How the learning of unfamiliar faces is affected by their similarity to already-known faces

What happens as an unfamiliar face becomes familiar is a process that is poorly understood. Recent evidence suggests that unfamiliar faces are processed in relation to pre-existing face representations. It is proposed that, when a novel face resembles someone whom we already know, the familiar representation is somewhat activated at encoding. Although familiarity has been shown to have a facilitatory effect on novel face recognition, it is unknown how the learning of unfamiliar and ‘similar-to-familiar’ faces differ. To examine this, 91 participants completed a training-test procedure. During training, participants were exposed to multiple arrays containing ambient images of novel ‘similar-to-familiar’ (i.e., UK or American celebrities’ less well-known siblings) and unfamiliar (i.e., Spanish celebrities’ siblings) identities. Exposure duration was also manipulated; training arrays were presented for either 60s or 120s. Following each training array, participants provided an estimate of the total number of identities present. At test, participants were required to make binary ‘familiar’/’novel’ judgements to previously unseen target and distractor images; d' scores were calculated for each participant. Results revealed that identity estimates followed a decreasing linear trend across training trials; although participants become significantly more accurate over time, this trend did not vary as a function of familiarity or exposure duration. At test, sensitivity (d') was significantly higher for ‘similar-to-familiar’ faces relative to unfamiliar faces. As expected, there was also a significant effect of exposure duration, where longer encoding durations resulted in better learning. In addition, these main effects were qualified by an interaction; sensitivity was higher for ‘similar-to-familiar’ compared to unfamiliar faces in the long exposure condition but were not significantly different in the short exposure condition. The present findings suggest that ‘similar-to-familiar’ faces are learned more readily than unfamiliar faces, demonstrating that already stored face representations impact how we learn new faces.