When the World Changes in Your Hands: Similarity Ratings of Objects Morphing during Active Exploration

View-based theories of object recognition posit that coherent object representations are formed by linking together successive views of an actively explored object. This linking process relies on the assumption that the object does not change during exploration. Here, we test how object representations might be influenced when the shape of the object changes slowly during exploration. In our experiment, participants rated the similarity of two novel, 3D objects, whose shape was parametrically defined. Seventeen participants explored each object for 10 sec on an iPad which afforded natural and efficient interaction. The experiment contained a baseline condition, in which two objects of varying parameter-differences were presented, and a morphing condition, in which the first of the two objects slowly morphed during active exploration, making the objects more similar. Interestingly, no participant was aware of this morphing manipulation. Comparing baseline and morph trials, however, we found significantly higher similarity ratings during morphing [F(1,16) = 84.79, p < .001]. Furthermore, correlations between similarity ratings and differences in object parameters were high for the baseline condition (r = −.64), with smaller parameter differences being perceived as more similar. Interestingly, in the morphing condition correlations were lower for parameter differences after the morph (r = −.22), but remained high for differences before (r = −.47) and during morphing (r = −.50). In conclusion, similarity ratings in the baseline condition captured the complex parameter space well. Although participants did not notice the changing shape, morphing did systematically bias the ratings. Interestingly, similarity judgments correlated better in the initial exploration phase, suggesting a capacity limit for view integration of complex shapes