Our aim was to investigate the information used to recognise the human head at a variety of viewpoints. Subjects' task was to identify three familiar people from five different viewpoints. The mean response times depended on the viewpoints of the images. These results suggest that different view-specific information is used at different viewpoints for identification.
Face recognition depends more on internal features of the face such as eyes, mouth, and nose.
Also, the recognition of the back of the head depends more on internal features such as hair colour or hair quality. In contrast, profile recognition might depend just upon external features such as contour or shadow.