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The preception hypothesis holds that when an aversive stimulus is made predictable in time, S may be able to inhibit his arousal response to that stimulus and thus reduce its aversiveness or impact. In response to a paper by Furedy and Klajner, which questions the validity of the preception hypothesis, it is argued that considerable behavioral and autonomic response data seem to support this hypothesis. The present authors, in particular, do not share Furedy and Klajner's view that OR theory developed to explain habituation should also be adopted to account for the findings attributed to preception. On the contrary, preception is proposed to be a distinct process playing a role complementary to that of habituation, more labile and also more effortful in the sense that it requires the involvement of the “second signal system,” while habituation can apparently proceed as a non-cognitive, automatic process. However, Furedy and Klajner's discussion suggests the fruitfulness of additional investigations to test more decisively differential predictions based on an habituation vs a preception position. Even if accepted the preception mechanism could ultimately be incorporated in an elaborated version of OR theory.

Three variables involved in the production of Short Term Physiological Activation (STPA) were identified: a) frequency of usage of the stimulus by the organism, b) relevance of the stimulus to the organism, and c) whether or not a verbal response to the stimulus is required. Stimulus sequences for information detection were constructed by combining these variables, and physiological responsiveness was observed in the GSR. It was hypothesized that short term physiological responsivity could be manipulated in an ordered fashion using combinations of the above-mentioned variables. Each one of 54 Ss was tested in six experimental sequences. It was found that it was possible to manipulate the contrast between the GSRs emitted by the S to the critical stimuli, and those produced to the alternative stimuli in information detection tasks in the predicted direction.

Relations between orienting response and span of immediate memory were studied by measuring skin potential responses (SPR) and heart rate (HR). Four conditions were studied by presenting letters in a tachistoscope and a 1000 cycle, 100 db tone simultaneous on some but not all trials. The conditions (15 Ss in each) were: tone and letters for 10 trials, then letters alone for 10 trials; tone and letters for 20 trials; only letters for 10 trials, followed by letters and tone for 10 trials; and only letters for 20 trials. The results showed: (1) positive SPR habituated and negative did not, (2) tone produced more SP activity, (3) HR showed a shift from acceleration to deceleration over 20 trials, but tone had no influence, (4) tone had no direct influence on span scores, (5) Ss showed improvement in number ol letters reported correctly. There was a significant correlation between span and negative SPR when tone was sounded (r =. 36).

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.

Averaged cortical evoked responses in man to repetitive informationally complex pictorial stimuli, as opposed to other visual stimulation, were obtained from scalp electroencephalographic (EEG) recordings. The method used involved the projection of lantern slides. Included were three different categories (indifferent scenic, repulsive medical, and nude female photographs) assumed to evoke, respectively, neutral, negative, and positive reactions in the normal young male subjects. In all subjects, recordings from occipital or occipitoparietal scalp leads consistently resulted in evoked response patterns to pictorial slides measurably differing from responses to these same slides made non-associational through defocusing, or to blank light flashes. Responses to pictorial stimuli were also different than those to motivated observation of projected words, colors, or geometric patterns. The evoked responses to the three different categories of pictorial stimuli also showed significant differences. These differences were not as marked and were clearly replicable only for some subjects.

The reported studies attempted to evaluate the influence of stimulus set size on the efficiency of detection of information through the analysis of GSR responses. Three stimulus set size variations of a standard card detection test were employed. No significant reduction in absolute detection scores was found as the number of cards was increased, and an analysis based on the Theory of Signal Detection also suggested better autonomic discrimination as the stimulus set size increased. The results suggest that the subject responds to the stimuli by dividing them into a single relevant stimulus and a reject category containing all others.