Effect of active exploration of 3-D object views on the view-matching process in object recognition.

Harman et al (1999, Current Biology 9 1315-1318) showed that active exploration of novel objects allows faster recognition of these objects than passive viewing. Here, we examined whether active exploration of particular objects can facilitate subsequent view matching of different objects within the same category. In the generalisation phase, participants performed a matching task between two serially presented views of novel paper-clip objects. When the two views were of the same object, these were related by rotation about the vertical or horizontal axis. Subsequently, in the observation phase, participants were presented with another 5 paper-clip objects. One group of participants (active group) actively explored each of the objects for 20 s using a trackball over a limited range (-45 degrees to +45 degrees) of the horizontal axis. The other participants observed a replay of the active exploration of each of these objects by a participant in the active group (passive group) or observed a static view of the objects (still group). Following this observation phase, the generalisation phase was repeated twice for all groups of participants. The active group showed a clear expansion of the generalisation range about the horizontal axis. However, this expansion disappeared when we replicated the experiment using a smaller range of active exploration (-30 degrees to +30 degrees) and the experiment in which the participants observed a rotating object within the range of -45 degrees to +45 degrees. Furthermore, we found a significant improvement in view generalisation about the vertical axis when participants actively explored objects using a turntable over a range in -45 degrees to +45 degrees of the vertical axis. Most importantly, since participants explored different objects from the ones that were used in the generalisation phase, these results cannot be explained by improvement of the encoding process. The present findings therefore suggest that: (i) active exploration facilitates the process of view matching, (ii) this effect depends on the exploration range and rotational axis, and (iii) interaction between motor and visual information is necessary to facilitate the process of view matching.