Binocular rivalry and stereoscopic depth perception

An investigation was made of stimulus factors causing retinal rivalry or allowing stereoscopic depth perception, given a requisite positional disparity. It is shown that similar colour information can be “filtered” out from both eyes; that stereopsis is not incompatible with rivalry and suppression of one aspect of the stimulus, and that the strongest cue for perception of stereoscopic depth is intensity difference at the boundaries of the figures in the same direction at each eye. Identity of colour can also act as a cue for stereopsis. The brightness of different monocular figures seen in the stereoscope in different combinations was estimated by a matching technique, and it is suggested that the perceived brightness is a compromise between the monocular brightness difference between figure and ground seen in relation to the binocular fused background, and the mean brightness of the figures. The results are discussed in terms of neurophysiological “on,” “off” and continuous response fibres.     

A further study of the pendulum phenomenon

A first series of experiments had demonstrated certain conditions eliciting or inhibiting a “pendulum” phenomenon in the visual perception of apparent movement. The present study consists of five further variations designed to show more clearly conditions of occurrence and non-occurrence of this type of movement. The main findings are:

(i) Altering the axis of display to vertical significantly reduces the frequency of pendular-movement perception;

(2) Altering the position of metronome from behind to the side of the visual display, gives results almost identical with those where the metronome was inaudible, but, when the metronome is illuminated in this position, all forms of movement perception are reduced, and no pendular movement is reported.

The results for all the ten conditions, including the five of the first series are summarized, and the following possible factors are discussed: past experience, physiological nystagmus, and intervening adaptation. All three may be required to account for the perceptual phenomena under investigation and the dichotomizing of explanations into “experiential,” or “physiological,” appears to be arbitrary and inconsistent with the complexity of the observed facts.     

The perception of three-dimensional solids

Arising from the discussion of differences between three- and two-dimensional perceptual objects in relation to current theories, an attempt is made to extend the traditional type of shape-constancy investigation into the realm of three-dimensional solids. For this purpose a specially constructed “solid” is made to undergo progressive physical changes of shape while being compared, under controlled conditions, with various stationary two-dimensional projections.

The results indicate that three-dimensional solids possess perceptual properties not shared by simple surfaces or representational projections. It is suggested that changes in the magnitude and sign of the constant errors obtained under certain conditions can be explained only on the assumption that subjects react to the stimulus in terms of some conceptual schema, or reference frame, involving mental processes other than those of perception.     

A comparison of body perceptions in relation to measured body composition in young Japanese males and females

The body composition of 139 Japanese females and 84 Japanese males (aged 18–30 years) was measured using anthropometry to assess gender differences in body perceptions in relation to their measured values. Participants were asked to rate perceptions of their own “heaviness” and “fatness” and these were compared to their BMI and percent body fat (%BF). Japanese females showed a significantly greater desire to lose body weight (−4.20 ± 0.6 kg) compared to males (0.27 ± 1.4 kg). Females also showed poor understanding of their “heaviness” and “fatness” in relation to actual body composition compared to males. The results confirmed distinct gender differences in body perception in relation to actual body composition and attitudes to weight management. Further promotion of “healthy” body image is recommended for the Japanese population.     

The perceptual-mnemonic/feature conjunction model of perirhinal cortex function

The perirhinal cortex was once thought to be “silent cortex”, virtually ignored by researchers interested in the neurobiology of learning and memory. Following studies of brain damage associated with cases of amnesia, perirhinal cortex is now widely regarded as part of a “medial temporal lobe (MTL) memory system”. This system is thought to be more or less functionally homogeneous, having a special role in declarative memory, and making little or no contribution to other functions such as perception. In the present article, we summarize an alternative view. First, we propose that components of the putative MTL system such as the hippocampus and perirhinal cortex have distinct and dissociable functions. Second, we provide evidence that the perirhinal cortex has a role in visual discrimination. In addition, we propose a specific role for perirhinal cortex in visual discrimination: the contribution of complex conjunctive representations to the solution of visual discrimination problems with a high degree of “feature ambiguity”. These proposals constitute a new view of perirhinal cortex function, one that does not assume strict modularity of function in the occipito-temporal visual stream, but replaces this idea with the notion of a hierarchical representational continuum.     

Tactile-kinaesthetic perception of straightness in blind and sighted humans

A comparison is made between the tactile-kinaesthetic perception of straightness in twenty blind and twenty sighted subjects. Both types of subject are found to perceive a “plus curved” edge as straight, but this curve is significantly less for the blind than for the sighted, i.e. the blind subjects' judgments correspond more closely to the objective straight. Furthermore, the blind, both as individuals and as a group, are significantly finer in their judgments and more consistent. These results are thought to be explained in terms of the more highly developed organisation of the blind's tactile-kinaesthetic perception.     

Aperture viewing : A review and a synthesis

We argue that two processes are involved in the visual perception of shapes moving behind narrow apertures. “Retinal painting” occurs when the eyes are free to pursue the moving shape and when the traverse time across the aperture is sufficiently short to allow visual persistence of the temporally successive views. When pursuit eye movements do not occur, however, the shape may still be perceived if it moves relatively slowly. The latter kind of perception does not involve seeing all the parts of the shape simultaneously (as in the case with retinal painting) but we demonstrate that shapes seen in this way have some of the same properties as conventionally presented shapes. The discussion emphasises the relevance of these findings to general problems in movement perception.     

A contribution to the study of phenomenal causation

In his studies of the perception of causality, Michotte describes a number of “impressions” concomitant with precisely defined experimental conditions, of which “Launching” and “Triggering” are two of the most important. Two major factors influencing the nature of the impressions are the relative speeds of the two rectangles representing objects participating in dynamic inter-relationships, and the length of path of the more passive of the two objects. This investigation was an attempt to discover the quantitative relationships obtaining between these two independent variables and the dependent variable of the subjects' responses to the experimental conditions.     

The effect of orthographic structure and lexical meaning on “same-different” judgments

Pairs of high frequency English words, orthographically acceptable pseudo-words, and non-word letter strings were presented in a “same”-“different” task. The mean reaction times for “same” judgments were ordered; real words were faster than pseudo-words, and pseudo-words were faster than non-words. The RTs for the “different”, judgments showed no differences among the three types of words, except in the first two days of practice in a blocked presentation condition when the difference between the real words and non-words was marginally significant. These and other results suggest that “same” judgments are based upon a comparison process which efficiently uses higher order semantic and orthographic information in words, whereas “different” judgments are based upon comparison process which performs a self-terminating search of the graphemic information in words. The results were also discussed with reference to hierarchical models of word perception and reading.     

Perceptual independence in the perception of speech

The purpose of the experiments and analyses was to discover whether the “independence” model, which successfully accounts for the perception of synthetic multi-dimensional stimuli, would also describe the perception of speech in noise. Two sets of four words were chosen which could be considered phonetically to be describable in terms of two dimensions. The S/R matrix was analysed as if the stimuli were bi-dimensional elementary stimuli. Satisfactory fits were obtained by the independence model. Two analyses were conducted upon data from Miller and Nicely (1955) and Conrad (1964) to discover whether the perception of phonemes was also predictable on the independence model. In general this was found to be the case.     

Early motion processes and the kinetic depth effect

It has been known for over 30 years that motion information alone is sufficient to yield a vivid impression of three-dimensional object structure. For example, a computer simulation of a transparent sphere, the surface of which is randomly speckled with dots, gives no impression of depth when presented as a stationary pattern on a visual display. As soon as the sphere is made to rotate in a series of discrete steps or frames, its 3-D structure becomes apparent. Three experiments are described which use this stimulus, and find that depth perception in these conditions depends crucially on the spatial and temporal properties of the display:

1. Depth is seen reliably only for between-frame rotations of less than 15°, using two-frame and four-frame sequences.

2. Parametric observations using a wide range of frame durations and inter-frame intervals reveal that depth is seen only for inter-frame intervals below 80 msec and is optimal when the stimulus can be sampled at intervals of about 40-60 msec.

3. Monoptic presentation of two frames of the stimulus is sufficient to yield depth, but the impression is destroyed by dichoptic presentation.

These data are in close agreement with the observed limits of direction perception in experiments using “short-range” stimuli. It is concluded that depth perception in the motion display used in these experiments depends on the outputs of low-level or “short-range” motion detectors.     

The twelfth Bartlett memorial lecture: The role of single neurons in the psychology of perception

I feel deeply honoured by your invitation to give the Bartlett lecture, and am especially glad to do so in Holland, the home of so many distinguished psychologists of sensation and perception. And there is a third reason why it has given me much pleasure, for Sir Frederick Bartlett was one of those who had an important influence on the direction of my career some 40 years ago. I had to decide whether to spend my last year at Cambridge reading psychology or physiology, so I attended a short course of introductory lectures he gave in July. About half a dozen of us sat on upright wooden chairs circled around him as he sat in an armchair, smiling benignly. The first thing he did was to tell us to close our notebooks, for he was not going to say anything that would help us to pass any exams. And I believe the very last words of his last lecture were, “So you see it is all very difficult”. I was very glad he said that, for I had in fact found it all very heavy going: my brain seemed always to be lost in clouds of uncertainty when “remembering”, “thinking”, or “perceiving” were mentioned, because there was no conceptual framework for these processes except the words themselves and others spun around them. What I was looking for were the definable quantities of physics, chemistry and even physiology, these I could handle conceptually in their geometric and functional interactions, whereas I always find a purely verbal argument about abstractions difficult to follow and impossible to believe. So this lack of any nonverbal conceptual framework was very painful.

There was one phrase I think I recall him using that particularly aroused my interest-“the effort after meaning”; intuitively this seemed to be very important, but however much effort I made the meaning never quite emerged. I had almost decided that my mistrust of words made me unsuited to a career in psychology, but all the same I put my problem about “physiology or psychology” directly to Bartlett. After finding out that I was mainly interested in problems of sensation and perception, he said he thought that E. D. Adrian's research over the last 20 years had made more difference to that subject than any results obtained from within psychology itself.     

Perceptions of speakers with minimal eye contact: Implications for stutterers

One hundred and thirty-three college students responded to percentage definitions of “good,” “minimal,” and “no” eye contact. They also judged their perceptions of a speaker with “little or no eye contact” on a semantic differential scale containing 60 polarized adjective pairs regarding personality traits. The majority of the student respondents defined an individual with “good” eye contact as looking at his/her audience/listener 90–100% of the time. This is a more stringent definition than other literature has indicated. Furthermore, speakers with little or no eye contact were judged less favorably on 70% of the items, which indicates that low eye contact adversely affects perceptions of a speaker's personality. Therefore, stutterers need to be made aware of the importance of and determinants of effective eye contact in communication. Also, the development of effective eye contact needs to be incorporated as a major goal in stuttering therapy.     

Visual imagery and verbalization with simple tachistoscopic displays

Two experiments, designed to compare the perception and retention of tachisto-scopic displays of four block capital letters and four simple “nonsense” figures are described. The results show that the letters were much better remembered and suggest that this was mainly due to the ease with which they were verbalized. The nonsense figures usually gave rise either to rapidly fading “iconic” images, or to an unstable kind of mixed imagery which was difficult to describe or remember, but in which inadequate verbalization was often a source of error. Subsidiary experiments illustrate the importance, not only of verbalization, but also of symmetry and simplicity in remembering visual display.     

Left and Right Hemifield Advantages of Fusions and Combinations in Audiovisual Speech Perception

If a place-of-articulation contrast is created between the auditory and the visual component syllables of videotaped speech, frequently the syllable that listeners report they have heard differs phonetically from the auditory component. These “McGurk effects”, as they have come to be called, show that speech perception may involve some kind of intermodal process. There are two classes of these phenomena: fusions and combinations. Perception of the syllable /da/ when auditory /ba/ and visual /ga/ are presented provides a clear example of the former, and perception of the string /bga/ after presentation of auditory /ga/ and visual /ba/ an unambiguous instance of the latter. Besides perceptual fusions and combinations, hearing visually presented component syllables also shows an influence of vision on audition. It is argued that these “visual” responses arise from basically the same underlying processes that yield fusions and combinations, respectively. In the present study, the visual component of audiovisually incongruous CV-syllables was presented in the left and the right visual hemifield, respectively. Audiovisual fusion responses showed a left hemifield advantage, and audiovisual combination responses a right hemifield advantage. This finding suggests that the process of audiovisual integration differs between audiovisual fusions and combinations and, furthermore, that the two cerebral hemispheres contribute differentially to the two classes of response.     

A study of the effect of structural information and familiarity in form perception

Two experiments were carried out to investigate the influence of structural information and familiarity on the processing of visual forms. Pairs of “well” structured and nameable and “poorly” structured and non-nameable fragmented forms were employed as stimuli. The effects of structure and familiarity were assessed by manipulating the visual hemifield of presentation and the task. In Experiment 1 stimuli were judged as being either in the same orientation or mirror-reversed, a task that does not require high-level semantic information to be processed. Experiment 2 required physically identical forms to be matched, which may use either physical or name information. In Experiment 1 “same” judgements were equivalent for both types of stimuli, and “different' judgements were longer for the “poorly” structured (non-nameable) forms. In Experiment 2 there was little overall difference between “well” and “poorly” structured forms, though response times to “well” structured (nameable) forms were slowed for right-visual-field presentations. It is suggested that familiarity may not be sufficient to provide a perceptual advantage for nameable forms, as the advantage for nameable stimuli was confined to “same” judgements in Experiment 1 and response times were shorter for non-nameable stimuli in Experiment 2. Rather, performance depends upon factors such as the computation of global shape (due to structural properties of collinearity and closure) and on the use of different kinds or representations (physical versus name) in matching.     

The effect of touch on a visually ambiguous three-dimensional figure

The effect of haptic (i.e. tactile-kinaesthetic) information on the perception of an ambiguous visual figure was investigated. The figure used was a self-luminous, threedimensional wire cube viewed in darkness. It was found that visual reversals still took place when the cube was explored with the hands, but the reversal rate was reduced and the time increased during which the cube looked as it “really” was.     

The limits of over-constancy

A number of studies have led to the generalization that there is a tendency to “overconstancy” in the perception of size. The experiments reported here suggest that over-estimation is limited to objects subtending angles of approximately 2° or less, and that objects subtending greater angles are judged fairly accurately. This raises the possibility that foveal diameter (approximately 2°) is involved.