Tactual perception: a review of experimental variables and procedures <s> Type of stimuli: concrete stimuli <s> Subjects identified common objects under conditions of a “haptic glance,” a brief haptic exposure that placed severe spatial and temporal constraints on stimulus processing. They received no advance cue, a superordinate-level name as cue, or a superordinate and basic-level name as cue. The objects varied in size relative to the fingertip and in the most diagnostic attribute, either texture or shape. The data suggest that object recognition can occur when global volumetric primitives cannot directly be extracted. Even with no cue, confusion errors resembled the target object and indicated extraction of material and local shape information, which was sufficient to provide accuracy above 20%. Performance improved with cuing, and the effect of exposure duration was observed primarily with minimal cuing, indicating compensatory effects of top-down processing. <s> BIB001 </s> Tactual perception: a review of experimental variables and procedures <s> Type of stimuli: concrete stimuli <s> 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. <s> BIB002 </s> Tactual perception: a review of experimental variables and procedures <s> Type of stimuli: concrete stimuli <s> Five-year-old children explored multidimensional objects either haptically or visually and then were tested for recognition with target and distractor items in either the same or the alternative modality. In Experiments 1 and 2, haptic, visual, and cross-modal recognition were all nearly with familiar objects; haptic and visual recognition were also excellent with unfamiliar objects, but cross-modal recognition was less accurate. In Experiment 3, cross-modal recognition was also less accurate than within-mode recognition with familiar objects that were members of the same basic-level category. The results indicate that children's haptic recognition is remarkably good, that cross-modal recognition is otherwise constrained, and that cross-modal recognition may be accomplished differently for familiar and unfamiliar objects. <s> BIB003 </s> Tactual perception: a review of experimental variables and procedures <s> Type of stimuli: concrete stimuli <s> Abstract Although the perception of our world is experienced as effortless, the processes that underlie object recognition in the brain are often difficult to determine. In this chapter, we review the effects of familiarity on the recognition of moving or static objects. In particular, we concentrate on exemplar-level stimuli such as walking humans, unfamiliar objects and faces. We found that the perception of these objects can be affected by their familiarity; for example the learned view of an object or the learned dynamic pattern can influence object perception. Deviations in the viewpoint from the familiar viewpoint, or changes in the temporal pattern of the objects can result in some reduction of efficiency in the perception of the object. Furthermore, more efficient sex categorization and crossmodal matching were found for familiar than for unfamiliar faces. In sum, we find that our perceptual system is organized around familiar events and that perception is most efficient with these learned events. <s> BIB004 </s> Tactual perception: a review of experimental variables and procedures <s> Type of stimuli: concrete stimuli <s> Two experiments used visual-, verbal-, and haptic-interference tasks during encoding (Experiment 1) and retrieval (Experiment 2) to examine mental representation of familiar and unfamiliar objects in visual/haptic crossmodal memory. Three competing theories are discussed, which variously suggest that these representations are: (a) visual; (b) dual-code—visual for unfamiliar objects but visual and verbal for familiar objects; or (c) amodal. The results suggest that representations of unfamiliar objects are primarily visual but that crossmodal memory for familiar objects may rely on a network of different representations. The pattern of verbal-interference effects suggests that verbal strategies facilitate encoding of unfamiliar objects regardless of modality, but only haptic recognition regardless of familiarity. The results raise further research questions about all three theoretical approaches. <s> BIB005 </s> Tactual perception: a review of experimental variables and procedures <s> Type of stimuli: concrete stimuli <s> Previous investigations of visual object recognition have found that some views of both familiar and unfamiliar objects promote more efficient recognition performance than other views. These views are considered as canonical and are often the views that present the most information about an object's 3-D structure and features in the image. Although objects can also be efficiently recognised with touch alone, little is known whether some views promote more efficient recognition than others. This may seem unlikely, given that the object structure and features are readily available to the hand during object exploration. We conducted two experiments to investigate whether canonical views existed in haptic object recognition. In the first, participants were required to position each object in a way that would present the best view for learning the object with touch alone. We found a large degree of consistency of viewpoint position across participants for both familiar and unfamiliar objects. In a second exper... <s> BIB006 </s> Tactual perception: a review of experimental variables and procedures <s> Type of stimuli: concrete stimuli <s> In four experiments, we examined the haptic recognition of 3-D objects. In Experiment 1, blindfolded participants named everyday objects presented haptically in two blocks. There was significant priming of naming, but no cost of an object changing orientation between blocks. However, typical orientations of objects were recognized more quickly than nonstandard orientations. In Experiment 2, participants accurately performed an unannounced test of memory for orientation. The lack of orientation-specific priming in Experiment 1, therefore, was not because participants could not remember the orientation at which they had first felt an object. In Experiment 3, we examined haptic naming of objects that were primed either haptically or visually. Haptic priming was greater than visual priming, although significant cross-modal priming was also observed. In Experiment 4, we tested recognition memory for familiar and unfamiliar objects using an old-new recognition task. Objects were recognized best when they were presented in the same orientation in both blocks, suggesting that haptic object recognition is orientation sensitive. Photographs of the unfamiliar objects may be downloaded from www.psychonomic.org/archive. <s> BIB007 </s> Tactual perception: a review of experimental variables and procedures <s> Type of stimuli: concrete stimuli <s> Two experiments examined the effects of size changes on haptic object recognition. In Experiment 1, participants named one of three exemplars (a standard-size-and-shape, different-size, or different-shape exemplar) of 36 categories of real, familiar objects. They then performed an old/new recognition task on the basis of object identity for the standard exemplars of all 36 objects. Half of the participants performed both blocks visually; the other half performed both blocks haptically. The participants were able to efficiently name unusually sized objects haptically, consistent with previous findings of good recognition of small-scale models of stimuli (Lawson, in press). However, performance was impaired for both visual and haptic old/new recognition when objects changed size or shape between blocks. In Experiment 2, participants performed a short-term haptic shape-matching task using 3-D plastic models of familiar objects, and as in Experiment 1, a cost emerged for ignoring the irrelevant size change. Like its visual counterpart, haptic object recognition incurs a significant but modest cost for generalizing across size changes. <s> BIB008 </s> Tactual perception: a review of experimental variables and procedures <s> Type of stimuli: concrete stimuli <s> Abstract In the preceding paper (Lacey, S., Flueckiger, P., Stilla, R., Lava, M., Sathian, K., 2009a. Object familiarity modulates involvement of visual imagery in haptic shape perception), we showed that the activations evoked by visual imagery overlapped more extensively, and their magnitudes were more correlated, with those evoked during haptic shape perception of familiar, compared to unfamiliar, objects. Here we used task-specific analyses of functional and effective connectivity to provide convergent evidence. These analyses showed that the visual imagery and familiar haptic shape tasks activated similar networks, whereas the unfamiliar haptic shape task activated a different network. Multivariate Granger causality analyses of effective connectivity, in both a conventional form and one purged of zero-lag correlations, showed that the visual imagery and familiar haptic shape networks involved top-down paths from prefrontal cortex into the lateral occipital complex (LOC), whereas the unfamiliar haptic shape network was characterized by bottom-up, somatosensory inputs into the LOC. We conclude that shape representations in the LOC are flexibly accessible, either top-down or bottom-up, according to task demands, and that visual imagery is more involved in LOC activation during haptic shape perception when objects are familiar, compared to unfamiliar. <s> BIB009
This section regards performance with concrete stimuliusually three-dimensional and common stimuli-evaluating differences between familiar and unfamiliar stimuli and more recent topic: the tactual perception of faces. Familiar and unfamiliar stimuli BIB004 presented a thorough review on the role of familiarity in the perception of objects, faces and movement. The authors concluded that stimulus familiarity is a central feature in perception and that people are more efficient responding to learned than unknown objects, which led the authors to assume that our perceptual system is organised through these familiar stimuli or events. A study with 5-year-old children showed that they were very good at haptically recognising a list of 16 unfamiliar objects (e.g., segments of other objects), and their performance was optimal in the familiar objects' set, with children being able to correctly recognise about 15 out of 16 presented objects BIB003 . Also BIB005 , in a study with adults in a crossmodal visuo-haptic paradigm, reported that participants were able to recognise between 15 and 16 objects in a 16-object set for familiar items and around 13-14 objects in unfamiliar object trials. In two recent functional magnetic resonance studies BIB009 , the authors argued that crossmodal visuo-tactile interactions in the brain are modulated by the item's familiarity, when they found that the activation overlapping between haptic and visual trials was bigger for familiar than unfamiliar objects. A series of studies has also shown that people have preferred ''views'' or perspectives to perceive objects by touch. These views are called canonical views and had been studied in vision, with people being more effective at recognising objects presented from a familiar perspective than when presented in a different orientation BIB002 . Under free exploration conditions, participants still preferred the haptic canonical view to manipulate objects and the hands favoured a ''back'' perspective instead of the ''front'' perspective, typical of vision BIB002 . Participants showed coherence in the selection of haptic canonical views, either for familiar or for unfamiliar stimuli, and these perspectives allowed a better recognition performance BIB006 ). The viewpoint dependency in touch is verified either for stimuli learned in the experimental task or for everyday stimuli and is mediated by task difficulty, with the most difficult discrimination tasks being more impaired by changes in stimuli perspective  . Even within the viewpoint or orientation procedures, differences can be found between familiar and unfamiliar objects BIB007 , with objects' recognition being dependent on the orientation in which stimuli were presented, for both types of objects, but with larger errors for unfamiliar than for familiar objects. Haptic recognition of familiar objects is also sensitive to size and shape changes BIB008 . In this study, participants were asked to recognise objects based on identity and ignoring size or shape variations. Results showed that generalisation occurred in touch, but there was a cost, since participant's recognition performance was lightly impaired in trials in which a change was present.  had shown touch to be an effective and highly accurate system in the perception of familiar everyday objects and had defined that people need about two to 3 s (sometimes less) to be able to identify a stimulus presented through touch only. A later work BIB001 revealed that participants were able to identify familiar objects without any cues with presentations as short as 200 ms, with an accuracy level of 20 %. When analysing the errors, the authors found that the most typical errors corresponded to identifications of other items similar to the target (e.g., identifying a pencil as a pen). Familiarity is a central variable in tactual cognition, and the ability of the haptic system in recognition and perception of these stimuli must be explored, since it can provide valuable information to the understanding of touch.