Learning to discriminate face views 1

25 Although perceptual learning of simple visual features has been studied extensively and 26 intensively for many years, we still know little about the mechanisms of perceptual learning of 27 complex object recognition. In a series of seven experiments, human perceptual learning in 28 discrimination of in-depth orientation of face view was studied using psychophysical methods. We 29 trained subjects to discriminate face orientations around a face view (i.e. 30°) over eight daily sessions, 30 which resulted in a significant improvement in sensitivity to the face view orientation. This improved 31 sensitivity was highly specific to the trained orientation and persisted up to six months. Different from 32 perceptual learning of simple visual features, this orientation-specific learning effect could completely 33 transfer across changes in face size, visual field and face identity. A complete transfer also occurred 34 between two partial face images that were mutually exclusive but constituted a complete face. 35 However, the transfer of the learning effect between upright and inverted faces and between a face and 36 a paperclip object was very weak. These results shed light on the mechanisms of the perceptual 37 learning of face view discrimination. They suggest that the visual system had learned how to compute 38 face orientation from face configural information more accurately and that a large amount of plastic 39 changes took place at a level of higher visual processing where size-, location-and identity-invariant 40 face views are represented.