Impaired tactual perception in children with Down's syndrome

Using standardized neuropsychological tests, tactual finger discrimination, graphaesthesia and stereognosis were studied in a group of 11 children aged 7–11 years with Down's syndrome (DS). All tasks were solved without visual control. The performance was subnormal in each test and the results of the stereognosis test were particularly poor. It was ascertained that the DS children could understand test instructions. Moreover, under visual control all objects used in the stereognosis test were handled correctly. The results suggest that tactual perception is subnormal in children with DS. The pathogenesis of the somatosensory abnormalities should be explored.     

Tactual, visual, and cross-modal transfer of texture in 5- and 8-year-old children

Children's tactual, visual, and cross-modal transfer abilities for texture were investigated in a delayed matching-to-sample paradigm. Transfer performance from vision to touch was found to increase between 5 and 8 years of age, whereas transfer performance from touch to vision did not vary with age and matched touch-to-touch performance. Asymmetrical cross-modal abilities were observed at the age of 8 years, vision-to-touch transfer performance being higher than touch-to-vision transfer performance (experiment 2). This developmental pattern could not be attributed to limitations in the tactual or visual discriminability of the textures or to differences in tactual or visual memory between the two age groups (experiment 1). It is suggested that the increase with age in vision-to-touch performance may be related to the intervention of more efficient top-down perceptual processes in the older children.     

Tactual perception: a review of experimental variables and procedures

This paper reviews the literature on tactual perception. Throughout this review, we will highlight some of the most relevant aspects in the touch literature: type of stimuli; type of participants; type of tactile exploration; and finally, the interaction between touch and other senses. Regarding type of stimuli, we will analyse studies with abstract stimuli such as vibrations, with two- and three-dimensional stimuli, and also concrete stimuli, considering the relation between familiar and unfamiliar stimuli and the haptic perception of faces. Under the "type of participants" topic, we separated studies with blind participants, studies with children and adults, and also performed an overview of sex differences in performance. The type of tactile exploration is explored considering conditions of active and passive touch, the relevance of movement in touch and the relation between haptic exploration and time. Finally, interactions between touch and vision, touch and smell and touch and taste are explored in the last topic. The review ends with an overall conclusion on the state of the art for the tactual perception literature. With this work, we intend to present an organised overview of the main variables in touch experiments, compiling aspects reported in the tactual literature, and attempting to provide both a summary of previous findings, and a guide to the design of future works on tactual perception and memory, through a presentation of implications from previous studies.     

Symmetry in haptic and in visual shape perception

Four experiments tested the hypothesis that bilateral symmetry is an incidental encoding property in vision, but can also be elicited as an incidental effect in touch, provided that sufficient spatial reference information is available initially for haptic inputs to be organized spatially. Experiment 1 showed that symmetry facilitated processing in vision, even though the task required judgments of stimulus closure rather than the detection of symmetry. The same task and stimuli failed to show symmetry effects in tactual scanning by one finger (Experiment 2). Experiment 3 found facilitating effects for vertically symmetric open stimuli, although not for closed patterns, in two-forefinger exploration when the fore-fingers had previously been aligned to the body midaxis to provide body-centered spatial reference. The one-finger exploration condition again failed to show symmetry effects. Experiment 4 replicated the facilitating effects of symmetry for open symmetric shapes in tactual exploration by the two (previously aligned) forefingers. Closed shapes again showed no effect. Spatial-reference information, finger movements, and stimulus factors in shape perception by touch are discussed.     

Similarity of tactual and visual picture recognition with limited field of view.

Subjects attempted to recognize simple line drawings of common objects using either touch or vision. In the touch condition, subjects explored raised line drawings using the distal pad of the index finger or the distal pads both of the index and of the middle fingers. In the visual condition, a computer-driven display was used to simulate tactual exploration. By moving an electronic pen over a digitizing tablet, the subject could explore a line drawing stored in memory; on the display screen a portion of the drawing appeared to move behind a stationary aperture, in concert with the movement of the pen. This aperture was varied in width, thus simulating the use of one or two fingers. In terms of average recognition accuracy and average response latency, recognition performance was virtually the same in the one-finger touch condition and the simulated one-finger vision condition. Visual recognition performance improved considerably when the visual field size was doubled (simulating two fingers), but tactual performance showed little improvement, suggesting that the effective tactual field of view for this task is approximately equal to one finger pad. This latter result agrees with other reports in the literature indicating that integration of two-dimensional pattern information extending over multiple fingers on the same hand is quite poor. The near equivalence of tactual picture perception and narrow-field vision suggests that the difficulties of tactual picture recognition must be largely due to the narrowness of the effective field of view.     

Hand-movement profiles in a tactual—tactual matching task: Effects of spatial factors and laterality

We examined the effect of spatial factors and hemispheric lateralization upon hand-scanning strategies in 14 right-handed men tested in a tactual—tactual matching task. The experiment involved comparisons (judgments of same or different) between two objects sequentially touched by the fingertips of the left or right hand. Stimuli were made of smoothly joined cubes whose junctions were not haptically discernible. Exploratory strategies were inferred from the durations and locations of hand contacts with any of the cubes composing the stimuli. Accuracy was greater when the same stimulus was touched twice by the same hand than when different hands were used to feel it. With regard to strategies, both hands touched the upper parts of the object longer than the lower parts. Subjects also inspected more portions of the objects ipsilateral to the hand used. Overall differences in time spent touching cubes were greater for the right hand than for the left hand, showing that touch times were less evenly distributed on object parts for the former than for the latter. In this study, the process of information gathering by touch appears to be determined by the intertwining integration of contextual factors (e.g., stimulus position in space), biomechanical constraints on hand movements, and such cognitive factors as hemispheric differences on the ability to encode spatial pattern information.     

Perceived age and sex characteristics of voices of institutionalized children with Down's syndrome.

It was hypothesized that the voices of children with Down's syndrome would be perceived as younger than their true chronological age and that perceptual auditors would have considerable difficulty in identifying the correct sex of these children by voice alone. Perceived age and sex were investigated in 20 institutional children with Down's syndrome who were matched for sex and age with a control group of 20 normal children. Randomized matched verbal samples were played backwards to a group of 16 listener/judges who rated the samples as to age and sex. The results indicated that the voices of these Down syndrome children were perceived as being more than 2 yr. younger than their group mean age and that there was a negative correlation between the biological sex of such children and their perceived sex.     

Tactual learning and cross-modal transfer of an oddity problem in young children

The ability to solve tactual oddity problems, and transfer of oddity learning across the visual and the tactual modalities, was studied in 3- to 8-year-old children (N = 294). Oddity tasks consisting of one odd and two equal objects were made from stimuli that were easily discriminated visually and tactually. The results showed that tactual oddity learning increased gradually with age. The growth in tactual performance begins later than visual, suggesting that children are more adept at encoding visual stimulus invariances or relational properties than tactual ones. Bidirectional cross-modal transfer of oddity learning was found, supporting the suggestion that such transfer occurs when training and transfer oddity tasks share a common vehicle dimension. The cross-modal effect also shows that oddity learning is independent of a specific modality-labeled perceptual context. Our results are consistent with the view that development of oddity learning depends on a single rather than a dual process, and that the oddity relation may be treated as an amodal stimulus feature.     

Children's voluntary exploration and preference for tactually presented nonsense shapes differing in complexity

This study represents an extension of research on children's response to nonsense shapes varying in complexity to the tactual modality. Wooden cut-out shapes varying in number of turns from 3 to 40 were presented to children at Grades I, III, and VI, both for voluntary haptic exploration, and for preference choices. Both of these measures yielded monotonically increasing functions in the oldest group, while the youngest showed a similar but much flatter gradient for exploration times, and an inverted-U shaped preference function; data for the Third Grade subjects were in both cases intermediate. Supplementary data based on an analysis of preference choice latencies for stimulus pairs of adjacent levels of complexity, as well as on ratings of subject's mode of exploration of the stimuli under both response sets showed a marked shift from a predominantly passive to an increasingly active mode of exploration. These results are related to the age differences for the exploration-time and preference data, and discussed in relation to Schachtel's differentiation between allocentric and autocentric modes of perception.     

Vision for perception and vision for action: normal and unusual development

Evidence suggests that visual processing is divided into the dorsal ('how') and ventral ('what') streams. We examined the normal development of these streams and their breakdown under neurological deficit by comparing performance of normally developing children and Williams syndrome individuals on two tasks: a visually guided action ('how') task, in which participants posted a card into an oriented slot, and a perception ('what') task, in which they matched a card to the slot's orientation. Results showed that all groups performed worse on the action task than the perception task, but the disparity was more pronounced in WS individuals and in normal 3-4-year-olds than in older children. These findings suggest that the 'how' system may be relatively slow to develop and more vulnerable to breakdown than the 'what' system.     

Effects of tactual and phonological similarity on the recall of Braille letters by blind children.

Forty-eight severly blind children, able to cope with set-sizes of two and three, four, five or six serial items were tested on probed recall of Braille letters they could either name or discriminate, when the letters were (1) dissimilar in tactual characteristics and name sounds, (2) similar in feel, but different in name sound, and (3) dissimilar in feel but similar in name sound. Results showed that tactual similarity produced recall decrements by subjects able to be tested under set-sizes of up to five items, while phonological similarity produced recall decrements by subjects testable under set-sizes of five and six items. It was argued that tactual information survives perception and affects recall, and that blind children can encode tactual inputs either tactually or verbally, but that this probably depends upon different processes.     

Touch,awareness of touch,and compliance with a request

In certain situations it has been shown that touch has a positive effect on the compliance with a request expressed by a stranger. However, the difference between the effect of touch on request compliance between people who had noticed and those who had not noticed this contact has never been taken into account. In this experiment a female confederate asked 227 women to answer a questionnaire. When asking for their collaboration the forearm was or was not touched for a brief period of 1 to 2 seconds. Analysis showed that touch was associated with significantly higher compliance to the request but no difference was found between subjects who had noticed the tactual contact and subjects who had not noticed.     

Development of lateral asymmetry in the perception of sequentially touched fingers

In order to investigate lateral asymmetry in tactile perception, two or four fingers of normal primary school children were touched sequentially. Stimulation was either unimanual or bimanual and either verbal or nonverbal responses were required. Right hand advantage was demonstrated subsequent to uni- and bimanual stimulation in both the verbal and nonverbal response conditions. Neither an age nor a sex effect on laterality was found. Right hand advantage was affected by direction of stimulation in the bimanual condition. Left hemispheric dominance was argued to be related to the temporal nature of the tasks.     

Can shape be perceived by dynamic touch?

The possibility that some aspects of the shapes of solid objects can be perceived through dynamic touch, even when the objects are not touched, but simply wielded with a handle, was investigated in four experiments. Wooden solids were constructed of three sizes and five shapes: hemisphere, cylinder, parallelepiped, cone, and pyramid. Experiments 1 and 2 involved comparisons (judgments of same or different) between and among wielded objects of the same mass. In Experiments 3 and 4, subjects were required to wield an object and to select a match from a visible arrangement of objects of the five shapes; the wielded objects were of two sizes, each different from that of the visible objects. The success of subjects at these tasks, and the patternings of errors, are seen to involve the characteristic moment of inertia profiles of each shape, and a ratio of the object's resistances to rotation around orthogonal axes is shown to be a strong predictor of performance in the identification experiments. The results are discussed with reference to dynamic touch and to the notion of shape invariants that do not reduce to aspects of object surface.     

Étude du style interactif maternel et des compétences sociocommunicatives des enfants. Une étude comparative entre enfants porteurs de trisomie et enfants typiques

The goal is to explain Down syndrome social language disturbances. Down's syndrome and non-handicapped children were observed interacting with their mothers. We compared 22 dyads with Down syndrome children and 22 dyads with non-handicapped children. Down's syndrome children were matched on mental age with non-handicapped children (4 to 24 months). Social context, mothers' behaviours and children's social communicative competences were evaluated. Interaction behaviours in the mothers of DS children differ from those of mothers of non-handicapped children. DS communicative competences also are different from those in non-handicapped children. We argue that mothers' behavioural interaction in the dyads with DS children can be an aspect of social communicative disturbances of DS children.     

Children's understanding of natural language hierarchies

Three experiments examined young children's ability to evaluate the relationship between concepts as one of inclusion. In Experiment 1, the same group of 4-to 7-year-old children were given three tasks: one in which they made judgments about whether “all” or “some” members of a category were included in another category, and two tasks in which they made inferences based on knowledge of inclusion relations. The majority of children succeeded on at least one of the tasks, thereby implying that they could evaluate inclusion relations. Two further experiments provided more evidence for this hypothesis: Experiment 2 confirmed that nursery children could answer quantitative questions about conceptual interrelationts; Experiment 3 demonstrated that nursery schoolers could solve certain inference problems involving the construction and evaluation of hierarchies.     

Infinite utility: Anonymity and person-centredness

This paper addresses the nature of touch or ‘tactual perception’. I argue that touch encompasses a wide range of perceptual achievements, that treating it as a number of separate senses will not work, and that the permissive conception we are left with is so permissive that it is unclear how touch might be distinguished from the other senses. I conclude that no criteria will succeed in individuating touch. Although I do not rule out the possibility that this also applies to other senses, I suggest that the heterogeneity of touch makes it both distinctive and particularly problematic.     

Effect of scaling method on perception of textiles

This study examined the effect of scaling methods on tactual ratings of fabrics. Four tactile attributes, namely, stiffness, thickness, roughness, and warmth, of 11 test fabrics with a wide variety of tactual qualities were evaluated by 75 college students enrolled in textile courses. The tactual ratings of all four attributes evaluated by touch and sight and touch were significantly correlated. The tactual evaluation made on a 7-point semantic differential scale on each test fabric was compared with tactual ranking by paired-comparison method. Significant correlations were found between two rankings of four attributes.     

Visual and tactual texture perception: Intersensory cooperation

In three experiments, subjects were required to make texture judgments about abrasive surfaces. Touch and vision provided comparable levels of performance when observers attempted to select the smoothest of three surfaces, but bimodal visual and tactual input led to greater accuracy. The superiority of bimodal perception was ascribed to visual guidance of tactual exploration. The elimination of visual texture cues did not impair bimodal performance if vision of hand movements were permitted. It is suggested that touch may preempt vision when both sources of texture information are simultaneously available. The results support the notion that perception is normally multimodal, since restriction of the observer to either sense in isolation produces lower levels of performance.     

The Sense of Touch: From Tactility to Tactual Probing

Because philosophical reflections on touch usually start from our ability to perceive properties of objects, they tend to overlook features of touch that are crucial to correct understanding of tactual perception. This paper brings out these features and uses them to develop a general reconception of the sense of touch. I start by taking a fresh look at our ability to feel, in order to reveal its vital role. This sheds a different light on the skin's perceptual potential. While it is commonly observed that tactile experiences have two intentional objects, an external object and one's own body, I will advance a more accurate alternative: in tactile experiences, one becomes aware of what one's body undergoes. This alternative not only fits better with tactility's vital role; it is also key to explaining how active touching provides for a unique contribution to our perceptual relation to material objects. By thus connecting tactility's vital role to the way we rely on touch while manipulating objects, this essay offers a cross-sectional survey of our tactile powers that reveals the interplay between sensing and touching.