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.     

Imagery in the congenitally blind: how visual are visual images?

Three experiments compared congenitally blind and sighted adults and children on tasks presumed to involve visual imagery in memory. In all three, the blind subjects' performances were remarkably similar to the sighted. The first two experiments examined Paivio's (1971) modality-specific imagery hypothesis. Experiment 1 used a paired-associate task with words whose referents were high in either visual or auditory imagery. The blind, like the sighted, recalled more high-visual-imagery pairs than any others. Experiment 2 used a free-recall task for words grouped according to modality-specific attributes, such as color and sound. The blind performed as well as the sighted on words grouped by color. In fact, the only consistent deficit in both experiments occurred for the sighted in recall of words whose referents are primarily auditory. These results challenge Paivio's theory and suggest either (a) that the visual imagery used by the sighted is no more facilitating than the abstract semantic representations used by the blind or (b) that the sighted are not using visual imagery. Experiment 3 used Neisser and Kerr's (1973) imaging task. Subjects formed images of scenes in which target objects were described as either visible in the picture plane or concealed by another object and thus not visible. On an incidental recall test for the target objects, the blind, like the sighted, recalled more pictorial than concealed targets. This finding suggests that the haptic images of the blind maintain occlusion just as the visual images of the sighted do.     

盲人的时间水平方向隐喻的通道特异性

通过2个实验, 考察了感觉通道对盲人的时间水平方向隐喻的影响。实验1发现, 盲人只在动作水平上存在同阅读方向一致的时间水平方向隐喻, 对表征过去的词或句子按左键反应和对表征将来的词或句子按右键反应时更快, 表明盲人用于隐喻时间的空间信息是知觉性的。实验2比较了明眼人可视组被试和明眼人遮眼组被试的时间空间隐喻, 发现明眼人可视组被试只在动作水平上存在时间水平方向隐喻, 明眼人遮眼组被试只在刺激在右侧时呈现才出现动作水平的时间水平方向隐喻。综合分析表明, 盲人和明眼人可视组被试的反应更为接近, 表明盲人的时间空间隐喻未受听觉信息的影响。盲人通过运动通道获得的空间认知代偿了视觉通道信息的缺失。     

The haptic oblique effect in the perception of rod orientation by blind adults

The haptic perception of vertical, horizontal, +45° oblique, and +135° oblique orientations was studied in completely blind adults. The purpose was to determine whether the variations of the gravitational cues provided by the arm-hand system during scanning would affect the manifestation of the oblique effect (lower performance in oblique orientations than in vertical-horizontal ones) as they did in blindfolded sighted people (Gentaz & Hatwell, 1996). In blindfolded sighted adults, the oblique effect was reduced or absent when the magnitude of gravitational cues was decreased. If visual experience participated in the haptic oblique effect, we should observe no oblique effect in early blind subjects in the conditions of manual exploration where late blind and blindfolded sighted manifest this effect. The magnitude of gravitational cues was therefore varied by changing gravity constraints, whereas the variability of these cues was varied by changing the plane in which the task was performed: horizontal (low variability) and frontal (high variability). Early and late blind adults were asked to explore haptically a rod and then to reproduce its orientation ipsilateraUy in one of two exploratory conditions in each plane. In the horizontal plane, the oblique effect was absent, whatever the gravity constraints, in both groups (early and late blind subjects). In the frontal plane, the oblique effect was present, whatever the gravity constraints, in both groups. Taken together, these results showed that, in blind people, the variability of gravitational cues played a role in the haptic oblique effect; no effect of previous visual experience was observed.     

Tactile perception in blind Braille readers: a psychophysical study of acuity and hyperacuity using gratings and dot patterns

It is not clear whether the blind are generally superior to the sighted on measures of tactile sensitivity or whether they excel only on certain tests owing to the specifics of their tactile experience. We compared the discrimination performance of blind Braille readers and age-matched sighted subjects on three tactile tasks using precisely specified stimuli. Initially, the blind significantly outperformed the sighted at a hyperacuity task using Braille-like dot patterns, although, with practice, both groups performed equally well. On two other tasks, hyperacute discrimination of gratings that differed in ridge width and spatial-acuity-dependent discrimination of grating orientation, the performance of the blind did not differ significantly from that of sighted subjects. These results probably reflect the specificity of perceptual learning due to Braille-reading experience.     

Conservation by the congenitally blind

A conservation study of amount using specially designed wire cylinders was made of congenitally blind children and two control groups of sighted children (one of which undertook the task blindfolded), matched for chronological age. No differences were found among the three groups on the age of attainment of conservation. However, the manner by which the blind processed the environment differed from the blindfolded sighted children, as evidenced in some of their non-conservation answers. The language of the blind children did not differ from that of the sighted children in describing the materials, but the language of the non-conserving children of all groups differed from that of conserving children. The importance for several theoretical views on the attainment of conservation is discussed, and it is argued that the achievement of the beginning of operational thinking may be more a central developmental phenomenon than one based on specific sensory experience.     

Effect of visual experience on iocational judgements after perspective change in small-scale space

Congenitally blind, late blind and blindfold sighted adults overleamed an object-array within a square frame by touch, and judged, facing the midpoint of the frame, the near/far/left/right locations of objects from sides and diagonally from corners. One-half were first guided to points (A-condition), the rest were first asked to imagine themselves as being at points (I-condition). Group and condition did not, but group and observation point did, interact. Lack of visual experience added to RTs and total times and increased errors especially at diagonal stations. Congenitally blind subjects differed from both late blind and blindfold sighted subjects. However, a section of the congenitally blind subjects attained the level of blindfold sighted subjects. The sequence A-I speeded up judgements in all groups. Group did not interact with size of space. Congenitally blind subjects reportedly resorted to holistic representations, but had specific limitations in using them at diagonal stations. Orientation skills of the congenitally blind in far space could be improved by practising perspective taking in near space.     

The role of visual experience on the representation and updating of novel haptic scenes

We investigated the role of visual experience on the spatial representation and updating of haptic scenes by comparing recognition performance across sighted, congenitally and late blind participants. We first established that spatial updating occurs in sighted individuals to haptic scenes of novel objects. All participants were required to recognise a previously learned haptic scene of novel objects presented across the same or different orientation as learning whilst they either remained in the same position to moved to a new position relative to the scene. Scene rotation incurred a cost in recognition performance in all groups. However, overall haptic scene recognition performance was worse in the congenitally blind group. Moreover, unlike the late blind or sighted groups, the congenitally blind group were unable to compensate for the cost in scene rotation with observer motion. Our results suggest that vision plays an important role in representing and updating spatial information encoded through touch and have important implications for the role of vision in the development of neuronal areas involved in spatial cognition.     

Memory processing of spatial order as transmitted by auditory information in the absence of visual cues

Two experiments were conducted concerning spatial order recall when spatial information is transmitted by auditory stimuli. Temporal order either was congruent with spatial order or was independent of spatial order. In Experiment 1, the comparisons were among normally or partially sighted subjects allowed to look, normally sighted subjects who were blindfolded, and blind children. The main findings were a superiority of the sighted subjects allowed to look (that is, to support auditory information with visual cues) and a smaller advantage for the sighted-but-blindfolded subjects, relative to the blind group. In Experiment 2, normally sighted adults (either seeing or blindfolded) and blind adults were tested. Surprisingly, the blind were not worse than the sighted in this study. Subsequent interviews and detailed analysis of errors suggested that the blind coded spatial information kinesthetically. These indirect analyses also suggested that whereas spatial order was coded temporally in the sighted, it was controlled by both temporal and spatial factors in the blind and blindfolded subjects.     

Mental rotation and the frame of reference in blind and sighted individuals

Mental rotation in the congenitally blind was investigated with a haptic letter-judgment task. Blind subjects and blindfolded, sighted subjects were presented a letter in some orientation between 0° to 300° from upright and timed while they judged whether it was a normal or mirror-image letter. Both groups showed an increasing response time with the stimulus’s departure from upright; this result was interpreted as reflecting the process of mental rotation. The results for the blind subjects suggest that mental rotation can operate on a spatial representation that does not have any specifically visual components. Further research showed that for the sighted subjects in the haptic task, the orientation of a letter is coded with respect to the position of the hand. Sighted subjects may code the orientation of the letter and then translate this code into a visual representation, or they may use a spatial representation that is not specifically visual.     

Cognitive representation of auditory space in blind football experts

ObjectivesWe compared the mental representation of sound directions in blind football players, blind non-athletes and sighted individuals.DesignStanding blindfolded in the middle of a circle with 16 loudspeakers, participants judged whether the directions of two subsequently presented sounds were similar or not.MethodStructure dimensional analysis (SDA) was applied to reveal mean cluster solutions for the groups.ResultsHierarchical cluster analysis via SDA resulted in distinct representation structures of sound directions. The blind football players' mean cluster solution consisted of pairs of neighboring directions. The blind non-athletes also clustered the directions in pairs, but included non-adjacent directions. In the sighted participants' structure, frontal directions were clustered pairwise, the absolute back was singled out, and the side regions accounted for more directions.ConclusionsOur results suggest that the mental representation of egocentric auditory space is influenced by sight and by the level of expertise in auditory-based orientation and navigation.     

Blind children recognizing tactile pictures respond like sighted children given guidance in exploration

Theory of tactile pictures argues that untrained blind subjects can recognize raised, outline pictures. It contends the blind person’s knowledge of the shapes of common objects is like that of the sighted, and the blind person’s pictorial abilities use the same principles as the sighted person’s. To test this theory, blind children (aged 8–13) and blindfolded age-matched sighted children were asked to identify raised-line drawings of common objects. Their performances were correlated. In addition, the blind children identified more than sighted children exploring the pictures actively, but the same number of pictures as sighted children who were given passive, guided exploration. We argue blind and sighted children use the same principles to identify the pictures, but the blind have superior exploration skills. The differences in the effects of exploration skills on recognition scores are minimized when the sighted children are given guidance, since the sighted children then have efficient contact with the displays, and the performance of the sighted and the blind is then governed by the same principles, without one group benefitting from advantages in exploration skills.     

Structural properties of spatial representations in blind people: Scanning images constructed from haptic exploration or from locomotion in a 3-D audio virtual environment

When people scan mental images, their response times increase linearly with increases in the distance to be scanned, which is generally taken as reflecting the fact that their internal representations incorporate the metric properties of the corresponding objects. In view of this finding, we investigated the structural properties of spatial mental images created from nonvisual sources in three groups (blindfolded sighted, late blind, and congenitally blind). In Experiment 1, blindfolded sighted and late blind participants created metrically accurate spatial representations of a small-scale spatial configuration under both verbal and haptic learning conditions. In Experiment 2, late and congenitally blind participants generated accurate spatial mental images after both verbal and locomotor learning of a full-scale navigable space (created by an immersive audio virtual reality system), whereas blindfolded sighted participants were selectively impaired in their ability to generate precise spatial representations from locomotor experience. These results attest that in the context of a permanent lack of sight, encoding spatial information on the basis of the most reliable currently functional system (the sensorimotor system) is crucial for building a metrically accurate representation of a spatial environment. The results also highlight the potential of spatialized audio-rendering technology for exploring the spatial representations of visually impaired participants.     

Superior haptic perceptual selectivity in late-blind and very-low-vision subjects

Blindfolded sighted, congenitally blind, late-blind, and very-low-vision subjects were tested on a tangible version of the embedded-figures test. The results of ANOVAs on accuracy measures yielded superior performance by the very-low-vision and late-blind subjects compared with the blindfolded sighted and congenitally blind participants. Accuracy of the congenitally blind subjects was similar to that of the blindfolded sighted participants. However, all groups of blind subjects were significantly faster than the blindfolded sighted subjects. It is suggested that experience with pictures combined with haptic skill aid perceptual selectivity in touch.     

Picture and pattern perception in the sighted and the blind: the advantage of the late blind

Two experiments are reported on the contribution of visual experience to tactile perception. In the first experiment, sighted, congenitally blind, and late blind individuals made tactual matches to tangible embossed shapes. In the second experiment, the same subjects attempted tactile identification of raised-line drawings. The three groups did not differ in the accuracy of shape matching, but both groups of blind subjects were much faster than the sighted. Late blind observers were far better than the sighted or congenitally blind at tactile picture identification. Four of the twelve pictures were correctly identified by most of the late blind subjects. The sighted and congenitally blind performed at comparable levels in picture naming. There was no evidence that visual experience alone aided the sighted in the tactile task under investigation, since they performed no better than did the early blind. The superiority of the late blind suggests that visual exposure to drawings and the rules of pictorial representation may help tactile picture identification when combined with a history of tactual experience.     

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.     

Mechanisms in the haptic horizontal-vertical illusion: Evidence from sighted and blind subjects

The haptic horizontal-vertical illusion was studied in two experiments. In Experiment 1, the illusion was relatively weak in sighted subjects and depended on stimulus size and the nature of the figure, that is, whether the pattern was an inverted-T or L shape. Experiment 2 compared early blind and late blind subjects. The illusion was present for an inverted-T figure but absent for an L figure in late blind subjects. However, the early blind subjects treated both the L and T figures as similar and showed the illusion to both. These results support the idea that visual experience may alter haptic judgments in sighted and late blind subjects.     

Haptic orientation perception benefits from visual experience: evidence from early-blind, late-blind, and sighted people

Early-blind, late-blind, and blindfolded sighted participants were presented with two haptic allocentric spatial tasks: a parallel-setting task, in an immediate and a 10-sec delay condition, and a task in which the orientation of a single bar was judged verbally. With respect to deviation size, the data suggest that mental visual processing filled a beneficial role in both tasks. In the parallel-setting task, the early blind performed more variably and showed no improvement with delay, whereas the late blind did improve, but less than the sighted did. In the verbal judgment task, both early- and late-blind participants displayed larger deviations than the sighted controls. Differences between the groups were absent or much weaker with respect to the haptic oblique effect, a finding that reinforces the view that this effect is not of visual origin. The role of visual processing mechanisms and visual experience in haptic spatial tasks is discussed.     

Texture perception in sighted and blind observers

The purpose of the present study was to evaluate the utility of visual imagery for texture perception. In Experiment 1, sighted, early-blind, and late-blind observers made relative smoothness judgments of abrasive surfaces using active or passive tough. In Experiment 2, subjects compared vision and touch in the accuracy of smoothness detection, using a broad range of textures, including very fine surfaces. No differences appeared between the sighted and the blind, and it did not matter if touch were active or passive. Vision and touch showed similar performance with relatively coarse textures, but touch was superior to vision for much finer surface textures. The results were consistent with the notion that visual coding of tactual stimuli is not advantageous (or necessary) for texture perception, since touch may hold advantages for the detection of the smoothness of surfaces.     

Viewpoint and orientation influence picture recognition in the blind

In the first three experiments, subjects felt solid geometrical forms and matched raised-line pictures to the objects. Performance was best in experiment 1 for top views, with shorter response latencies than for side views, front views, or 3-D views with foreshortening. In a second experiment with blind participants, matching accuracy was not significantly affected by prior visual experience, but speed advantages were found for top views, with 3-D views also yielding better matching accuracy than side views. There were no performance advantages for pictures of objects with a constant cross section in the vertical axis. The early-blind participants had lower performance for side and frontal views. The objects were rotated to oblique orientations in experiment 3. Early-blind subjects performed worse than the other subjects given object rotation. Visual experience with pictures of objects at many angles could facilitate identification at oblique orientations. In experiment 5 with blindfolded sighted subjects, tangible pictures were used as targets and as choices. The results yielded superior overall performance for 3-D views (mean, M = 74% correct) and much lower matching accuracy for top views as targets (M = 58% correct). Performance was highest when the target and matching viewpoint were identical, but 3-D views (M = 96% correct) were still far better than top views. The accuracy advantage of the top views also disappeared when more complex objects were tested in experiment 6. Alternative theoretical implications of the results are discussed.