According to cognitive and neurological models of the face-processing system, faces are represented at two levels of abstraction. First, image-based pictorial representations code a particular instance of a face and include information that is unrelated to identity-such as lighting, pose, and expression. Second, at a more abstract level, identity-specific representations combine information from various encounters with a single face. Here we tested whether identity-level representations mediate unfamiliar face matching performance. Across three experiments we manipulated identity attributions to pairs of target images and measured the effect on subsequent identification decisions. Participants were instructed that target images were either two photos of the same person (1ID condition) or photos of two different people (2ID condition). This manipulation consistently affected performance in sequential matching: 1ID instructions improved accuracy on "match" trials and caused participants to adopt a more liberal response bias than the 2ID condition. However, this manipulation did not affect performance in simultaneous matching. We conclude that identity-level representations, generated in working memory, influence the amount of variation tolerated between images, when making identity judgements in sequential face matching.

Community pharmacists in Australia appear to be willing to supply naloxone. Low levels of knowledge about naloxone pharmacology and administration highlight the importance of training pharmacists about overdose prevention.

People are poor at matching the identity of unfamiliar faces, but very good at identifying familiar faces. Theoretical accounts suggest that representations derived from exposure to variation are instrumental in driving this familiarity based improvement. In support of this, recent work shows that providing multiple photographs of an unfamiliar face improves identity verification accuracy. Here, we test whether the extent of variation is critical to this improvement, by manipulating the degree of within-identity variation that participants are exposed to in a sequential matching test. Participants were more accurate and adopted more liberal response criteria, when matching high-variability pairs to probe images, compared with either low-variability pairs or single images. Importantly, benefits of variation are not explained by independent contributions of single images, suggesting that people extrapolate information across images to produce gains in identification accuracy. These results suggest that photo-ID can be improved by incorporating broader ranges of variation in facial appearance.

Familiarity incrementally improves our ability to identify faces. It has been hypothesized that this improvement reflects the refinement of memory representations which incorporate variation in appearance across encounters. Although it is established that exposure to variation improves face identification accuracy, it is not clear how variation is assimilated into internal face representations. To address this, we used a novel approach to isolate the effect of integrating separate exposures into a single-identity representation. Participants (n = 113) were exposed to either a single video clip or a pair of video clips of target identities. Pairs of video clips were presented as either a single identity (associated with a single name, e.g. Betty-Sue) or dual identities (associated with two names, e.g. Betty and Sue). Results show that participants exposed to pairs of video clips showed better matching performance compared with participants trained with a single clip. More importantly, identification accuracy was higher for faces presented as single identities compared to faces presented as dual identities. This provides the first direct evidence that the integration of information across separate exposures benefits face matching, thereby establishing a mechanism that may explain people's impressive ability to recognize familiar faces.

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