The effects of familiarity and orientation in the haptic change task.

In seven experiments we examined haptic memory for location, item information, and orientation for 12 tangible pictures, geometrical forms, and letter shapes in the change task. The study evaluated the influence of stimulus familiarity on change task performance. In the change task, participants are exposed to an array of patterns and subsequently have to indicate which ones have been altered on a second array. We also sought to determine whether prior demonstrations of female advantages in the haptic change task were reliable (Heller et al., 2010). The present experiments failed to replicate gender differences, overall with large samples. When participants were told about the nature of the picture change they should anticipate (45° or 90° rotation, location exchange), comparable performance was found for the groups in Experiment 1. In another experiment, participants were not told what sort of change might occur, and higher performance was found for the 90° rotation group than for the location exchange and 45° groups. Participants benefited from explicit instructions about the nature of the change. Telling participants the names of the raised-line pictures during initial study improved both change performance with the pictures and subsequent recognition. Changes derived from the substitution of new tangible print capital letters were easier to detect than location exchanges of the letters. Changes from letters to geometrical shapes were easy to detect. High performance resulted when participants were told to indicate which tangible letters were turned (45° or 90°) or exchanged in a final experiment. The results suggest the importance of pattern familiarity in haptic spatial memory.

The effect of visual magnification and reduction on perceived hand size.

The aim of the present study was to clarify the mechanisms underlying body understanding by examining the impact of visual experience (magnification and reduction) on perception of hand size and neutral external objects (squares). Independent groups of participants were asked to look through a 2× magnification lens, a ½-× reduction lens, or a control UV filter and to make visual size judgments about square stimuli and their hands. In Experiment 1, participants used a measuring device with unmarked wooden slats orientated in horizontal and radial/vertical space for their visual judgments. In Experiment 2, participants used an upright frontal slat for visual length judgments of their hands to eliminate any potential foreshortening in viewing the measurement apparatus. The results from the two experiments demonstrate that participants significantly underestimated both the square stimuli and their hands when they viewed them under a reduction lens. While overestimation and underestimation of squares was found for females in Experiment 2, males generally underestimated the squares. However, overestimation was not seen when the participants viewed their hands under a magnification lens. Implications of these findings are discussed.

The horizontal-vertical curvature illusion in touch is present in three-dimensional objects and raised lines.

The present study compared the strength of the horizontal-vertical illusion in blindfolded sighted people with raised-line curves and three-dimensional (3-D) objects. Although the horizontal-vertical curvature illusion has been reported with raised-line stimuli in both vision and touch, it was not known whether similar haptic distortion would be found with 3-D objects. Similar overestimation of verticals was found with both types of stimuli in Experiment 1. Experiment 2 used bimanual unrestricted exploration at the body midline and stimuli horizontal on the table surface or in the frontal plane. In Experiment 2, illusion strength was substantially stronger when the stimuli were frontal and diminished overall for the horizontal group. The horizontal-vertical illusion was strong with optimal methods of presentation (free bimanual exploration) in Experiment 2, even where radial-tangential scanning could not be a causal factor in the frontal group. The results suggest that illusory distortion in haptics is not the result of the use of raised lines, and these patterns can be effective surrogates for 3-D objects.

Attenuating the haptic horizontal-vertical curvature illusion.

In a number of experiments, blindfolded subjects traced convex curves whose verticals were equal to their horizontal extent at the base. Overestimation of verticals, as compared with horizontals, was found, indicating the presence of a horizontal-vertical illusion with haptic curves, as well as with visible curves. Experiment 1 showed that the illusion occurred with stimuli in the frontal plane and with stimuli that were flat on the table surface in vision and touch. In the second experiment, the stimuli were rotated, and differences between vision and touch were revealed, with a stronger illusion in touch. The haptic horizontal-vertical illusion was virtually eliminated when the stimuli were bimanually touched using free exploration at the body midline, but a strong illusion was obtained when curves were felt with two index fingers or with a single hand at the midline. Bimanual exploration eliminated the illusion for smaller 2.5- through 10.2-cm stimuli, but a weakened illusion remained for the largest 12.7-cm patterns. The illusion was present when the stimuli were bimanually explored in the left and right hemispace. Thus, the benefits of bimanual exploration derived from the use of the two hands at the body midline combined with free exploration, rather than from bimanual free exploration per se. The results indicate the importance of haptic exploration at the body midline, where the body can serve as a familiar reference metric for size judgments. Alternative interpretations of the results are discussed, including the impact of movement-based heuristics as a causal factor for the illusion. It was suggested that tracing the curve's peak served to bisect the curve in haptics, because of the change in direction.

Sex differences in the haptic change task.

Three experiments examined gender differences in picture location memory in the sense of touch involving the change task. In Experiments 1 and 2, blindfolded sighted participants felt 15 tangible raised-line pictures and memorized their locations for 8 min. Subsequently, they felt another set of raised-line pictures that were identical to the original set, but locations were exchanged for 6 of them. The change task required participants to indicate which raised-line pictures were moved to new locations and which were not moved. It was expected that females would show superior picture location memory compared with males. The results showed that females had a significantly higher number of correct picture location judgments than males in Experiment 1. No differences appeared between males and females on the change task when the task was much more difficult and the raised-line pictures were irregularly arrayed in the second experiment. Task difficulty was too high in Experiment 2, and a third experiment reduced the number of pictures in the irregular array to 12. Females performed better than males in Experiment 3. Gender differences in the change task are small in magnitude in touch as well as in vision. The results of the present experiments using touch are consistent with the larger literature in vision.

The influence of viewpoint and object detail in blind people when matching pictures to complex objects.

We examined haptic viewpoint effects in blindfolded-sighted (BS) and visually impaired subjects: early blind (EB), late blind (LB), and very low vision (VLV). Participants felt complex objects and matched tangible pictures to them. In experiment 1, the EB and BS subjects had similar overall performance. Experiment 2 showed that the presence of a detail on the target object lowered performance in the BS subjects, and that matching accuracy was lower overall for top views for the blind subjects. In experiments 3-5, EB, LB, VLV, and BS subjects made judgments about perspective pictures of a model house with more salient object details. In experiment 3, performance was higher for side views than for corner views. Elevated side views were identified more readily than elevated corner views in experiment 4. Performance for top views was higher than for elevated side views in experiment 5, given the relative simplicity of the top-view depictions and salient details. The EB and BS participants had somewhat lower matching accuracy scores than the other groups. We suggest that visual experience is helpful, but not essential for picture perception. Viewpoint effects may vary with experience and object complexity, but the relevant experience need not be specifically visual in nature.

The effects of curvature on haptic judgments of extent in sighted and blind people.

A series of experiments was carried out to examine the effect of curvature on haptic judgments of extent in sighted and blind individuals. Experiment 1 showed that diameters connecting the endpoints of semicircular lines were underestimated with respect to straight lines, but failed to show an effect of visual experience on length judgments. In experiment 2 we tested are lengths. The effects of curvature on perceived path length were weaker, but were still present in this experiment. Visual experience had no effect on path length judgments. Another experiment was performed to examine the effect of repeated tracing (1, 5, 9, or unlimited number of traces) on judgments of the lengths of straight lines and diameters of semicircles. Judgments of extent were more accurate when subjects engaged in larger numbers of traces. There was no effect of number of traces on curve-height judgments, suggesting that subjects were not using height estimates to judge diameters of semicircles. In a further experiment we tested the effect of number of traces on curves that varied in height. Restricting subjects to a single trace magnified the effect of path length on judgments of the distance between the endpoints of curves. Additional experiments showed that curvature effects on diameter judgments were not eliminated when stimuli were in the frontal plane or when the curves were explored with the use of two hands. Arm support had no effect on judged length in experiment 7. A final experiment showed a robust horizontal vertical illusion in haptic perception of convex curves, with overestimation of the heights of the curves compared with their widths. The practical and theoretical implications of the results are discussed.

Selective attention modulates visual and haptic repetition priming: effects in aging and Alzheimer's disease.

In two experiments, we examined the effect of selective attention at encoding on repetition priming in normal aging and Alzheimer's disease (AD) patients for objects presented visually (experiment 1) or haptically (experiment 2). We used a repetition priming paradigm combined with a selective attention procedure at encoding. Reliable priming was found for both young adults and healthy older participants for visually presented pictures (experiment 1) as well as for haptically presented objects (experiment 2). However, this was only found for attended and not for unattended stimuli. The results suggest that independently of the perceptual modality, repetition priming requires attention at encoding and that perceptual facilitation is maintained in normal aging. However, AD patients did not show priming for attended stimuli, or for unattended visual or haptic objects. These findings suggest an early deficit of selective attention in AD. Results are discussed from a cognitive neuroscience approach.

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.

Pattern perception and pictures for the blind

This article reviews recent research on perception of tangible pictures insighted and blind people. Haptic picture naming accuracy is dependent uponfamiliarity and access to semantic memory, just as in visual recognition.Performance is high when haptic picture recognition tasks do not dependupon semantic memory. Viewpoint matters for the ease or difficulty ofinterpreting haptic pictures of solid objects. Top views were easiest forsighted and blind persons when geometrical solids had constant crosssectionsin the vertical axis. The presence or absence of viewpoint effectsdepends upon the nature of the solids that are represented. Congenitallyblind people do not spontaneously produce perspective drawings, but recentdata suggests that depictions including linear perspective can be understoodafter minimal experience. The results suggest that two-dimensionalconfigurations are not necessarily problematic for touch

The influence of exploration mode, orientation, and configuration on the haptic Müller-Lyer illusion.

We studied the impact of manner of exploration, orientation, spatial position, and configuration on the haptic Müller-Lyer illusion. Blindfolded sighted subjects felt raised-line Müller-Lyer and control stimuli. The stimuli were felt by tracing with the index finger, free exploration, grasping with the index finger and thumb, or by measuring with the use of any two or more fingers. For haptic judgments of extent a sliding tangible ruler was used. The illusion was present in all exploration conditions, with overestimation of the wings-out compared to wings-in stimuli. Tracing with the index finger reduced the magnitude of the illusion. However, tracing and grasping induced an overall underestimation of size. The illusion was greatly attenuated when stimuli were felt with the index fingers of both hands. Illusory misperception was not altered by the position in space of the Müller-Lyer stimuli. No effects of changes in the thickness of the line shaft were found, but there were effects of the length of the wing endings for the smaller, 5.1 cm stimuli. The theoretical and practical implications of the results are discussed.

Objects, raised lines, and the haptic horizontal-vertical illusion.

Experiments were conducted to determine whether the haptic horizontal-vertical illusion occurs with solid, three-dimensional objects as well as with tangible lines. The objects consisted of round or square bases, with dowel rods projecting above them at heights equal to the widths of the horizontal bases. A negative illusion, with overestimation of horizontals, was found with free haptic exploration, but not with tracing with the fingertip. The negative illusion occurred when subjects felt wooden Ls and inverted Ts with a grasping, pincers motion of the index finger and thumb. The presence or absence of illusory misperception was dependent upon exploration strategy, since the negative illusion vanished with finger tracing. A negative illusion was also found when subjects adjusted a vertical dowel so that it was judged to be equal in extent to a round or square base. A general overestimation of judged size derived from the pincers response measure, but was not found with the use of a tangible ruler. Comparable illusory results are most likely when drawings and objects promote similar haptic scanning methods. The results were consistent with the idea that the orientation of an edge or line is more important than whether one explores a tangible line or a three-dimensional object.

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.

The haptic Müller-Lyer illusion in sighted and blind people.

We examined the effect of visual experience on the haptic Müller-Lyer illusion. Subjects made size estimates of raised lines by using a sliding haptic ruler. Independent groups of blind-folded-sighted, late-blind, congenitally blind, and low-vision subjects judged the sizes of wings-in and wings-out stimuli, plain lines, and lines with short vertical ends. An illusion was found, since the wings-in stimuli were judged as shorter than the wings-out patterns and all of the other stimuli. Subjects generally underestimated the lengths of lines. In a second experiment we found a nonsignificant difference between length judgments of raised lines as opposed to smooth wooden dowels. The strength of the haptic illusion depends upon the angles of the wings, with a much stronger illusion for more acute angles. The effect of visual status was nonsignificant, suggesting that spatial distortion in the haptic Müller-Lyer illusion does not depend upon visual imagery or visual experience.

Tactile picture perception in sighted and blind people.

This paper reviews recent research on the perception of tangible pictures by sighted people and those who are blind or have extremely low vision. Raised-line pictures are useful for evaluating spatial cognition in congenitally blind people. The ease or difficulty of picture recognition is shown to vary with complexity, familiarity, and categorical information. Blind people are able to use pictorial displays effectively, but may benefit from instruction when complex depictions of three-dimensional objects involve foreshortening.

Tangible pictures: viewpoint effects and linear perspective in visually impaired people.

Perception of raised-line pictures in blindfolded-sighted, congenitally blind, late-blind, and low-vision subjects was studied in a series of experiments. The major aim of the study was to examine the value of perspective drawings for haptic pictures and visually impaired individuals. In experiment 1, subjects felt two wooden boards joined at 45 degrees, 90 degrees, or 135 degrees, and were instructed to pick the correct perspective drawing from among four choices. The first experiment on perspective found a significant effect of visual status, with much higher performance by the low-vision subjects. Mean performance for the congenitally blind subjects was not significantly different from that of the late-blind and blindfolded-sighted subjects. In a further experiment, blindfolded subjects drew tangible pictures of three-dimensional (3-D) geometric solids, and then engaged in a matching task. Counter to expectations, performance was not impaired for the 3-D drawings as compared with the frontal viewpoints. Subjects were also especially fast and more accurate when matching top views. Experiment 5 showed that top views were easiest for all of the visually impaired subjects, including those who were congenitally blind. Experiment 5 yielded higher performance for 3-D than frontal viewpoints. The results of all of the experiments were consistent with the idea that visual experience is not necessary for understanding perspective drawings of geometrical objects.

Recodificacao da captura haptica de objetos tangiveis para uma transcricao pictorica

Pesquisas com o tato ativo mostram que o sistema sensorio tatil e surpreendentemente habil no reconhecimento de objetos tridimensionais. Certas configuracoes sao melhor reconhecidas quando aspectos diversos (caracterisitcas termicas, de textura, forma e tamanho) podem ser percebidos hapticamente em objetos tridimensionais. Espera-se que certas configuracoes sejam mais nomeadas e que certos padroes ocorram mais frequentemente com outros. Cegos congenitos e cegos adventicios tem se mostrado capazes de produzir desenhos em relevos, sendo sugerido que podem beneficiar-se do treino com figuras bidimensionais. Cegos congenitos, cegos adventicios e videntes vendados produziram 186 desenhos, apos terem examinado hapticamente ojetos 3D. Mil cento e dezesseis estimacoes de magnitude foram feitas para estabelecer o quanto esses desenhos representavam os objetos originais. O sistema haptico mostrou-se altamente capaz de reconhecer padroes 3D, havendo diferenca estatistica significativa entre os grupos. O status visual e a experiencia com o desenho parecem ter favorecido a producao de desenhos bidimensionais em relevo. Os cegos congenitos fizeram desenhos similares aos dos videntes e cegos adventicios (variando em funcao de suas habilidades pessoais e da complexidade dos objetos examinados), mesmo sem terem experiencia com as regras ou convencoes que regem a producao de figuras bidimensionais. A recodificacao da captura haptica para uma transcricao pictorica mostrou uma perda de qualidade das caracteristicas inerentes ao objeto original.