Object identification as a function of discriminability and learning presentations: the effect of stimulus similarity and canonical frame alignment on aircraft identification.

Aircraft that were relatively similar (homogeneous) and relatively dissimilar (heterogeneous) in appearance were studied at orientations either consistent (canonical) or inconsistent (noncanonical) with the environmental frame of reference. At test, participants' identification performance was measured with stimuli rotated to novel orientations within the picture plane. During learning and testing, identification of heterogeneous aircraft was better than that of homogeneous aircraft. At test, only identification of homogeneous aircraft revealed a strong linear degradation of performance as angular disparity between the novel test orientations and the original learning orientations increased. During learning and testing, identification was better for aircraft studied at canonical orientations than for those studied at noncanonical orientations. The results are discussed in terms of object identification, aircraft recognition training, categorization, mental representations, and visual mental rotation.