Face processing in photographic identity documents

Photographic identity documents (ID) are widely used to prove the bearer’s identity. In classic laboratory experiments, face images are mostly presented in isolation against a white background, while real life photo-ID checks normally compare a face embedded in a document with the holder. Researchers have begun to ask whether this additional document context might affect face matching. Recent research shows that in face matching tasks, embedding faces into passports introduces a response bias, such that viewers are more likely to accept two pictures as showing the same person. The experiments in this thesis examine the cause of this bias, and whether it generalises to other face processing tasks. In the first three experimental chapters (Chapter 2, 3 and 4), the bias is replicated using various identity documents (passports, driving licences, and student-ID) and in different face matching conditions (e.g. varying mismatch prevalence and task difficulty). Results show that the bias does not rely on perceived authority of the ID or the isolated processing of document elements. Instead, it seems to occur only in the presence of both card background and personal information, which converge in photo-ID. The document-induced bias is specific to unfamiliar faces, and occurs in face matching tasks where the documents themselves are task-irrelevant. Chapters 5 and 6 examine the locus of the document bias, testing both encoding and decisional processes. The effect of documents on memory tasks and first impressions is also examined. The results show that the document-bias seems primarily to affect decision-stage processes. The theoretical and practical implications of these findings are discussed.