Categorical Effects in the Perception of Familiar Faces

Abstract

Photographs of morphed faces were shown to close friends of portrayed individuals. Three tasks were used: localisation of a morphed target on the continuum between the two original faces, simultaneous same - different discrimination of face pairs separated by a 20% morphing step (AB task), and sequential classification of the same pairs (ABX task). Localisation data were plotted against morph coefficients. Evidence of categorical processing was provided by steeper functions for upright vs upside-down faces. In the AB task, intermediate faces were discriminated better than faces separated by the same morphing step but closer to one original. This was confirmed in a control experiment where the participants were unfamiliar with portrayed individuals and were unlikely to process our stimuli categorically. The superiority of intermediate faces in the AB task was attributed to a nonlinearity of continua generated by the morphing procedure, and used as a baseline to evaluate ABX classification data. Also in the ABX task, intermediate faces, those straddling the categorical boundary, were classified more accurately than faces located on the same side of the boundary. However, the superiority in classification accuracy was larger than the superiority in discrimination accuracy operationalised by the AB task, as predicted by the categorical perception hypothesis.

Face Familiarity, Distinctiveness, and Categorical Perception

“…The familiar faces used in Experiment 1 are clearly typical faces, and Angeli (2004) reasoned that this might be important. Pursuing the possibility of categorical effects with unfamiliar faces, what looked like CP was found on one continuum out of the several examined for that effect.…”

“…Furthermore, they claim from their data that CP would be easily found for any novel stimuli including inverted faces. Subsequent work (Campanella et al, 2003;Angeli, 2004;McKone et al, 2001) has been unable to repeat that finding for inverted faces, and this is not further discussed. Campanella et al (2003) also claim that the rapid acquisition of CP for unfamiliar faces is hard to explain within Valentine's model of face space organized around the similarity of exemplars (Valentine, 1991).…”