Geneviève Desmarais

A role for action knowledge in visual object identification

We evaluated the impact of visual similarity and action similarity on visual object identification. We taught participants to associate novel objects with nonword labels and verified that in memory visually similar objects were confused more often than visually dissimilar objects. We then taught participants to associate novel actions with nonword labels and verified that similar actions were confused more often than dissimilar actions. We then paired specific objects with specific actions. Visually similar objects paired with similar actions were confused more often in memory than when these same objects were paired with dissimilar actions. Hence the actions associated with objects served to increase or decrease their separation in memory space, and influenced the ease with which these objects could be identified. These experiments ultimately demonstrated that when identifying stationary objects, the memory of how these object were used dramatically influenced the ability to identify these objects.

Understanding the structural determinants of object confusion in memory: an assessment of psychophysical approaches to estimating visual similarity.

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 on object identification in a patient with category-specific visual agnosia

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 ELMs 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.

The importance of object similarity in the production and identification of actions associated with objects

Past research suggests that the similarity between the objects associated with actions impacts visual action identification and action production. Indeed, people often confuse actions that are visually similar, as well as actions that are associated with visually similar objects. However, because the action errors often involve actions that are visually similar and are associated with visually similar objects, it is difficult to disambiguate between the influences of object similarity and action similarity. In our experiments, healthy participants were asked to learn to associate nonword names and actions with novel objects. Participants were first shown each object and its action and were then asked to visually identify each object. In Experiment 1, participants were then asked to produce the action associated with each object, and in Experiment 2, they were asked to visually identify the action associated with each object. Actions were confused more often when they were associated with similar objects than when they were associated with dissimilar objects. Furthermore, following an object naming error, participants were more likely to produce the action associated with the erroneous name than any other erroneous action. The results suggest that the visual characteristics of the objects influenced action production and action identification.

Influences of visual and action information on object identification and action production.

To evaluate the impact of semantic information elicited by labels, participants learned to identify or use novel graspable objects associated with novel actions. We identified each object/action pair with labels that elicited visual form or action semantics and varied the congruence between the labels information and the visual form or action of novel objects. In Experiment 1, participants named objects, and in Experiment 2 they produced the action associated with objects. Generally, congruent labels facilitated performance. Furthermore, for participants who learned incongruent associations, the visual form and semantic information elicited by labels influenced performance in opposite patterns. These findings support the notion that naming may be required before actions are produced when object/action associations are novel. Our findings further support the notion that links between the structural properties of objects and their actions may already be stronger than the links between verbal labels and actions in novel object/action associations.

What’s in a name? The influence of verbal labels on action production in novel object/action associations

ABSTRACT Actions are produced directly from the visual features of objects; object recognition and semantic information are not necessary for action production. However, much of that research has used familiar objects. Recent studies looking at novel object–action associations suggest that semantic information associated with labels used to identify novel object–action pairs can impact action production. Furthermore, the similarity of naming performance and action performance suggests that object recognition may occur prior to action production in response to novel objects. We examined whether naming occurred before action production in four experiments where we asked participants to learn novel object/action/label associations, and produce the action associated with each object. Our results demonstrate that removing labels diminished the impact of object similarity in action production, and are consistent with the notion that labels serve to anchor action information to visual object information during the learning process.

Impact of semantic similarity in novel associations: Direct and indirect routes to action

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.

Adding and omitting components of actions: Differences in salience between pulling, twisting, and sliding

How should we measure improvement after aphasia therapy? A look at the use of social validation Jennifer M. Cupit , Elizabeth A. Rochon , Carol Leonard , Laura Laird a a Department of Speech-Language Pathology, University of Toronto, 500 University Avenue, Toronto, Ont., Canada M5G 1V7 b Toronto Rehabilitation Institute, 550 University Avenue, Toronto, Ont., Canada M5G 2A2 c Audiology and Speech-Language Pathology Program, University of Ottawa, 451 Smyth Road, Ottawa, Ont., Canada K1H 8M5 E-mail address: jennifer.cupit@utoronto.ca (J.M. Cupit)

Visuo-haptic integration in object identification using novel objects

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.

The impact of dementia on apraxia and function in daily living

living Richard Painter , Geneviève Desmarais , Vessela Stamenova , Eric A. Roy , Norman W. Park , David A. Gold , Sabrina Lombardi d a Department of Psychology, Wilfrid Laurier University, 75 University Avenue West, Waterloo, Ont., Canada N2L 3C5 b Department of Kinesiology, University of Waterloo, 200 University Avenue West, Waterloo, Ont., Canada N2L 3G1 c Graduate Department of Rehabilitation Science, University of Toronto, 500 University Avenue, Toronto, Ont., Canada M5G 1V7 d York University, 4700 Keele Street, Toronto, Ont., Canada M3J 1P3 E-mail address: pain5010@wlu.ca (S. Lombardi)