Although some studies have shown that haptic and visual identification seem to rely on similar processes, few studies have directly compared the two. We investigated haptic and visual object identification by asking participants to learn to recognize (Experiments 1, and 3), or to match (Experiment 2) novel objects that varied only in shape. Participants explored objects haptically, visually, or bimodally, and were then asked to identify objects haptically and/or visually. We demonstrated that patterns of identification errors were similar across identification modality, independently of learning and testing condition, suggesting that the haptic and visual representations in memory were similar. We also demonstrated that identification performance depended on both learning and testing conditions: visual identification surpassed haptic identification only when participants explored the objects visually or bimodally. When participants explored the objects haptically, haptic and visual identification were equivalent. Interestingly, when participants were simultaneously presented with two objects (one was presented haptically, and one was presented visually), object similarity only influenced performance when participants were asked to indicate whether the two objects were the same, or when participants had learned about the objects visually-without any haptic input. The results suggest that haptic and visual object representations rely on similar processes, that they may be shared, and that visual processing may not always lead to the best performance.

1712Which aspects of objects are important in visual identification? An object that is long, cylindrical, and tapered at one end is likely to be recognized as a "pen." Is it only the visual attributes of the pen that are involved in recognizing this object, or do certain nonvisual attributes stored within semantics (i.e., that a pen is held a certain way, and is used for writing) also play a role? We propose that in addition to the visual features of objects, other nonvisual features of these objects, specifically the actions habitually associated with these objects, play a key role in the visual identification and the naming of visually presented objects. We will briefly review the impact of visual and semantic similarity on visual identification before discussing the importance of action information and presenting the current studies. Visual Similarity Influences Visual IdentificationIn healthy participants, visual identification is influenced by visual similarity: Items that come from visually dissimilar categories are identified faster than items that come from visually similar categories (Dickerson & Humphreys, 1999;Humphreys, Riddoch, & Quinlan, 1988;Lloyd-Jones & Humphreys, 1997a, 1997b. Visual similarity also impacts the identification performance of patients with visual agnosia. In these patients, only the identification of certain categories of objects is impaired, a condition labeled category-specific visual agnosia (CSVA). In typical patients with CSVA, the visual identification of items like animals, fruits, vegetables, and musical instruments is impaired while the visual identification of items from other categories, such as tools, vehicles, and body parts is spared (Damasio, 1990;Dixon, Bub, & Arguin, 1997;Forde, Francis, Riddoch, Rumiati, & Humphreys, 1997;Gainotti & Silveri, 1996;Tranel, Logan, Frank, & Damasio, 1997). Arguably, the items that are typically impaired in CSVA patients come from categories where the exemplars are more visually similar to one another than the items that are spared. Gaffan and Heywood (1993) have highlighted the importance of visual similarity by showing that even nonhuman primates have more difficulty identifying drawings of animals than drawings of man-made objects, presumably because the shapes of animals are more visually similar than the shapes of manmade objects.In contrast to animals, objects such as tools share few visual attributes, and patients with CSVA show relatively few problems identifying them. However, for humans who know about animals and about tools, visual similarity may not be the only factor influencing visual object identification; semantic similarity may also play a role. Consider a patient who confuses depictions of lions and tigers but not depictions of hammers and saws. The felines are more visually similar than the tools, but also share more semantic features. Using depictions of real objects (e.g., comparing identification times of different felines to those of different articles of tools) it is difficult to disentangle the effects of vis...

Computer-generated shapes varying on visual dimensions such as curvature, tapering, and thickness have been used to investigate identification deficits in the category-specific visual agnosia (CSVA) Patient E.L.M.. However, whether the implemented variations on each of these dimensions were perceived by novice observers as "similar amounts of change" is unknown. To estimate distance in psychophysical shape space, sets of shapes were developed using two different scaling methods-an objective method based on visual search, and a subjective method based on judgments of similarity-and a third approach that did not involve scaling. How well each method estimated psychophysical shape space was assessed by measuring the confusions within memory among the shapes. The results suggested that, although neither of the approaches perfectly reflected psychophysical shape space, subjective scaling was a better estimator of distance in psychophysical shape space than were other approaches. The number of confusions produced on each set of shapes was used to develop a new set of shapes that accurately estimated distance in psychophysical shape space. These results suggest that a combination of approaches is preferable in order to accurately estimate distance in psychophysical shape space.

The role of premorbid expertise in object identification was investigated in the category-specific visual agnosia patient ELM. For several years prior to his stroke ELM played bugle in a military band. We surmised that band membership would lead to preferential exposure to, and expertise for, brass instruments relative to other musical-instrument families. To test this hypothesis we assessed ELM's musical instrument identification capability for brass and stringed instruments. Testing was conducted 14 years post-stroke. ELM listed significantly more correct attributes for five brass instruments than for five stringed instruments. On a picture-word matching task ELM showed significantly better identification of brass, relative to stringed, musical instruments. Finally, when ELM was required to pair novel shapes with labels denoting brass or stringed instruments, he made significantly more errors in the stringed-instrument condition than in the brass-instrument condition. We conclude that the elevated attribute knowledge accompanying expertise serves to increase the visual and semantic distance between objects within a category, thereby protecting them against identification deficits in the context of category-specific visual agnosia.

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Neurologists and neuropsychologists are aware that aging men are more at risk than women for brain damage, principally because of the well known male-predominant risk for cardiovascular disease and related cerebrovascular accidents. However, a disproportion in prevalence of brain damage between the sexes in childhood may be less suspected. Furthermore, sex-specific risk for other aetiologies of brain damage may be little known, whether in the pediatric or adult populations. Proposals of a sex difference in cognitive recovery from brain damage have also been controversial. Six hundred and thirty five “consecutive” cases with cortical focal lesions including cases of all ages and both sexes were reviewed. Aetiology of the lesion was determined for each case as was postlesion IQ. Risk was highly male prevalent in all age groups, with a predominance of cardiovascular aetiology explaining much of the adult male prevalence. However, several other aetiological categories were significantly male prevalent in juveniles (mitotic, traumatic, dysplasic) and adults (mitotic, traumatic). There was no sex difference in outcome (i.e., postlesion IQ) of these cortical brain lesions for the cohort as a whole, after statistical removal of the influence of lesion extent, aetiology and presence of epilepsy. Mechanisms potentially responsible for sex differences in prevalence, aetiology of brain damage, and recovery, are reviewed and discussed.

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Actions produced in response to familiar objects are predominantly mediated by the visual structure of objects, and less so by their semantic associations. Choosing an action in response to an object tends to be faster than choosing the object's name, leading to the suggestion that there are direct links between the visual representations of objects and their actions. The relative contribution of semantics, however, is unclear when actions are produced in response to novel objects. To investigate the role of semantics when object-action associations are novel, we had participants learn to use and name novel objects and rehearse the object, action, and name associations over one week. Each object-action pair was associated with a label that was either semantically similar or semantically distinct. We found that semantic similarity only affected action and name production when the object associations were novel, suggesting that semantic information is recruited when actions are produced in response to novel objects. We also observed that the advantage to producing an action was absent when associations were novel, suggesting that practice is necessary for these direct links to develop.