Quarterly Journal of Experimental Psychology

The results of a series of experiments on learning to reproduce a precise pressure are described and discussed in relation to a tentative hypothesis about the importance of timing of feedback signals. The evidence supports the contention that a careful analysis of the perceptual aspects of performance is necessary to account for the acquisition and retention of a precise motor response. Whilst the original hypothesis is sustained, other factors leading to the same result are clearly important. New evidence is produced which strongly suggests that cues presented simultaneously in two modalities interact. A possible distinction between sensory feedback which is used to control a response and feedback which cannot so be used, and the relation of this distinction to the learning of the response is also discussed.

Information theory concepts have been discussed in relation to data from choice reaction time experiments. Specifically, it has been stated that choice reaction time is proportional to the logarithm of the number of randomly appearing alternative stimuli. It is suggested that the reported increase in choice reaction times with an increased number of alternatives is the result of insufficient practice. Data are provided to show that, with sufficient practice, this increase does not occur between two and four choices.

An investigation of the relative discriminability of circles and squares, and circles and triangles for octopus is described. The main findings were: (1) The three pairs of figures, circle and square with base horizontal, circle and square with base at 45° to the horizontal, circle and equilateral triangle were equally discriminable for the octopus. (2) Complete transfer occurred to larger and smaller figures. (3) No transfer occurred from a square in one orientation to a square rotated through 45°, nor did training with the square in one orientation lead to any saving when the discrimination was relearned with the square in the other orientation. (4) No transfer occurred from a square to a pentagon. (5) The method of training with reward on every positive trial leads to quicker initial learning of a discrimination than training with reward only where the positive figure is attacked, but discriminatory performance with the two methods approached the same asymptote. The results are in agreement with findings with other animals where these are available for comparison.

This paper is concerned with the ability to recognize settings of a rod (pivoted at the centre) at various angles of tilt without the use of vision. Five angles of tilt, all within the upper right quadrant, were used and 80 subjects took part in the experiments. It is shown that tactile-kinaesthetic recognition of a given angle of tilt is decidedly poor, subjects commonly reporting that the position of the rod had been changed. The direction of these subjective shifts was found to be in general towards the centre of the quadrant. If, following the recognition experiments, the subjects were required to judge settings of the rod in fact vertical and horizontal, errors made tended to be in a direction opposite to that normally found in making these judgements. It was further found that attempts to reinstate the original settings led to mean judgements equivalent to those given on the recognition tests, but with signs reversed. These various phenomena are ascribed to lability and disorganization of the tactile-kinaesthetic framework. An analogy with the autokinetic phenomenon is adduced.

The relations between finger localization and various types of finger praxis were assessed by estimates of the inter-correlations among the performance of 100 six-year-old children. Finger localization was related significantly to those types of finger praxis which involve movements of the individual fingers with respect to each other. Right-left discrimination was related to finger localization, but not to the measures of finger praxis.

The findings are interpreted in terms of the construct of the finger schema, which can be viewed as a determinant of performance in both the localization and praxis tasks. This construct can also serve as an explanation of the observed concurrence of finger agnosia and finger apraxia as a consequence of cerebral disease.

The case is described of a man in whom certain percepts of central origin (after-images of hallucinations) fluctuated rhythmically with the arterial pulse. The phenomenon is explained in terms of contemporary theories of consciousness and the inhibitory effects of baroceptor impulses.

In a previous communication (Oswald, 1957) it was described how some persons may experience visual after-images not only after retinal stimulation but also after the prolonged contemplation of a voluntary vivid image (hallucination). One of those described, Subject Wi, is further discussed below. It is relevant to this case and to the interpretation suggested, to recall that Griffits and Gordon (1924) described the rhythmical increase and decrease of the size, intensity, or apparent distance of vivid images (hallucinations) with rhythmical fluctuations of vasomotor tone, of pulse rate and, by inference, of blood pressure.

Subjects were instructed to equate the brightness of two stimuli of different areas presented alternately to the far periphery. The results are closely describable by IA = k (Ricco's Law), indicating that the subjects equated total luminous flux. It is suggested that these results and certain other behavioural and anatomical considerations make it unnecessary to consider flux discrimination a “subcortical” or “lower” visual function as compared with brightness discrimination.

In shadowing one of two simultaneous messages presented dichotically, subjects are unable to report any of the content of the rejected message. Even if the rejected message consists of a short list of simple words repeated many times, a recognition test fails to reveal any trace of the list. If numbers are interpolated in prose passages presented for dichotic shadowing, no more are recalled from the rejected messages if the instructions are specifically to remember numbers than if the instructions are general: a specific set for numbers will not break through the attentional barrier set up in this task. The only stimulus so far found that will break through this barrier is the subject's own name. It is probably only material “important” to the subject that will break through the barrier.