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S J Lederman

Publications and source records attributed to S J Lederman.

At least 37 records · Page 2Linked to original sources
PubMed1993

Cognitive representations of functional interactions with objects.

Two studies addressed people's knowledge about the movements underlying functional interactions with objects, when the interactions were described by simple verbal labels expressing environmental goals. In Experiment 1, subjects rated each action with respect to six dimensions: which portion of the limb moved, distance moved, forcefulness, effectors involved, size of the contact surface, and resemblance to grasp. Ratings were systematic and fell on two distinct underlying factors related to limb movement and effector (usually the hand) configuration. In Experiment 2, subjects sorted a subset of the actions by similarity of movement. Clustering and multidimensional scaling solutions indicated that the six initial dimensions contributed to similarity judgments, along with additional parameters. The results support the existence of cognitively accessible, but still relatively specific, representations of functional actions, with potential implications for motor and memory performance.

Adult↗
PubMed1993

Haptic identification of objects and their depictions.

Haptic identification of real objects is superior to that of raised two-dimensional (2-D) depictions. Three explanations of real-object superiority were investigated: contribution of material information, contribution of 3-D shape and size, and greater potential for integration across the fingers. In Experiment 1, subjects, while wearing gloves that gently attenuated material information, haptically identified real objects that provided reduced cues to compliance, mass, and part motion. The gloves permitted exploration with free hand movement, a single outstretched finger, or five outstretched fingers. Performance decreased over these three conditions but was superior to identification of pictures of the same objects in all cases, indicating the contribution of 3-D structure and integration across the fingers. Picture performance was also better with five fingers than with one. In Experiment 2, the subjects wore open-fingered gloves, which provided them with material information. Consequently, the effect of type of exploration was substantially reduced but not eliminated. Material compensates somewhat for limited access to object structure but is not the primary basis for haptic object identification.

Adult↗
PubMed1992

Stages of manual exploration in haptic object identification.

In a yes/no identification task using touch alone, subjects indicated whether an object belonged to a named category. Previously, we found that subjects explored in two stages--first grasping and lifting the object, then executing further exploratory procedures (Lederman & Klatzky, 1990b). We proposed that Stage 1 (grasp/lift) was sufficient to extract coarse information about multiple object properties, whereas Stage 2 was directed toward precise information about particularly diagnostic properties. In the current study, subjects were initially constrained to grasping and lifting, after which they could explore further. Accuracy was above chance after Stage 1, confirming our assumption that the grasp/lift combination was broadly useful. Stage 2 increased accuracy and confidence. It primarily elicited exploratory procedures associated with object geometry, but exploration was also influenced by diagnostic object properties.

Adult↗
PubMed1991

Imagined haptic exploration in judgments of object properties.

In Experiment 1, each subject rated a single, named object for its roughness, hardness, temperature, weight, size, or shape. In Experiment 2, each subject compared one pair of objects along the same dimensions. In both studies, a substantial proportion of subjects who judged the first four dimensions imagined a hand making exploratory movements appropriate for the designated information. The proportion of hand-exploration images decreased substantially when judging size or shape, or when judgments could be made readily through general semantic knowledge. The results suggest that the incorporation of haptic exploration into visual imagery provides access to information about haptically accessible object properties.

Adult↗
PubMed1991

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.

Adult↗
PubMed1990

Haptic classification of common objects: knowledge-driven exploration.

In Experiment 1, haptically available object properties that would be diagnostic for constrained common object classification at the basic and subordinate levels were elicited in a questionnaire. The results are considered in terms of the nature of the haptically derived representations of common objects. Initial data are also presented regarding knowledge of the natural co-occurrence of properties in haptic object perception. In Experiment 2, the hand movements executed during haptic classification of manipulable common objects were examined. Manual exploration consisted of a two-stage sequence, an initial generalized "grasp-and -lift" routine, followed by a series of more specialized hand-movement patterns strongly driven by knowledge of the property diagnosticity for the specific object (obtained in Experiment 1). The current results may guide computational models of human haptic object classification and the development of perceptual systems for robots equipped with sensate dextrous hands, capable of intelligent exploration, recognition, and manipulation of concrete objects.

Adult↗
PubMed1990

Perceptual asymmetries in the somatosensory system: a dichhaptic experiment and critical review of the literature from 1929 to 1986.

Dichhaptic matching of 3-D nonsense shapes was used to assess sex-specific differences in haptics. In an initial object exploration/description phase, strategy was manipulated with instructions to encode each object using either a visual image (which was drawn) or verbal description (tape recorded). These drawings or tape recordings were subsequently used on their own to identify each object. Attempts were made to maintain similarity between the verbal and spatial procedures, to avoid methodological biasing of hand superiorities (e.g., the same number of alternatives and the same presentation times were used). Differences in hand superiority did not, however, result. To obtain a broader perspective, a critical review table was compiled of the entire somatosensory asymmetry literature. Clear patterns emerged for all types of task when results potentially stemming from methodological biases and those based on only certain levels of samples were excluded. Somatosensory perceptual asymmetries are not robust, although hand superiorities are in the predicted direction when they do occur; nevertheless, we find little support for sex-specific asymmetries in these studies. Dichhaptic presentations lack the efficacy of other somatosensory (as well as tachistoscopic) tasks overall, possibly because of the time scale necessary for free haptic exploration.

Adult↗
PubMed1990

Haptic integration of planar size with hardness, texture, and planar contour.

Three studies investigate the role of size information in haptic classification of custom-made planar objects when size covaries with hardness, texture, or planar contour. The haptic exploratory procedure (Lederman & Klatzky, 1987) associated with size extraction is also sufficient for encoding shape, which should promote their integration. Experiment 1 showed substantial facilitation of classification by redundant size and shape cues, indicating the coprocessing of size and shape. Experiments 2 and 3 used a withdrawal paradigm: Classification trials began with two redundant properties, and one was then held constant (withdrawn). Experiment 2 showed that when size and shape were redundant, withdrawal of either impaired responses, whereas when size was redundant with texture or hardness, only size withdrawal had an effect. Experiment 3 demonstrated that this size weighting was not restricted to a single procedure for exploration. Size appears to be highly weighted in haptic classification and potentially integrated with other properties having compatible methods of extraction.

Adult↗
PubMed1990

Visual mediation and the haptic recognition of two-dimensional pictures of common objects.

A set of three experiments was performed to investigate the role of visual imaging in the haptic recognition of raised-line depictions of common objects. Blindfolded, sighted (Experiment 1) observers performed the task very poorly, while several findings converged to indicate that a visual translation process was adopted. These included (1) strong correlation between image-ability ratings (obtained in Experiment 1 and, independently, in Experiment 2) and both recognition speed and accuracy, (2) superior performance with, and greater ease of imaging, two-dimensional as opposed to three-dimensional depictions, despite equivalence in rated line complexity, and (3) a significant correlation between the general ability of the observer to image and obtained imageability ratings of the stimulus depictions. That congenitally blind observers performed the same task even more poorly, while their performance did not differ for two- versus three-dimensional depictions (Experiment 3), provides further evidence that visual translation was used by the sighted. Such limited performance is contrasted with the considerable skill with which real common objects are processed and recognized haptically. The reasons for the general difference in the haptic performance of two- versus three-dimensional tasks are considered. Implications for the presentation of spatial information in the form of tangible graphics displays for the blind are also discussed.

Adult↗
PubMed1989

Length distortion of temporally extended visual displays: similarity to haptic spatial perception.

Three experiments were designed to investigate length distortion--the tendency to inflate estimates of the inferred distance between two points, as the length of a circuitous pathway between them increases. This phenomenon, previously demonstrated with haptic and locomotor exploration (Lederman, Klatzky, Collins, & Wardell, 1987), was extended to vision through the presentation of pathways as a temporal sequence of illuminated points. The magnitude of the visual effect was less than that previously found in haptics, and conditions promoting the effect included a relatively slow presentation rate and moderately complex pathways. Commonalities in the pattern, if not the magnitude, of length distortion in vision and haptics suggest that similar processes of spatial encoding may underlie the phenomenon in both domains.

Adult↗
PubMed1987

Exploring environments by hand or foot: time-based heuristics for encoding distance in movement space.

In Experiment 1, blindfolded observers judged (a) the distance of pathways felt by hand and (b) the straight-line distance between pathway endpoints inferred from such exploration. In Experiment 2, blindfolded observers made corresponding estimates after traversing similar pathways on foot. Pathways were explored under three different speeds. Under both manipulatory and ambulatory exploration, there was substantial length distortion of inferred distance: The straight-line distance was increasingly overestimated with increases in the length of the explored pathway. With manipulatory exploration, slower movements increased length distortion, but duration effects proved secondary to effects of spatial extent. For ambulatory exploration, no duration effects were obtained. Observers used time-independent heuristics, that is, a footstep metric for estimating the pathway actually travelled and a spatial imaging strategy for estimating the inferred line between pathway endpoints. The studies establish length distortion as a general phenomenon in movement space and identify its major causes as spatial rather than temporal.

Adult↗
PubMed1986

Perception of texture by vision and touch: multidimensionality and intersensory integration.

A series of six experiments offers converging evidence that there is no fixed dominance hierarchy for the perception of textured patterns, and in doing so, highlights the importance of recognizing the multidimensionality of texture perception. The relative bias between vision and touch was reversed or considerably altered using both discrepancy and nondiscrepancy paradigms. This shift was achieved merely by directing observers to judge different dimensions of the same textured surface. Experiments 1, 4, and 5 showed relatively strong emphasis on visual as opposed to tactual cues regarding the spatial density of raised dot patterns. In contrast, Experiments 2, 3, and 6 demonstrated considerably greater emphasis on the tactual as opposed to visual cues when observers were instructed to judge the roughness of the same surfaces. The results of the experiments were discussed in terms of a modality appropriateness interpretation of intersensory bias. A weighted averaging model appeared to describe the nature of the intersensory integration process for both spatial density and roughness perception.

Adolescent↗
PubMed1985

Spatial and movement-based heuristics for encoding pattern information through touch.

Seven experiments investigated the heuristics people use to encode spatial pattern information through touch. Observers traced a tangible pathway with one hand and then answered questions about either the euclidean line between the pathway endpoints or the pathway itself. Parameters of the euclidean line were held constant, while characteristics of the felt pathway were manipulated. Experiments 1-4 showed that blindfolded sighted and blind observers increasingly overestimated the length of the euclidean line as the length of the explored pathway increased. This indicates a movement-based heuristic for encoding distance. Experiments 5-7 indicated that judgments of the position of the euclidean line did not vary with the position of the felt pathway or the extent to which it deviated from that line. Instead, the results indicated that observers relied on implicit spatial axes, which are movement independent, to judge position. These and other results have implications for theories of haptic encoding of spatial pattern and for the construction of tangible graphics displays.

Adult↗