Mediatory cue proximity and mental subnormality in the perception of rectilinear dot progressions

This study investigated the relationship between illusory displacement of sequentially presented light stimuli and their proximity to mediatory cues. Twenty-four retardates, 24 equal CA normals, and 24 equal MA normals were tested to determine the relative stabilizing effects of four different frame conditions on these groups. Illusory displacement decreased from least to most proximate cue condition, was least for the MA group, and was most for retardates It was concluded that interstimulus mediation referents, rather than restricted eye movement, facilitated veridical perception of successive light positions. nt]mis|The author extends sincere appreciation to Dr. Ralph Osborne, superintendent of the Hamilton Township school system, Mr. George Murphy, principal of Hamilton High School West, and Mrs. Isabel Robinson, principal of Kuser School, for their generous cooperation in providing students and testing space for this experiment.     

Interstimulus interval and delivery cues influence timed conditioned responding in rats

Appetitive contextual excitation supported by intertrial unconditioned stimuli was more easily overcome by timed conditioned responding in rats using quiet (Experiment 1) rather than noisy (Experiment 2) food pellet deliveries. Head-entry responding in acquisition peaked above the contextual baseline when pellet delivery occurred 10, 30, 60, or 90 s after the onset of the 120-s white-noise conditioned stimulus (CS). Special tests in extinction revealed CS onset and offset were conditioned by pellet delivery at 0 and 120 s, respectively. Responding was not undermined in Experiment 3 when noisy pellet deliveries replaced quiet pellet deliveries. Our results suggest that micro-stimuli occasioned at different times during the CS are vulnerable to overshadowing, but do not lose strength if they are already predictive.     

Local rates of inbreeding and severe mental subnormality in N. Ireland

The prevalence of severe mental subnormality in N. Ireland has increased at a relatively high rate during the last century, and the present level is higher than that in the rest of the U.K. It has been suggested that changes in the population structure have had adverse genetic consequences which, along with an increase in the level of inbreeding in certain areas, have given rise to much of the increased prevalence of subnormality. The rate of severe subnormality is not geographically uniform, and there are many examples of townlands with very high rates in close proximity to ones with rather low rates. This provokes a test of the hypothesis that variation in subnormality rates is underpinned by differences in inbreeding levels. Two pairs of townlands, one from the north and one from the south of the province, were chosen for study. One townland in each pair had a strikingly high rate of subnormality. The technique of isonymy was used to calculate the inbreeding coefficient (F) over 5 consecutive 25-yr periods from 1849 to 1973. There were consistently higher inbreeding levels in the towns which exhibited high rates of subnormality. The findings are discussed in relation to similar research in this area, and suggestions for future lines of enquiry outlined.     

The perception of continuous curves in dot stimuli

Two categorisation experiments are reported in which the perceptual phenomenon that some simple arrays of discrete dots appear as a continuous curve whereas others are perceived as an angular contour or as consisting of separate groups of dots was investigated. Triplets of dots were presented in the first experiment, and complete or incomplete regular dot polygons (ie dots positioned on the vertices of imaginary regular polygons) in the second. In both experiments the perception of a curve versus an angle was determined mainly by the relative orientations of the dots, ie by the angles between successive virtual lines, whereas the lengths of the virtual lines had relatively little influence. In experiment 2 the number of displayed dots was shown to be a second independent factor for perceiving continuity. These results are in agreement with results from experiments on dipole textures discrimination, and suggest the psychological existence and importance of virtual lines in the visual processing of dot stimuli.     

Conversational skill and locus of perception

The present study attempted to identify behavioral skills associated with global perceptions of communication competence and to determine if the relationship between competence and skills varies as a function of perceptual locus. Fifteen dyadic conversations were videotaped. Each interactant rated self and partner and was rated by four observers who viewed each tape. Results indicated that subjects' perceptions of their partners' skills accounted for 87% of the variance in subjects' ratings of partners' competence and 80% of the variance in subjects'self-perceived confirmation. Observers' ratings of subjects' skills predicted 83% of the variance in observers' ratings of subjects' competence. Observers'ratings of subjects'skills were unrelated to subjects' self-rated competence.     

On the locus of redundancy effects in a letter-detection task

It takes longer to detect a target if it is the initial letter of a nonredundant letter string such as BNHTW than if it is the initial letter of a redundant letter string such as BBBBB (Johnson, 1986b; Johnson & Blum, 1988). The results of the present study reveal that the redundancy effect also occurs for mixed-case letters strings (e.g., BbbBb) and digit strings (e.g., 22222). In addition, these results suggest that the cause of the redundancy effect is not related to the visual properties of the noninitial letters per se but is instead related to the presence of the target in noninitial positions. Together, these results rule out a number of hypotheses about the cause of the redundancy effect and suggest that the locus of this effect is in processes involved in response selection and/or the read-out of information from the perceptual system.     

Second-order conditioning of the rabbit's nictitating membrane response. Interstimulus interval and frequency of CS-CS pairings.

Second-order conditioning of the rabbit's nictitating membrane response (NMR) was investigated when second-order trials (CS1-CS2) were intermixed with first-order trials (CS2-US) from the outset of training. Experiment 1 showed that CR acquisition to CS1 was inversely related to the CS1-CS2 interval but nevertheless extended to an interval of 8,400 ms. Experiment 2 revealed that CR acquisition of CS1 was an inverted-U function of the number of CS1-CS2 trials relative to a fixed number of CS2-US trials. Experiment 3 directly contrasted second-order conditioning with a reinforced serial compound procedure (CS1-CS2-US) and a mixed procedure in which second-order trials were intermixed with the reinforced serial compound. Second-order conditioning was about half the strength of either the reinforced serial compound or the mixed procedure, which were similar. The present results are discussed with respect to the relative strength of excitatory and inhibitory processes in second-order conditioning.     

Redundancy in the perception of bilateral symmetry in dot textures

Redundancy in the perception of bilateral symmetry in dynamic dot textures was investigated using two-alternative forced-choice techniques. It was found that the symmetry information utilized by the visual system fell within a strip approximately 1 deg wide about the central axis of symmetry, irrespective of the size of the texture at the retina. Outside this strip, the symmetry information was found to be completely redundant.     

Hypnotic susceptibility and the perception of afterimages and dot stimuli

Three experiments were conducted to determine the relationship between hypnotic susceptibility level and the susceptibility to several perceptual phenomena. Experiment I required subjects to observe an induced afterimage in a light-proofed environment and to report the frequency of direction and color changes. In addition, subjects reported the persistence of the afterimage. Experiment II involved the observation of a black dot against a white background, with frequency of observed movement being the dependent measure. Experiment III was similar to the second experiment except that the stimulus was encompassed by a frame. In Experiments I and II, subjects judged high in hypnotic susceptibility reported perceiving the strongest effect. This phenomenon was virtually eliminated in the third experiment. These results were interpreted as supporting a process whereby subjects judged high in hypnotic susceptibility are better able to selectively attend to relevant cues in a stimulus array during conditions of perceptual impoverishment.     

The role of structural redundancy in the perception of visual targets

Most visual images contain “gross shapes” which are highly correlated with less perceptable “details,” e.g., the gross outline of a head and details such as eyes, ears, etc. The role of such structural redundancy in perception is considered both from a “syntactical” and “spatial-frequency” view of structure. An experiment is reported and evaluated in terms of a simple mathematical model which allows one to isolate the influence of several factors in the perceptual process, particularly the observer’s actual sensitivity to specific details and the influence of the redundant (correlated) information in “higher order forms,” The basic idea is that one decides whether a particular (target) detail is present in a briefly presented image by integrating impressions from various parts of the image in a weighted manner, with the weights determined by redundant information in “higher order forms.” Furthermore, the results are generally consistent with the notion that an increase in the number of attended letters does not reduce the information extracted from each letter.     

Parental perception and perceived locus of control in psychopathology

The intrusion of anxiety and disruption of ego functions seen in the more serious forms of psychopathology would seem incompatible with maintenance of an unimpaired sense of personal identity. The present study took the position that the psychiatric patient's fragile or poorly developed sense of his own identity would be reflected (a) in deficient or tenuous identifications with parental norms and values and (b) in the perception of less parental supportiveness and warmth, relative to nonpsychiatric patients, and (c) would lead the individual to perceive reinforcement as contingent primarily upon some external locus of control, rather than upon his own relatively enduring personal characteristics Support was obtained for (b) and (c), above, but not for (a).     

The effect of interval and number on masking with dot bursts

Bursts of dotted visual noise can interfere with the recognition of dotted alphabetic characters during the period following the presentation of the character. The magnitude of this interference is a function of both the number of dots and the interval between the character and the visual noise burst. The nature of this interaction is explored in this paper and, on the basis of the results obtained, an attempt is made to clarify current notions of the period of interaction surrounding real time visual events.     

The effects of sex, age, and interval duration on the perception of time

The present experiment examined the interactive effects of sex, age, and interval duration on individual’s time perception accuracy. Participants engaged in the duration production task and subsequently completed questionnaires designed to elicit their temporal attitudes. The overall group of 100 individuals was divided evenly between the sexes. Five groups, each composed of 10 males and 10 females, were divided by decades of age ranging from 20 to 69 years old. The specific time estimation task was an empty interval production procedure composed of 50 trials on each of four different intervals of 1, 3, 7, and 20 s, respectively. The presentation orders of these intervals were randomized across participants but yoked across the sexes within each of the respective age groups. Analysis of the production results indicated significant influences for the sex of the participant while age did not appear to affect estimates of these short durations. Temporal attitudes, as reflected in responses to time questionnaire inquiries, did however exhibit significant differences across age. The contending theoretical accounts of such sex and age differences are considered and explanatory accounts that present a synthesis of endogenous and exogenous causal factors are discussed in light of the present pattern of findings.