Hz tone, in sleep stages 2, 4, and REM, with daytime controls. Interstimulus intervals used ranged from 10 to 30 sec. Autonomic responses analyzed separately for each series of stimuli showed significant habituation, except for heart rate responses in REM and in the daytime (drowsy) controls. EEG responses also demonstrated habituation. An interstimulus interval effect was found with EEG K-complexes, habituation occurring more slowly or not at all with the longer, irregular interstimulus intervals. It is suggested that previous failure to detect habituation has been due to a technique of averaging responses over hourly periods and/or the use of long irregular interstimulus intervals. It is concluded that habituation is indeed possible in human sleep if stimulus intervals are not long.     

The Effects of Cognitive Set on the Electrodermal Orienting Response

Two experiments were designed to examine the effects of cognitive set acquired during problem solving upon the orienting skin conductance response (SCR) to a tone and its omission. Forty-two female college students were instructed to press a key when they had found out the rule set up between the presentation of a tone and a particular digit associated with the tone. In Experiment 1, the tones were presented at every third ‘0’position, at first. After this rule was discovered, in the first group, the tone-presentation was altered to the every third ‘7’position (Tone 0–7 Group: n=7). In the second group, the tones were not further presented after the rule was discovered (Tone 0-No Tone Group: n=9). In the third group, the tones were continuously presented even after the subjects had found the rule (Tone 0–0 Group: n=9). Then, in the Tone 0–7 and Tone 0–0 Groups one no-tone trial was given. The results showed that the change of tone-rule in the Tone 0–7 Group and the tone-omission did not evoke an orienting response. In Experiment 2, the instructions were improved so that the subjects would maintain a cognitive set to detect a possible future change in the rule. Two groups, the Tone 0–7 (n=8) and Tone 0–0 (n=9) Groups, underwent the same procedure as in Experiment 1. It was shown that the change of tone-rule in the Tone 0–7 Group and the tone-omission in the Tone 0–0 Group evoked the orienting response.     

Orienting, Habituation, and Short-Term Memory

Two experiments investigated the relationship between orienting activity and proactive inhibition in the Brown-Peterson short-term memory paradigm. In both experiments, different groups of 4 words were presented on each of 6 trials, and recall was tested on each trial following a rehearsal-prevention period. Electrodermal activity was monitored throughout. The taxonomic category of words was the same throughout Experiment 1 (N = 96) for control groups, whereas for experimental groups, trial 5 consisted of words from a different category. In Experiment 2 (N = 96), taxonomic category was the same on all trials for all groups. However, intertrial intervals (ITIs) were either short or long, and for experimental groups, the trial 5–trial 6 ITI was either shortened or lengthened. The results of both experiments indicated that decline in recall performance across trials 1–5 was accompanied by a decrease in skin conductance response (SCR) magnitude. The change in taxonomic category in Experiment 1 produced both improved recall and increased SCR magnitude. The results of Experiment 2 indicated that both recall performance and SCR magnitude declined more slowly with long than with short ITIs. Moreover, an increase in ITI produced improved recall and increased SCR magnitude. However, although a decrease in ITI produced a decrement in recall performance, it had no effect on SCR magnitude. The results are discussed in terms of current theories of habituation and proactive inhibition in short-term memory.     

Repeated Habituation and Overhabituation of the Orienting Response

This investigation was designed to test (a) whether stimuli presented in the form of repeated blocks of habituation trials, as opposed to.1 single continuous series of stimuli, would produce a progressive decline. in amount of spontaneous recovery and trials to rehabituation of the skin conductance component of the orienting response; and (b) whether 30 or 50 post-habituation trials would produce a return of the orienting response which could be related In sensitization effects. Results showed that repeated habituations strengthened habituation as reflected in progressively decreasing spontaneous recovery across blocks, but not in speed of habituations. Further, neither 30 nor 50 post-habituation trials produced a return of the orienting response, although 30 such trials did result in increased skin conductance level. Discussion centers on whether habituation beyond asymptotic levels (‘below-zero’) within sessions was unambiguously obtained; relationships among stimulus intensity, frequency, and the return of the orienting response; and factors affecting measures of retention of habituation within sessions.     

Anxiety and the Habituation of the Skin Conductance Response

The effect of threat of shock on the habituation of the skin conductance response (SCR) to a series of auditory stimuli was assessed. Skin resistance and heart rate were recorded during the presentation of 20, 1 sec, 1000 Hz tones in a control session and in a session at the end of which subjects were led to expect a painful electric shock. The effects of the threat of shock consisted of recovery of the SCR and an increase in skin conductance level and heart rate. They were restricted to the period during which subjects believed the shock to be imminent. Two possible reasons for the SCR recovery were offered, one in terms of Lader and Mathews' (1968) ‘maximal habituation’ hypothesis and a second in terms of a change in the stimulus complex.     

Physiological Responses of Anxious and Normal Subjects to Simple Signal and Non-Signal Auditory Stimuli

In an attempt to assess orienting (OR) and defensive responses (DR) of anxious and normal Ss, heart rate (HR) and skin conductance (SC) changes were measured in response to three intensities of signal and non-signal tones. Anxious Ss significantly differed from normal Ss in the number of spontaneous SC responses emitted, but did not differ in either magnitude or rate of habituation of SC responses to the tones. An analysis of second-by-second changes in HR suggested that, relative to normal Ss, anxious Ss show a deficit in OR and a greater tendency to respond with a pattern characteristic of a DR. This difference was particularly apparent under signal conditions.