Recognition of tachistoscopically exposed letters by normals and retardates’

Thirty adolescent educable retardates,30 equal-MA normals, and 30 equal-CA normals were tachistoscopically presented a square array of four letters at two exposures (.01 sec and .3 sec). The groups did not differ significantly in correct recognitions at the shorter exposure and the two older groups had significantly better recognitions in the right visual field than the left. Under the longer exposure the groups ordered from poorest to best performance: retardates, equal-MA normals, and equal-CA normals; and no group recognized significantly more letters on one side than the other. Results were discussed in terms of consistency of reporting patterns which aided recognition.     

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.     

The von Restorff effect and measures of organization in normals and retardates

Thirty-two noninstitutionalized retardates and 32 normals of equal mental age (approximately 8 years) heard 10 orders of 10 nouns when the decibel (dB) level of the stimuli was the same and when the dB level of the sixth item was higher. The yon Restorff effect was demonstrated by both groups. The normals’ overall recall was superior to that of the retardates’ recall. Differences in recall were attributed to the normals’ tendency to recall items in the same serial order more consistently. The subjective organization of lists, as measured by order of recall, differed for the normals and retardates; the normal group was more adaptable than the retarded group in adjusting their strategy to different list conditions.     

Intentional and incidental visual memory as a function of cognitive level and color of the stimulus

Performance of two groups of youngsters, educable mentally retarded (CA 15-5; MA 11-4; IQ 74.3) and those of average ability (CA 10-5; MA 11-3; IQ 109.1) was compared for intentional and incidental visual memory as a function of cognitive level and color of the stimulus. Nonretarded subjects performed significantly better than the retarded ones of equal MA. Both groups performed better with a color than black-white card, and both groups did better on the tasks involving intentional rather than incidental memory.     

Acquisition and transfer of conceptual learning by normals and retardates: the effects of modeling, verbal cues, and reinforcement

The present study compared the effects of modeling, verbal cues, and reinforcement on conceptual learning of normals and retardates. Performance on both original learning tasks and a transfer task was examined. The results indicated that, relative to a control group, modeling alone, modeling plus verbal cues, and exposure to the completed task plus verbal cues facilitated original conceptual learning. Furthermore, modeling plus verbal cues was more effective in reducing errors than modeling alone. Original learning was not affected by tangible reinforcement, social reinforcement, or IQ level. No significant effects were found for a transfer task.     

The psychophysiology of the visual thought perception of visually evoked brain potentials and recognition mechanisms

The study tries to demonstrate, that the combination of the actualgenetic method (Sander, Froehlich), and the VEP, allows a systematic and differentiated analysis of the psychophysiological process of visual thinking. A student group was compared with mental retardates in VEP and EOG, watching actualgenetically manipulated picture series. Phasic EEG-changes are significantly related to the identification process. Most sensitive are amplitude changes about 120 to 270 msec. The mental retardates had significant VEP changes 180--270 msec, the students 128--192 msec after picture presentation. The process factor analysis (Pawlik) elaborated an illumination factor and two factors being labelled general reaction set. VEP averaging over the persons revealed different attention and/or discrimination behavior for the student group and the mental retardates, identifying the picture objects.     

Unimanual and bimanual continuous movements benefit from visual instructions in persons with down syndrome

ABSTRACT The authors' aim was to understand how persons with Down syndrome (DS) perform different tasks and to assess if there were any differences in performance based on the type of instructions. This is important because of neurological differences in persons with DS and neurological demands for performing different types of tasks. Twenty right-handed participants with DS, 20 chronological age-matched (CA), and 20 mental age-matched (MA) performed unimanual, bimanual, discrete, and continuous drumming following visual, auditory, and verbal instructions. Overall, discrete drumming was performed with shorter movement times than continuous drumming and unimanual drumming was performed with shorter movement amplitude than bimanual drumming. With respect to instructions, persons with DS performed with smaller amplitudes, thus more efficient movements, following the visual instructions than auditory and verbal instructions for all types of tasks, whereas CA performed similarly with all instructions and MA performed with smaller amplitudes with visual instructions than auditory instructions. These results suggest that visual instruction provides the best information for people with DS to aid in performance of many different types of movements.     

Perceptual organization of line configurations: Is visual awareness necessary?

We examined whether configuring, which determines the appearance of grouped elements as a global shape, requires visual awareness, using a priming paradigm and two invisibility-inducing methods, CFS and sandwich masking. The primes were organized into configurations based on closure, collinearity, and symmetry (collinear primes), or on closure and symmetry (noncollinear primes). The prime-target congruency could be in configuration or in elements. During CFS, no significant response-priming was observed for invisible primes. When masking induced invisibility, a significant configuration response-priming was found for collinear and noncollinear primes, visible and invisible, with larger magnitude for the former. An element response-priming of equal magnitude was evident for visible and invisible noncollinear primes. Our results suggest that configuring can be accomplished in the absence of visual awareness when stimuli are rendered invisible by sandwich masking, but it benefits from visual awareness. Our results also suggest sensitivity to the available grouping cues in unconscious processing.     

The effect of an after-coming random pattern on the perception of brief visual stimuli

The perception of briefly exposed visual forms is shown to be masked by an after- coming random pattern stimulus of approximately equal intensity. This effect occurs only under certain well defined conditions; it is limited by the minimum stimulus exposure time in excess of threshold which overcomes masking (critical stimulus duration) as well as by the minimum interval between presentation of the two stimuli which permits evasion of the masking action (critical interval). Over the range of stimulus duration in which masking occurs, critical interval varied with stimulus duration in such a way that the interval multiplied by the stimulus duration equals a constant. Critical stimulus duration and critical interval at threshold are shown to vary little under a variety of conditions. The effect of the random pattern stimulus is limited to the part of the visual field to which it is presented.     

What's in a mask? Information masking with forward and backward visual masks

Three experiments tested how the physical format and information content of forward and backward masks affected the extent of visual pattern masking. This involved using different types of forward and backward masks with target discrimination measured by percentage correct in the first experiment (with a fixed target duration) and by an adaptive threshold procedure in the last two. The rationale behind the manipulation of the content of the masks stemmed from masking theories emphasizing attentional and/or conceptual factors rather than visual ones. Experiment 1 used word masks and showed that masking was reduced (a masking reduction effect) when the forward and backward masks were the same word (although in different case) compared to when the masks were different words. Experiment 2 tested the extent to which a reduction in masking might occur due to the physical similarity between the forward and backward masks by comparing the effect of the same content of the masks in the same versus different case. The result showed a significant reduction in masking for same content masks but no significant effect of case. The last experiment examined whether the reduction in masking effect would be observed with nonword masks--that is, having no high-level representation. No reduction in masking was found from same compared to different nonword masks (Experiment 3). These results support the view that the conscious perception of a rapidly displayed target stimulus is in part determined by high-level perceptual/cognitive factors concerned with masking stimulus grouping and attention.     

What's in a mask? Information masking with forward and backward visual masks

Three experiments tested how the physical format and information content of forward and backward masks affected the extent of visual pattern masking. This involved using different types of forward and backward masks with target discrimination measured by percentage correct in the first experiment (with a fixed target duration) and by an adaptive threshold procedure in the last two. The rationale behind the manipulation of the content of the masks stemmed from masking theories emphasizing attentional and/or conceptual factors rather than visual ones. Experiment 1 used word masks and showed that masking was reduced (a masking reduction effect) when the forward and backward masks were the same word (although in different case) compared to when the masks were different words. Experiment 2 tested the extent to which a reduction in masking might occur due to the physical similarity between the forward and backward masks by comparing the effect of the same content of the masks in the same versus different case. The result showed a significant reduction in masking for same content masks but no significant effect of case. The last experiment examined whether the reduction in masking effect would be observed with nonword masks—that is, having no high-level representation. No reduction in masking was found from same compared to different nonword masks (Experiment 3). These results support the view that the conscious perception of a rapidly displayed target stimulus is in part determined by high-level perceptual/cognitive factors concerned with masking stimulus grouping and attention.     

fMRI of developmental stuttering: a pilot study

The purpose of this investigation was to explore the feasibility of fMRI in the study of developmental stuttering. Speech contrasts (loud versus silent reading) and language contrasts (reading of semantically meaningful text versus nonsense words) of six developmental stutterers and six nonstutterers were compared using a commercial 1 Tesla MR-Scanner (Siemens Expert). Results indicate that mapping cortical function in persons who stutter is indeed feasible, even with a 1TMR-system. Compared to normals the stutterers seemed to employ different and particularly less differentiated auditory and motor feedback strategies in speech. They apparently rely on auditory processing and on cerebellar contribution as much during silent reading as during reading aloud. Moreover, they showed a greater involvement of the right hemisphere in language processing, activating not only the typical language areas on the left but also and with equal magnitude the right side homologues of these areas. In spite of the promising results, at present several practical problems such as possible movement artifacts and possible masking through scanner noise still hamper a more straightforward use of fMRI in the study of developmental stuttering.     

Selective attention in cerebral palsied and normal children

Noninstitutionalized, educable retarded, spastic cerebral palsied children of two mental age (MA) levels were compared with normal MA controls on a task measuring selective attention and were not found deficient in selective attention. For both the cerebral palsied and the normals there was an increase in selective attention efficiency with an increase in MA. The results support the position that MA rather than chronological age or IQ is the important variable in determining selective attention performance. The results do not support the attention-deficit theory; they do support the argument that institutionalization has a negative affect on attention. The effects of brain damage and retardation on selective attention ability were discussed.Thanks are expressed to Eleanor Rennie, Head Teacher, Robert Massie, Supervisor of Special Education, and E. F. DeFord, Assistant Director, Department of Research for the Richmond Public Schools, Richmond, Virginia. Appreciation is also given to Scott Hamrick, Principal, Jackson Via Elementary School, Charlottesville, Virginia. Susan Autrey is also thanked for assistance in data collection.     

Comparison of schizophrenics and normals on a visual search task.

The response times of 16 paranoids, 16 nonparanoids and 16 normals were compared on a search task which required subjects to identify target letters embedded in displays of varying numbers of non-targets. The rate on increase in response times with increased numbers of letters displayed was not markedly different for the various groups, although a derived measure of decision and response-selection time indicated that normals selected responses more rapidly. When compared with normals, schizophrenics seemed to experience more difficulty in response selection and decision than in processing visual stimulus information.     

Representational development of the human figure in familial retardates.

Representational development of the human figure of normal and familially retarded children was examined. Five tasks were employed: Drawing a Person, Figure Completion, two Form Puzzles, and Drawing on Dictation. Ss included 34 normal children, ages 3-0 to 5-10, and 34 familially retarded children, ages 4-4 to 13-1. The two groups were matched for mental age, socioeconomic status, public school attendance, and intact family structure. Results indicate that familial retardates performed as well as normals and at times surpassed them. Performance on these representational tasks is, predominantly, a function of mental age which lends support to a "developmental" theory of familial retardation and refutes the "defect" hypothesis.     

The effects on induced passive rehearsal and the von Restorff phenomenon on the free recall of normals and retardates

Noninstitutionalized retardates and normal children of equal mental age (approximately 8 years) listened to 11 orders of 20 nouns with no instructions to overtly or covertly rehearse. All subjects were in each of three list conditions: (a) when all words were at the same decibel (dB) level, (b) when the 11th item was at a higher dB level, and (c) when the items were repeated at the same dB level using the rehearsal protocol of Rundus (1971). The normals' overall recall was superior to that of the retardates' recall. Repetition of items had no effect on the performance of either group except in the recency portion of the learning curve and on the initial trial for both groups and the fifth trial for the retarded group. The normal group was more susceptible to the yon Restorff effect than was the retarded group. These results were discussed in terms of the changing and different recall strategies of the two groups.     

Role of CA3 and CA1 subregions of the dorsal hippocampus on temporal processing of objects

Previous research in the dorsal CA1 and dorsal CA3 subregions of the hippocampus has been shown to play an important role in mediating temporal order memory for spatial location information. What is not known is whether the dorsal CA3 and dorsal CA1 subregions of the hippocampus are also involved in temporal order for visual object information. Rats with dorsal CA1, dorsal CA3 or control lesions were tested in a temporal order task for visual objects using an exploratory paradigm. The results indicated that the controls and the dorsal CA3 lesioned rats preferred the first rather then the last object they had explored previously, indicating good memory for temporal order of object presentation. In contrast, rats with dorsal CA1 lesions displayed a profound deficit in remembering the order of the visual object presentations in that they preferred the last object rather than the first. All three groups of rats preferred a novel object compared to a previously explored object suggesting normal detection of visual object novelty. The results suggest that only the dorsal CA1, but not dorsal CA3, region is critical for processing temporal information for visual objects without affecting the detection of new visual objects.     

Recovery from object substitution masking induced by transient suppression of visual motion processing: a repetitive transcranial magnetic stimulation study

Object substitution masking is a form of visual backward masking in which a briefly presented target is rendered invisible by a lingering mask that is too sparse to produce lower image-level interference. Recent studies suggested the importance of an updating process in a higher object-level representation, which should rely on the processing of visual motion, in this masking. Repetitive transcranial magnetic stimulation (rTMS) was used to investigate whether functional suppression of motion processing would selectively reduce substitution masking. rTMS-induced transient functional disruption of cortical area V5/MT+, which is important for motion analysis, or V1, which is reciprocally connected with V5/MT+, produced recovery from masking, whereas sham stimulation did not. Furthermore, masking remained undiminished following rTMS over the region 2 cm posterior to V5/MT+, ruling out nonspecific effects of real stimulation and confirming regional specificity of the rTMS effect. The results suggest that object continuity via the normal function of the visual motion processing system might in part contribute to this masking. The relation of these findings to the reentrant processing view of object substitution masking and other visual phenomena is discussed.     

Effects of spatial separation between stimuli in whole report from brief visual displays

Direct measurements of the effects of spatial separation between stimuli in whole report from brief visual displays are reported. The stimuli were presented on the periphery of an imaginary circle centered on fixation. In Experiment 1, each display showed two capital letters (letter height approximately equal 1.3 degrees, width approximately equal 0.9 degree, eccentricity approximately equal 5.5 degrees). The proportion of correctly reported letters was a strictly increasing, decelerating function of the spatial separation between the letters for center-to-center separations ranging from less than 2 degrees to more than 10 degrees of visual angle. Experiment 2 yielded similar results with triples of letters. Experiment 3 showed that accuracy increased with spatial separation for report of two short words, and Experiment 4 showed the same result for words presented upside down. The results are explained by a model of lateral masking (crowding) based on competitive interactions within receptive fields of cortical neurons.