Modality-specific spatial coordinates

Spatial Task Performance: A Meta-Analysis

The literature which compared spatial task performance of blind and sighted subjects was analyzed using a meta-analytic approach. Effect sizes were computed for comparisons between early versus late onset visually impaired subjects, early onset versus sighted, late onset versus sighted, and mixed onset versus sighted. The results are based on 47 studies that analyzed the spatial task performance of 1,289 sighted subjects, 691 early onset subjects, 183 late onset, and 657 mixed onset. The early onset group generally showed poorer performance in comparisons with either the late onset or the sighted groups. Comparisons involving the mixed onset group showed inconsistent results. This finding is discussed in light of the need to more exactly specify the variable of age of onset. The findings from this study synthesize the past research efforts in this field. Suggestions for a future research agenda include a shift toward examining within group differences among visually impaired persons.

Models of Sensory Deprivation: The Nature/Nurture Dichotomy and Spatial Representation in the Blind

It is argued that models of sensory deprivation often depend on a nativist versus empiricist dichotomy which has little basis in empirical fact. Fallacies about the nature of abilities and learning and about the interaction between sense modalities which follow from the dichotomy are examined in relation to explanations of spatial development in the blind. It is suggested that interactions between cognitive and perceptual factors need to be taken into account in order to explain the effects of sensory deprivation more adequately.

Hand preferences and hand ability in congenitally blind children

Congenitally blind and sighted blindfolded children between the ages of 6 and 14 years were tested for hand preference with performance tasks. There were no differences between the groups in direction or degree of hand preference. The degree of handedness increased with age and was essentially linear though the blind seemed to be somewhat less lateralized at the younger ages. When the same groups were required to match three-dimensional bricks for height, depth, breadth, and volume, no hand advantages were found for either group. Both groups of children improved in their accuracy of spatial discriminations with age. Further, the degree of lateralization on the handedness task did not relate to ability on the tactile task or to differences between the right and left hands on the tactile task. Thus, there is no effect of blindness on tactile matching ability nor is there an effect of the hand used in the task.

Mental rotation of tactual stimuli

Three experiments involving different angular orientations of tactual shapes were performed. In experiment 1 subjects were timed as they made 'same-different' judgments about two successive rotated shapes. Results showed that no rotation effect is obtained, i.e., reaction times and error percentage do not increase linearly with rotation angle. The same negative results were found in experiment 2, in which subjects were similarly timed while they made mirror-image discriminations. In experiment 3 a single-stimulus paradigm was used and subjects were asked to decide if a rotated stimulus was a 'normal' or 'reversed' version. Reaction times increased linearly with angular departure from the vertical. Therefore, for tactual stimuli too, this study confirms previous results, which suggest that a mental rotation strategy only occurs if it is facilitated by both type of task and type of stimulus. Results also show a significant difference between hands, and between hands and type of response. Implied hemispheric differences are discussed.

Tactile memory in sighted and blind observers: the influence of orientation and rate of presentation

Sighted, early blind, and late blind subjects attempted to identify numerals or number sequences printed on their palms. The numerals were either upright, or inverted, or rotated perpendicular to the arm axis. Stimulus rotation degraded recognition in the early blind subjects, suggesting the influence of experience with visual frames of reference. Slower rates of presentation with upright number sequences improved recall in both sighted and blind observers. An experiment on tactual-visual braille recognition in the sighted observers showed that tilt degraded pattern identification, but visual guidance of the fingertip and ballpoint minimized this loss. A further experiment was performed to distinguish between visual imagery and visual frame of reference explanations of the visual guidance effect on recognition of rotated braille. Subjects explored upright or tilted braille characters while viewing only a light emitting diode on the exploratory fingertip. Sight of scanning movements did not aid pattern recognition with tilt. The results indicate that the benefits of visual guidance on recognition of tilted patterns were probably due to frame of reference information. It is concluded that spatial reference information may aid tactile memory in the sighted and late blind, since the early blind performed at a lower level in the retention task. It is proposed that visual imagery may only explain the superiority of the sighted and late blind when familiar stimuli are studied.

Eliminating the haptic oblique effect: influence of scanning incongruity and prior knowledge of the standards

Although the oblique effect has been conceptualized as a purely visual phenomenon, recent studies report its occurrence in a haptic matching task and present the hypothesis that differences in haptic orientational sensitivity might be responsible for the results. The possibility that procedural variables could be responsible was investigated. Specifically, the effect of prior knowledge of the stimulus orientation standards and of use of bilateral haptic exploration of standard and comparison orientations was examined. The results indicate that the reported oblique effect is reduced either when subjects are not informed which orientations will be tested, or when a unilateral matching procedure instead of a bilateral one is used. When both conditions are combined, the haptic oblique effect is eliminated. It is concluded that this particular manifestation of the oblique effect is not related to haptic sensitivity, but stems from the use of well-established imagery as referent for a match (imagery for oblique stimulus orientations is inferior) and the inherently different scanning patterns required in bilateral exploration of obliques (percepts of standard and comparison obliques will be necessarily different).

Effect of modality-specific experience on visual and haptic judgment of orientation

Although the 'oblique effect' (poorer performance on oblique orientations as compared to performance on vertical and horizontal orientations) is generally understood as a strictly visual phenomenon, a haptic oblique effect occurs for blindfolded subjects required to set a stimulus rod by hand. Because oblique effects are often attributed to the observer's experience with a predominantly horizontal and vertical environment, we assessed the effect of visual and haptic experience by providing subjects with modality-specific inspection periods to familiarize them with the more poorly judged obliques. Oblique error was significantly reduced in magnitude for judgments made by the modality of experience, and for judgments made across modalities. Rate of improvement, consistency of transfer, and the subjective reports of subjects indicate that this haptic oblique effect is more strongly influenced by visual experience and imagery than by haptic experience. It need not be interpreted as an effect based on factors intrinsic to the haptic modality.

Movement cues and body orientation in recall of locations by blind and sighted children

Experiment 1 tested blind children's recall of locations with repeated and changed recall movements under normal and out-of-line body-to-target orientation. Changed movements produced target undershooting and inaccurate path-keeping by the older blind, particularly for horizontal directions. Errors by the younger blind depended more on body orientation.

Experiment 2 tested blindfolded sighted children under the same conditions, with four forms of coding instructions. The sighted showed no effect of body orientation, but changed movements had similar effects on target localization as for the older blind, regardless of instructions. Different forms of instructions affected bias from movement directions in near and far sectors of the display differently, and instructions to code by reference to the shape of the display surround eliminated the differences.

It was argued that blind and sighted children use extent and direction cues from the positioning movement in locating targets, and that these are not automatic effects but result from children's assessment of the informational conditions.

An islet of ability in autistic children: a research note

An aspect of cognitive functioning in autistic children was investigated by comparing their performance on the Children's Embedded Figures Test with that of MA-matched normal and MA- and CA-matched mentally retarded non-autistic children. The autistic children were significantly more competent at this task than either group of control children, and also showed qualitatively different strategies. Since the performance of the autistic children was better than predicted from MA and commensurate with CA, it can be regarded as an islet of ability. This finding is discussed in terms of orientation and visualization factors involved in visuo-spatial abilities and is also related to cognitive deficit.

Self-referent and movement cues in coding spatial location by blind and sighted children

The study tested the hypothesis that movement and self-referent information differ, and that children can use both to code unseen locations. In one experiment blindfolded sighted children made more errors with changed than with unchanged accessing movements, despite unchanged reference conditions. Rotation decreased accuracy further, although most responses were to the correct side. Age did not interact with experimental conditions. In another experiment blind children and matched blindfolded controls were less accurate with changed movements; and rotations were more difficult still. Visual experience, but not age, interacted with conditions. The blind showed significantly more self-reference (responses to the original side in rotations), and were somewhat worse also with changed movements alone but did not differ from controls when movements and references were unchanged. The results support the hypothesis that movement and self-referent information differ. Visuospatial experience and task conditions rather than age seem to determine the extent to which children use either form of information.

The utilization of external and movement cues in simple spatial tasks by blind and sighted children

The role of visual experience in coding spatial position by movements or by external cues was examined in simple (nonrotational) shift tasks with blind and sighted children. Age and the salience of external cues were also of interest. Results showed that the congenitally totally blind used movement cues significantly more even when external cues were present and prominent. The blind with minimal visual experience coded by external cues, but made errors beyond the age by which blindfolded sighted children performed correctly. It was argued that visual experience affects coding by drawing attention to external cues, and by providing more adequate spatial information than other sources usually available to the blind. In its absence, movement coding and self-reference can become preferred strategies.

Methods of assessment for use with the visually and mentally handicapped: a selective review

Literature published during the last 15 years and concerning assessment techniques applicable to the visually and mentally handicapped is reviewed. Aspects of assessment considered include professional organisation of health teams, electrophysiological measures, psychometric methods and some experimental investigations. The value of more reliable behavioural observation relevant to the client's future practical training needs is stressed.

Location and distance estimates by blind and sighted children

Blindfold normal, blindfold autistic and congenitally blind children made reproduction location and distance estimates of an arm movement. For each task they first experienced a standard vertical movement of a predetermined extent. In the test tasks which followed, they either reproduced the movement exactly, reproduced the end point although commencing from a different starting position, or reproduced the same distance from a different starting point. Sighted normal children and blind children performed very similarly on both the reproduction and the location task. However on distance reproduction, the blind children underestimated the longer distances more markedly than did the normals. Autistic children resembled the blind in their attempts to reproduce the longer distances. In addition they had a tendency to overshoot over short distances in all tasks.

The results are discussed in terms of the role of a visual reference system for different aspects of motor movements.