Quarterly Journal of Experimental Psychology

In each of four experiments (three using pigeons as the subjects and one using rats) animals in an experimental condition were given exposure to a pair of stimuli that subsequently they were required to discriminate between. During the exposure phase response to either stimulus was consistently followed by reward. These subjects were uniformly found to be retarded in learning the discrimination when compared with control subjects that received equivalent pre-training in the absence of the critical stimuli. These results provide no support for the suggestion that stimuli may become “perceptually differentiated” during the pre-training phase but are consistent with the proposal that novel stimuli possess a high level of associability that declines as a result of experience.

Five experiments investigated the extent to which the exteroceptive context, present on a saccharin aversion conditioning trial with rats, controlled the resulting aversion on one-bottle extinction tests and subsequent preference tests. The presence or absence of the specific odour which had been present on the conditioning trial was found not to influence saccharin intake on extinction tests, whereas the presence of the particular compartment in which, and the bottle from which, the saccharin had been consumed greatly suppressed saccharin intake as compared to the absence of these elements. Preference tests, performed in the respective conditioning contexts, showed extinction to be specific to the compartment + bottle context: groups that had extinguished their saccharin aversion in a context different from the conditioning context, retained their aversion in the conditioning context. No such specificity was found for the odour context. However, in the absence of the taste stimulus during the extinction phase, the odour that had been present on the conditioning trial did control the amount of water consumed, whereas the compartment+bottle context did not. Moreover, on preference tests, groups that had consumed water during extinction in the presence of the odour context, evidenced a lesser saccharin aversion than groups not exposed to the odour. The results are interpreted as demonstrating that rats learn about taste, odour, cage and bottle stimuli on a taste-aversion conditioning trial, and that taste and bottle stimuli seem to be the most salient.

Rats, trained to press a lever for sucrose reward on a random interval (RI) schedule, were presented while lever-pressing with two stimuli, each associated with a different schedule of shock delivery: in the presence of one stimulus (S_e), shock occurred on an RI schedule irrespective of the rat's behaviour; in the presence of the other (S_p) shocks were programmed by the same schedule but delivered only when the rat pressed the lever. Both stimuli suppressed lever-pressing. In addition, the rats developed significantly different response rates in the two stimuli, thus demonstrating a discrimination between response-contingent and response-independent shock. Group data showed faster responding in S_e than in S_p, supporting the view that response-contingent shock produces greater suppression than response-independent shock. Individual animal analyses, however, demonstrated that this was the case in the majority of animals, but not in all. Response suppression was alleviated by amylobarbitone sodium (15 mg/kg) or chlordiazepoxide HCI (5 mg/kg); the latter drug alleviated suppression significantly more in S_p than S_e and eliminated the difference between the response rates controlled by the two stimuli.

In recent years hypothesis theory has been applied to transfer between problems and thus used to explain a variety of transfer phenomena. A version of the theory is presented which leads to the prediction that identical variations in identical problems can lead to opposite trends in speed of solution of a critical problem depending on the nature of that problem. Using numerical tasks it was demonstrated that identical variations in preliminary problems either can transform a normally simple problem into an insoluble one or alternatively an insoluble problem into a simple one with the only alteration being in the degree of similarity between the hypotheses required for the initial problems and the critical problem. Implications for Einstellung, the sequence effect and general problem solving are discussed.

Recent studies on processing linguistically-derived, artificial set inclusions have generally found poor performance on true-false verification tests. Results have indicated logical processing errors, mainly conversions (e.g. if told All As are Bs, then responding true to the test statement All Bs are As). The present experiment attempted to reduce the occurrence of these errors by providing repetitive study of and test on the same set inclusion structure and immediate feedback on each true-false test sentence. Conversion errors were reduced, but only for about one-half of the subjects. Reaction time profiles for these subjects indicated an integrated, holistic representation of the set inclusion information. These reaction time data were like those observed for artificial linear orderings.

An experiment is reported in which subjects had to choose referents for pronouns in sentences such as: John blamed Bill because he spilt the coffee. To examine whether the choice of referent is influenced by features of the main verb or by the events described in the sentence, the relation between the events was altered by changing the conjunction. A significant effect of conjunction was obtained, but only when both antecedents matched the gender of the pronoun. When only one antecedent matched the pronoun, referents were chosen faster. From these results it is argued that readers use general knowledge to select referents for pronouns when gender does not identify a unique referent. A further effect of sentence structure on the time taken to select a referent was interpreted as showing that subjects analysed the sentences clause by clause.

Two experiments tested the effects of suffixes on the recall of tactual and visual sequences of alphabetic characters presented at 19 letters per min. Scoring techniques allowed for the differentiation of losses of item and order information. In Experiment I performance decrements were found for both modalities, which were mainly caused by item loss at the more recent part of the serial position curve in the suffix conditions. In Experiment II, these effects were replicated and a non-alphabetic suffix led to greater decrements for both modalities than an alphabetical suffix. While a suffix effect based on the loss of item information is consistent with a sensory trace interpretation of the suffix effect, the presence of a visual suffix effect with slow stimulus presentation is not. Additionally, the greater effect of the non-alphanumeric suffix challenges attentional interpretations. Some possible explanations are proposed.

Observers’ accuracy in detecting a narrow spatial gap between two brief, luminous rectangles presented successively was determined within a two-alternative, forced-choice procedure. This successive-field task requires iconic memory, because the information (rectangle position) in the two presentations must be combined for successful gap detection. On this task, the effect of varying the duration of the first rectangle was systematically investigated over several target luminance levels and for several ISI conditions between rectangles. At the long ISI conditions (100 and 300 ms), the effects of increasing stimulus duration was to improve performance. However, at the brief ISI condition (20 ms), increasing stimulus duration initially depressed task performance. It was found that, with practice, this initial performance drop largely disappeared, and the beneficial influence of increasing target duration was again obtained. These results are discussed in terms of (a) a proposed retinal locus for the iconic memory involved and (b), at a more general level, the potentially distracting role of changing stimulus dimensions on a task employing transient stimuli as in the present study.

Fifty-six subjects each listened to four types of dichotic input: digit-digit, tone-tone, digit (left ear)-tone (right ear), and tone (left ear)-digit (right ear). When digits were paired with tones, performance improved substantially over that with digit-digit and tone-tone input, and material-specific ear differences disappeared. The results indicate that both capacity limitation and an advantage of the contra-lateral over the ipsilateral input appear only when inputs from the two ears compete for the same kind of processing.

The relationship between the Gray and Wedderburn effect, the channel alternation effect and the class alternation effect was studied in dichotic and bisensory experiments using physically and semantically distinguishable word classes. With dichotic presentation all three effects were found to occur, but with bisensory presentation neither the Gray and Wedderburn effect nor the class alternation effect was detected. There were no significant differences between physically and semantically based grouping. The present investigation provides support for Broadbent's claim that the Gray and Wedderburn effect depends on the occurrence of the class alternation effect. The various dichotic and bisensory grouping effects are explicable in terms of selection by modality-specific processing systems.

Two experiments were performed to evaluate the influence of movement frequency and predictability on visual tracking of the actively and the passively moved hand. Four measures of tracking precision were employed: (a) saccades/cycle, (b) percent of pursuit movement, (c) eye amplitude/arm amplitude, (d) asynchrony of eye and hand at reversal. Active and passive limb movements were tracked with nearly identical accuracy and were always vastly superior to tracking an external visual target undergoing comparable motion. Proprioceptive information about target position appears to provide velocity and position information about target location. Its presence permits the development of central eye-movement programmes that move the eyes in patterns that approximate but do not exactly match, temporally or spatially, the motion of the hand.

Three experiments were performed to evaluate the influence of active and passive limb movements on adaptation to visual displacement. Over a wide frequency range (0·5-1·25 Hz) with constant amplitude, 30°, significant adaptation was achieved with active and passive movements. When arm movement frequency was constant at 1·0 Hz but amplitude of movement was varied, less adaptation was achieved for both active and passive movements than when amplitude was held constant. Even at a frequency above that of most naturally occurring limb movements, 1·67 Hz, and with variable amplitude motion, significant adaptation was achieved with active and passive limb movements. These findings emphasize the importance of visual-proprioceptive discordances for adaptation to visual displacement when only sight of the hand is permitted. Significant differences did not appear between the active and passive movement conditions in any of the experiments.

When two superimposed moving dot fields are presented simultaneously, their axes of movement appear shifted away from each other. The shift only occurs when the two directions are within 90° of each other, and is directly comparable to that which results from adapting to one and testing on the other direction. This effect is taken as further evidence for a distribution-shift model in the direction domain. It is argued that the currently accepted model of movement detection, which restricts itself to comparisons only between oppositely-tuned direction detectors, should be elaborated to include comparisons across a very wide range of detectors.

Subjects were required to look saccadically at single targets selected from one- or two-dimensional arrays of different numbers of possible alternative targets. Saccadic latencies varied with the direction but not the distance of the target, with practice and with individual subject. The effect of number of alternatives was complex, and it is suggested that an important factor influencing saccadic latency is not the number of targets per se but the number of possible directions in which a saccade may have to go.