Identity categories and transformational paths for face changes across the age spectrum.

How faces change across lengthy time periods and whether the changing appearance of a face functions as an identity category was investigated in two experiments. In Experiment 1, the faces of 15 individuals were multidimensionally scaled at each of seven age epochs (roughly <6 months to 75 years of age) and correlated with the same persons, but at different ages. In Experiment 2, three individuals at each of seven age epochs were multidimensionally scaled, and analyses explored the conceptual structure and transformational path of each person within the space. The results revealed that even the earliest age epochs (<6 months) were correlated with the later epochs, except for the most extreme age, with the correlation highest at intermediate ages. Transformational paths were found that emerged and terminated at haphazard points in the space. Results are discussed in terms of principled change in categories whose members systematically change across their life cycle, including suggestions for the need to incorporate systematic change in current theories of categorization.