**3. Intermodal conflict in category learning and transfer**

This experiment addressed whether categories can be learned when the objects, simultaneously explored visually and haptically, were actually different although from the same category. Following each study block, the subject was tested by presenting the study objects either visually, haptically, or both visually and haptically. This was repeated four times, followed by a transfer test similar to that used in Experiment 1.

One hypothesis is that cross-modal conflict should retard learning, because of the inconsistency of information available during study. Alternatively, presenting information that is available to both modalities, even when in conflict, could provide additional cues for learning. Since subjects were not told that the objects would be different, and since the differences among the patterns belonging to the same category were not strikingly obvious and encoded by different modalities, it is possible that the visually sensed and felt information for a given 'stimulus' might be integrated into a coherent percept. Since the features encoded visually and haptically could differ, at least for some percentage of the encoded features (Miller, 1972), any integration from the two modalities could, in principle, result in a more robust concept.

Alternatively, the subject could learn two versions for each category, one visual and one haptic, with integration between the modalities playing no role. It is worth stressing that the objects studied visually and haptically for each category were identical; only the pairing on each study trial was inconsistent. Since learning more categories has been found to retard learning but enhance later transfer (Homa & Chambliss, 1975), the formation of multiplemodality categories would predict that learning rate would be slowed by this manipulation but produce more accurate later transfer.

Haptic Concepts 13

On the recognition, test, the overall hit and false alarm rates were .794 and 533, respectively, which demonstrated that subjects discriminated old from new objects on the transfer test. The best discrimination occurred when recognition was tested visually (P(Hit) = .860, P(FA) = .532), or when both haptic and visual information were available (P(Hit) = .819, P(FA) = .468); when tested by the haptic modality alone, the difference between hits and false alarms remained significant but the level of discrimination was reduced (P(Hit) = .702, P(FA) = .600). A post-hoc Bonferronni test revealed that recognition discrimination was ordered V+H = V > H. Discrimination between old and new objects was also enhanced by systematic presentation during study, P(Hit) = .791 and P(FA) = .502; following random

Fig. 6. Mean learning rate across trial blocks under conditions of cross-modal conflict

Classification errors were again rare, averaging between 2% on the immediate test following systematic training and visual testing to 11.0% on the delayed test following random

Inter-modal conflict neither retarded learning nor degraded recognition. In fact, learning was speeded slightly by intermodal conflict, with learning rates comparing favorably to those obtained in any of the conditions in Experiment 1. Similarly, classification and later recognition was largely unperturbed by this manipulation. The results do show clear dominance by the visual modality, since recognition accuracy for touch alone, following learning with both modalities present, was significant but substantially reduced relative to recognition based on vision alone or when both vision and haptic information was available. This would suggest that, when both visual and haptic information are simultaneously available in the learning of concepts that the resulting concepts are biased by visual information, with haptic information available but playing a reduced role. Finally, as was

**3.4 Discussion** 

training and a haptic test.

presentation, these values were P(Hit) = .796 and P(FA) = .565.

On the transfer test, subjects were either provided with the objects to be recognized and classified, based only on its visual appearance, from touch alone, or with both vision and touch provided. As was the case in learning, when an old object was presented to both modalities, the object matched its training pairing. Finally, as was the case in Experiment 1, objects were learned in a systematic or random manner, with testing occurring either immediately or after a delay of one week.
