Effects of visual information regarding allocentric processing in haptic parallelity matching

Research has revealed that haptic perception of parallelity deviates from physical reality. Large and systematic deviations have been found in haptic parallelity matching most likely due to the influence of the hand-centered egocentric reference frame. Providing information that increases the influence of allocentric processing has been shown to improve performance on haptic matching. In this study allocentric processing was stimulated by providing informative vision in haptic matching tasks that were performed using hand- and arm-centered reference frames.     

Perceptual orientational asymmetries: A comparison of visual and haptic space

Stimulus orientation discrimination was investigated in visual and haptic modalities under conditions of simultaneous matching and memory. Discrimination of vertical and horizontal was significantly more accurate than discrimination of oblique stimulus orientations (45°, 135°, 225°, and 315°) for both modalities; haptic errors, however, were significantly greater at each orientation. While subjects were reliably more accurate in visually matching oblique stimulus orientations to a standard than producing them from memory, for the haptic modality, differences between memory and matching conditions were less consistent across the orientations sampled.     

Touching on face space: Comparing visual and haptic processing of face shapes

The idea that faces are represented within a structured face space (Valentine Quarterly Journal of Experimental Psychology 43: 161–204, 1991) has gained considerable experimental support, from both physiological and perceptual studies. Recent work has also shown that faces can even be recognized haptically—that is, from touch alone. Although some evidence favors congruent processing strategies in the visual and haptic processing of faces, the question of how similar the two modalities are in terms of face processing remains open. Here, this question was addressed by asking whether there is evidence for a haptic face space, and if so, how it compares to visual face space. For this, a physical face space was created, consisting of six laser-scanned individual faces, their morphed average, 50 %-morphs between two individual faces, as well as 50 %-morphs of the individual faces with the average, resulting in a set of 19 faces. Participants then rated either the visual or haptic pairwise similarity of the tangible 3-D face shapes. Multidimensional scaling analyses showed that both modalities extracted perceptual spaces that conformed to critical predictions of the face space framework, hence providing support for similar processing of complex face shapes in haptics and vision. Despite the overall similarities, however, systematic differences also emerged between the visual and haptic data. These differences are discussed in the context of face processing and complex-shape processing in vision and haptics.     

Psychological analyses of haptic and haptic-visual judgements of extent

Magnitude estimates of haptic extent resulted in positively accelerated psychophysical power function with an exponent of 1.18. However, in two further experiments right-handed male subjects made rating-scale judgements of the combined width of two stimulus blocks. Six widths were used and five replications of the 36 factorial combinations were presented to each subject. In Experiment II both stimuli were out of view and one was held between the thumb and index finger of each hand. In Experiment III one stimulus was held out of view between thumb and finger of the right hand and the second was shown to the subject. Mean ratings in both experiments were fit by a model which assumes that responses are a weighted average of the scale values of the two stimuli (Anderson, 1974a).     

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 Bourdon illusion in haptic space

A strong Bourdon illusion-the apparent bentness of a straight edge-in the active haptic mode was established in two experiments. Blindfolded subjects clasped the opposite surfaces of an object with the same frontal profile as the visual figure between thumb and forefinger and moved the latter together from end to end across the object. When the two triangular components of the objects were rotated through 180 degrees so that their bases instead of their apexes were contiguous, the illusion was reversed in direction and reduced by about half, as with the visual illusion. It was concluded that the active haptic Bourdon illusion is basically the same as the visual illusion and can be accounted for by a compromise in perception between the orientation of the test surface and that of the object of which it is an integral part.     

The visual and haptic perception of natural object shape

In this study, we evaluated observers' ability to compare naturally shaped three-dimensional (3-D) objects, using their senses of vision and touch. In one experiment, the observers haptically manipulated 1 object and then indicated which of 12 visible objects possessed the same shape. In the second experiment, pairs of objects were presented, and the observers indicated whether their 3-D shape was the same or different. The 2 objects were presented either unimodally (vision-vision or haptic-haptic) or cross-modally (vision-haptic or haptic-vision). In both experiments, the observers were able to compare 3-D shape across modalities with reasonably high levels of accuracy. In Experiment 1, for example, the observers' matching performance rose to 72% correct (chance performance was 8.3%) after five experimental sessions. In Experiment 2, small (but significant) differences in performance were obtained between the unimodal vision-vision condition and the two cross-modal conditions. Taken together, the results suggest that vision and touch have functionally overlapping, but not necessarily equivalent, representations of 3-D shape.     

The influence of visual texture density gradients on relative distance judgements

A hypothesis derived from J. J. Gibson's psychophysical theory of space perception was tested. Subjects made monocular relative distance judgements by moving a marker to the apparent physical mid-point between two other fixed markers which were placed on a surface along the subjects' line of sight. Judgements were significantly influenced by the texture density gradients of stimulation derived from the surface over which they were made.     

The structure of haptic space in the blind and sighted

Summary The purpose of the present experiment was to analyse the metric of haptic space. The subjects were shown a goal-point, after having felt the sides of a right triangle with differing lengths. The subjects were then required to estimate the position of the goal-point in one of two ways, either along the hypotenuse from the starting point (a cognitive spatial orientation task) or via the sides touched previously (a perceptual spatial orientation task). They were asked to do this either by making a hand movement which would approximate the distance (motor estimate) or verbally (verbal estimate). There were four groups of subjects: congenitally blind (CB), adventitiously blind (AB), sighted under blindfold (SB), and sighted people with visual pre-orientation (SV). 10 subjects were in each group. The major results of the experiment were: (1) With all groups but SV a distortion was observed in the estimates of the shortest distance from the Euclidian metric to the city-block-metric. (2) The groups AB and SB produced the largest distortion from the Euclidian metric. (3) In the case of motor estimates, both cognitive and perceptual spatial orientation tasks led to congruent metrics. (4) With the exception of group SV verbal and motor estimates led to divergent metrics. The results are considered from the points of view of (a) empiricist theories, (b) theories of equal laws of structure for all sensory modalities, and (c) the hypothesis of transposition.This investigation was supported in part by the German Research Association (Deutsche Forschungsgemeinschaft); head of the research project Prof. Dr. F. Merz.I thank the staff of the Blind Mobility Research Unit of the University of Nottingham for the support in correcting the English translation.     

Keep an eye on your hands: on the role of visual mechanisms in processing of haptic space

The present paper reviews research on a haptic orientation processing. Central is a task in which a test bar has to be set parallel to a reference bar at another location. Introducing a delay between inspecting the reference bar and setting the test bar leads to a surprising improvement. Moreover, offering visual background information also elevates performance. Interestingly, (congenitally) blind individuals do not or to a weaker extent show the improvement with time, while in parallel to this, they appear to benefit less from spatial imagery processing. Together this strongly points to an important role for visual processing mechanisms in the perception of haptic inputs.     

Embodied information affects judgements about politicians: The impact of haptic weight sensations and hand cleansing

Politicians' characteristics attract voters' attention and dominate impression formation. Thereby, social judgements are deduced from different information being available in a certain situation. The literature suggests that incidental bodily sensations can influence judgement processes. Here, two bodily treatments—the haptic sensation of weight and the act of hand cleansing—simultaneously contribute to judgements about politicians. This study expands previous works by (a) investigating potential interactions of two haptic information cues, (b) providing evidence for the significant role of conceptual closeness between embodied cues and judgement dimensions, (c) showing that hand cleansing leads to harsher moral judgements independently of whether a misconduct has been committed or not, and (d) showing that the familiarity of the target to be judged does not moderate the effect of embodied information. The results demonstrate that judgements can be modulated by basal sensorimotor experiences. We discuss implications and the important issue of result generalisation and replicability.     

The effects of stimulus size on bisection judgements in near and far space

Primate data suggest that near (peripersonal) and far (extrapersonal) space are coded within distinct representations. Support for this claim has been gained from human studies of line bisection, many of which have focused on neuropsychological, rather than normative, samples. One important aspect of these bisection studies has been to control for the changes in angular extent of stimuli that normally accompany changes in viewing distance. The control of angular information, however, requires alterations in the linear dimensions (actual stimulus size) of stimuli. We report two experiments in which normal subjects made manual bisection judgements on stimuli positioned in near or far space, and which were oriented in either the left-right (Experiment 1) or radial plane (Experiment 2). Both experiments were designed to enable the separable effects of linear and angular extent to be disentangled. Viewing distance effects were obtained when angular information was controlled, but many of these were dependent on changes in linear extent, and were only apparent at the individual subject level. Our data confirm that genuine near/far effects may be observed in normative bisection, but that many previous studies which appeared to support a near/far distinction in both normal and brain-damaged bisection behaviour may reflect a failure to control for changes in stimulus size.     

The structure of frontoparallel haptic space is task dependent

In three experiments, we investigated the structure of frontoparallel haptic space. In the first experiment, we asked blindfolded participants to rotate a matching bar so that it felt parallel to the reference bar, the bars could be at various positions in the frontoparallel plane. Large systematic errors were observed, in which orientations that were perceived to be parallel were not physically parallel. In two subsequent experiments, we investigated the origin of these errors. In Experiment 2, we asked participants to verbally report the orientation of haptically presented bars. In this task, participants made errors that were considerably smaller than those made in Experiment 1. In Experiment 3, we asked participants to set bars in a verbally instructed orientation, and they also made errors significantly smaller than those observed in Experiment 1. The data suggest that the errors in the matching task originate from the transfer of the reference orientation to the matching-bar position.     

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.     

Viewpoint dependence in visual and haptic object recognition

On the whole, people recognize objects best when they see the objects from a familiar view and worse when they see the objects from views that were previously occluded from sight. Unexpectedly, we found haptic object recognition to be viewpoint-specific as well, even though hand movements were unrestricted. This viewpoint dependence was due to the hands preferring the back "view" of the objects. Furthermore, when the sensory modalities (visual vs. haptic) differed between learning an object and recognizing it, recognition performance was best when the objects were rotated back-to-front between learning and recognition. Our data indicate that the visual system recognizes the front view of objects best, whereas the hand recognizes objects best from the back.     

Supramodality effects in visual and haptic spatial processes

In this article, the authors investigated unimodal and cross-modal processes in spatial working memory. A number of locations had to be memorized within visual or haptic matrices according to different experimental conditions known to be critical in accounting for the effects of perception on imagery. Results reveal that some characteristics of the generated mental image remained strictly inherent to the modality in which information was acquired; in general, accuracy was higher when configurations were visually rather than haptically explored (Experiments 1 and 3). Interestingly, the same pattern emerged when the effects of simultaneous versus sequential processing of the stimuli inherent to vision and haptics were isolated from perceptual modality (Experiment 2). Supramodal elements were also identified (Experiment 3) that were specifically associated to the nature of the cognitive processes, regardless of the original characteristics of the sensory information. These data indicate that both unimodal modality-specific and higher order supramodal mechanisms are simultaneously used in spatial processes.