Quarterly Journal of Experimental Psychology

Immediate free recall of random strings of 10 numbers was studied under four experimental conditions: as each number was presented, subjects either had to recall the previous number (Recall n–1), recall the number just presented (Recall n), read the number (Read aloud), or were silent (Free Recall). Overall recall was the same in all conditions. Recall and order of recall by serial-position changed systematically, with an increasing recency and decreasing primacy effect from Free Recall through Read Aloud and Recall n to Recall n–1. These changes in recall order and serial-position curves suggest that differential rehearsal of items is decreased by requiring retrieval during presentation.

An experiment in typing is described in which the visual spacing in the text and the amount of linguistic structure in the material are varied. The results show that average typing speed is decreased both by removing visual spaces from the text and by decreasing the amount of structure in the material. The data are interpreted as evidence that there is response grouping in a typist's output, and a model is stated in which this grouping is attributed to the operation of a response-unit scanner. More detailed analysis by means of this model suggests a picture of serial and parallel information processing to be an adequate representation of the conversion of text into type.

Pigeons peck faster during a signal for reward (S+) when that signal alternates with one for absence of reward (S−). This “contrast effect” has been shown to involve diminished preference for S + compared with a stimulus not involved in a discrimination. The present experiment demonstrates that the signal produced by pecks to S+ in a chained schedule is responded to in proportion to the contrast effect during S +. The result suggests that a prior interpretation of contrast, in terms of Amsel's frustration theory, is not the correct one.

It is found that electric shock delivered before exposure to a Y-maze reduces the activity of rats whether the maze is familiar or unfamiliar. Increasing familiarity with the maze reduces activity for shocked and unshocked rats. It is argued that this finding presents difficulties for theories according to which exploratory behaviour depends on fear.

The release from PI methodology was used to test Oldfield's (1966) suggestion that human memory is organized in part on the basis of frequency of occurrence. An observed release from PI identified frequency of occurrence as an encoding category and provided support for the underlying assumptions of Oldfield's model.

Latency of a fixed ratio (FR) 3 escape response in rats was found to be a U-shaped function of the interval between training and injection of the anticholinesterase drug physostigmine, for intervals from 30 min. to 5 days between training and injection. An increase in FR 3 escape latency was found at 28 days. FR 1 escape groups produced a latency curve of a shape similar to that of the FR 3 group. These data confirm the results of earlier experiments using a different training procedure, and a different response measure. These results are consistent with the theory that the physiological correlate of rat memory lies in synaptic change.

Gibson (1950a) has suggested that a gradient of retinal stimulation from an irregularly textured surface is used in the estimation of slant. There are several measures that could form such a gradient. Eight pictures of slanting surfaces were constructed with the aid of a computer. These consisted only of texture elements: in this case, outline circles and ellipses. Subjects studied pairs of pictures and indicated which had the greater tilt. By varying separately the gradients of element size and element density, it was possible to show that only the former contributed appreciably to the impression of slant. Only some of the measures considered are consistent with this result.

A bar-pressing experiment was carried out in which laboratory rats were reinforced approximately in direct proportion to the level of time integral of force (“effort”) exerted per response. Over the course of training, the subjects increased in efficiency, as measured by amount of food obtained per unit effort exerted. It was not demonstrated, however, that the animals learned to take advantage of the effort-proportional reinforcement contingency.

After a subcutaneous injection of bovine insulin into the rat, at first there is an augmentation of the satiety produced by nutrient eaten immediately before injection. Later, with large enough doses, as has been commonly observed, feeding is elicited—perhaps simply by hastening the passage of satiety. A third type of effect is behavioural disruption, reducing food and water intake when food is withheld for an hour after injection and producing postural changes even when food is present. Fourth, repeated pairing of insulin injection with intake of water of a particular flavour (even when drunk over half an hour beforehand) depresses subsequent intake of water having that flavour, whether presented alone or together with water of another flavour which has been paired with control injections. The acquired discriminated intake change involves the initial acceptability of the flavour but changes in the inhibition of acceptability during an intake bout have not been excluded.

Egocentric visual orientation was investigated with lateral head tilts relative to the upright and supine trunk. A significant difference was found in the trend of visual head axis judgments between 40° left and 40° right head tilt for the two conditions, such that they varied systematically with the degree of tilt for the upright but not for the supine condition.

Visual orientation during lateral tilt is viewed in terms of orientation constancy. The postural systems involved in the maintenance of constancy are considered to be those of the otolith, neck and trunk. The relative contribution of these systems was investigated by obtaining visual verticality judgments immediately upon and several minutes after head, body, and trunk tilts. Due to the apparent non-adaptation of the otolith system any changes in visual orientation resulting from prolonged tilt would be attributed to adaptation of the proprioceptive system stimulated. For 30° head tilt visual orientation over-constancy was reduced by about 2°, reflecting the influence of the neck system. Prolonged body tilts of 30°, 60° and 90° reduced the constancy operating by approximately 1°, 3° and 8°, respectively. This was taken to indicate the contribution of the trunk system, which increased with increasing degrees of body tilt. The above interpretations received strong support from experiments involving trunk tilt, which stimulates only the neck and trunk systems.

Twelve undergraduate subjects classified the word-shape configurations circle/CIRCLE, square/SQUARE, circle/SQUARE and square/CIRCLE by reporting “yes” for a relationship of congruence, and “no” for a relationship of incongruence. The latency of initiation of these reports was recorded, measured from the simultaneous onset of the displays. The order in which the word and shape were inspected had consistent effects on the latency, times being shorter where the word was seen before the shape. The relevance of this finding to an account of the conversion operations involved in a word-shape comparison is discussed.

Reproduction and recognition in short-term visual memory was tested. In Experiment I, it was confirmed that the ability to reproduce visual figures in STM correlated with the ability to describe them. No such correlation was obtained when recall was by recognition. In Experiments II and III the mechanisms involved in the two types of recall were investigated by varying the character of the task interpolated in the retention interval. Results support the view that reproduction has a verbal component which is lacking in recognition.

Albino guinea pigs were trained in shuttle-boxes. Superior performances were achieved with longer CS–US (15 sec. against 5 sec.) and intertrial intervals (90 sec. against 30 sec.). There were no performance increments within sessions, but improvements in performance occurred between sessions. Consolidation mechanisms probably play an important part in avoidance learning by guinea pigs.

Four groups of rats received 0, 3, 6 or 9 days of overtraining after having reached stable performance on a continuous reinforcement bar pressing schedule. Half the subjects in each group had previously been designated emotionally reactive or non-reactive in terms of defecation rates in an open-field test. Following training, there were four test days in which bar pressing in each group was examined in the presence or absence of white noise. The major findings were that, in both the reactive and non-reactive groups, white noise produced a fear reaction which significantly depressed bar pressing at low levels of habit strength while having an energizing effect at higher levels. The results were interpreted as supporting Bardach's (1960) hypothesis that anxiety introduced early in practice is more disruptive than when introduced late in practice.

The perceptual tuning hypothesis can be expressed as a prediction that discrimination of a particular stimulus dimension will be enhanced if it is the only dimension requiring discrimination and not one of a set of dimensions in a multidimensional discrimination task. In previous tests of the tuning hypothesis, using speech material, the size of a message set has been manipulated as an indirect means of controlling the number of dimensions an observer is required to discriminate. In the present experiments the particular items appearing in a message set have been selected in order to control precisely the number of dimensions relevant to the discrimination task, and performance is estimated in terms of the discrimination of each relevant dimension. No evidence is found for a perceptual tuning effect even though it is argued that the conditions of the present experiment represent those most favourable for its elicitation.

Contralaterally presented shock was found to bring about marked changes in two shock threshold determined for the right finger but not for the left finger. The results are discussed in terms of a suggestion that the level of excitability of the left hemisphere may be more easily disturbed than that of the right hemisphere.

Twenty-eight pigeons were given discrimination training. Four groups were run in which for 0, 2, 4 and 9 sessions of training colour was an irrelevant cue and tone was relevant. Generalization tests were given in extinction; the training colour (C₁) and another colour (C₂) were presented with tone (T) and noise (N). Responding to these four stimulus combinations, TC₁, TC₂, NC₁ and NC₂, allowed the assessment of control by colour and tone. A reduction of control by colour and an increase in control by tone were found to be positively related to the amount of training with colour irrelevant. Tests showed a strong inverse relationship between control by colour and tone.

A principal component solution and varimax rotation were obtained for eight studies using a serial position (SP) probe technique for studying short-term memory. The factor pattern which emerged showed the first and middle SPs to load on one factor, called the primacy factor, while the middle and last positions loaded on a second factor, called the recency factor. The results were consistent with the view that short-term memory is composed of two processes, primary memory and secondary memory. One study supported the notion that immature humans show a rehearsal deficit.

Male mice of strains A₂G/Tb, C₅₇BL/Tb and the F₁ produced by crossing them were studied singly for 3 days in an artificial environment (a “plus-maze”), in which movement was recorded automatically. There was a central nest box with an opaque cover, from which three passageways led to food, water and soft (balsa) wood, respectively; a fourth arm was left empty. The number of visits to the arms was always highest on the first day. On a given day, the number of visits was much the same for each arm, that is, it was not influenced by the incentives. In contrast, while time spent out of the nest box was about the same from day to day, the time spent in individual arms differed greatly and was in the order food> balsa wood> water> empty arm. In terms of visits, the F₁ and C₅₇BL/Tb mice were more active than A₂G/Tb; and the F₁ mice varied less than either inbred strain. The lack of correspondence between visits and duration of stay is discussed in relation to the concept of neophilia.

Perception of size and perception of pain were studied in a group of right-handed and a group of left-handed subjects. For right-handed subjects a significant relationship was found between these two types of perception in that subjects who tended to underestimate size with the dominant hand also had a higher pain threshold for that hand as compared with the non-dominant hand.

A questionnaire technique, based on public events, for quantifying memory over long periods of time, is described. Independent groups of subjects were tested at intervals of six months on a recall and multiple choice version of the questionnaire. A consistent relationship between memory and both age of subject and passage of time was found. An error analysis is presented.

If subjects are required to make two responses at the same time, one with each hand, the responses of the hand appearing second in this sequence may be considerably delayed. The hands appear to be in competition with one another for first response. Interference of this kind was studied in an experiment in which, interspersed in a series of signals for either right or the left hand response, were a number of double signals which called simultaneously for response from both hands. Both the right and the left hands had an equal chance of taking precedence over the other, and an equal chance that their response would be delayed. The hand controlled by the dominant hemisphere responded first no more often than did the non-dominant one. A degree of synchrony developed between the responses of the hands as the subject experienced a greater number of signals for paired response.

In a second experiment the hands were required to compete with one another after practice had been given in responding with only one hand. The effects of practice were not equal and opposite across the body. Practised left hand responses were found not to be disturbed by the addition of a simultaneous signal for another response, whereas right hand responses were. This relationship exists in both right and left-handed subjects, and the results seem to point to differences in cerebral control between the hemispheres which may be related not to handedness but to side of the body as such.

One hundred and fifty 23-hr. deprived rats were run in a 2 × 5 × 3 balanced analysis of variance design to determine the effect of prior shock on food intake. The main factors were time spent in shock box (3, 30 sec.), intensity of shock (0, 0.5, 1.5, 2.5, 3.5 mA) and percentage of sucrose adulteration of food (0, 10, 25 per cent).

Results showed a general enhancement of intake following 3-sec. shock and a suppression following 30-sec. shock. Variations in shock intensity were of no significance.

Three experiments of identical design, but using different basic materials are reported. In experiment I the probability of recognizing tachistoscopically presented typed and handwritten words was found (a) when the two types of materials were presented in separate lists, and (b) when presented together in a mixed list when subjects did not know what type of material to expect next in the sequence. In Experiment II, two handwritings were employed and in Experiment III, upper and lower case typed material was used.

The mixed condition resulted in poorer performance than the unmixed condition only in Experiment I when typing and handwriting were used. In Experiments II and III, mixing had no effect.

It is suggested that different recognition programs are used for typed and hand-written characters.

Past research has proved equivocal in providing a correlation between the amplitude of cortical evoked potentials and attended or unattended stimuli. The present experiment is a further investigation of the relationship between selective attention and the cortical evoked potentials and avoids some methodological artifacts. The results of the experiment provide no direct support for the postulated correlation between the two variables, but do suggest two possible explanations of this state of affairs.

Six rats were exposed to schedules of free-operant shock avoidance. For three of these, auditory or visual stimuli were present continuously throughout each experimental session. For the remaining three rats, these stimuli were presented only 5 sec. before an avoidable shock, and were removed by any operant response to be emitted during their presence. For these latter rats, the stimuli developed strong discriminative control over the emission of operant responses. When the avoidance behaviour had stabilized, the effects were studied of a stimulus which preceded an unavoidable shock of the same intensity as that maintaining the avoidance responding. These effects were studied in the following conditions: against the ongoing avoidance behaviour; with no avoidance stimuli present; and against extinction of avoidance behaviour. With the animals exposed to continuous schedule stimuli, all these experimental conditions resulted in an acceleration of responding during the signal which preceded an unavoidable shock. The rats with the strong stimulus control of avoidance responding afforded by the discontinuous schedule stimuli never showed such an acceleration; indeed all three animals showed suppression of their operant responding in the final experimental condition. It therefore appears that experience of shock avoidance per se is not sufficient to produce the acceleration effect: the discriminative control of behaviour, or lack of it, is also implicated.