Recognising Faces Seen Alone or with Others: When Two Heads Are Worse than One AHMED M. MEGREYA and A. MIKE BURTON * University of Glasgow, UK SUMMARY There is a large body of work investigating face identification, but most of this addresses recognition of a single person. Here, we examine how recognition is affected by the presence of a second face. In Experiments 1 and 2, we demonstrate that memory for an unfamiliar face is severely reduced if it is seen alongside a second person. Sequential presentation of two target faces further reduces accuracy. In Experiments 3 and 4, we demonstrate the same disadvantage for two-face targets in a matching task, where subjects have no time limits or memory requirement. In matching, the damaging effect of a second face is greatest when the targets are placed close together. Furthermore, there is a general advantage for faces presented to the left. We suggest that it may not be possible to extrapolate results from single-face studies to experiments (or realistic situations) involving more than one person. Copyright # 2006 John Wiley & Sons, Ltd. Research in person recognition demonstrates that there are multiple processes engaged when we examine a face. Computation of identity (for familiar faces) appears to proceed to some extent in parallel to computation of other characteristics such as facial speech or expression (Bruce & Young, 1986). Furthermore, processes involved in identifying familiar and unfamiliar faces appear somewhat different, as we will discuss below. Studies of basic processes involved in face recognition have been used to understand applied issues, and particularly eye-witness identification. However, there is rather little in the available literature, whether theoretical or applied, on processes involved in viewing several faces simultaneously. This is perhaps surprising. We are very commonly involved in situations where simultaneous identification is necessary (e.g. social situations in a group, or when viewing a TV programme involving several characters). Furthermore, in real-world eye-witnessing situations, there are very often several protagonists. This is the topic for the present paper. We will start by briefly reviewing the pertinent literature in eye- witness identification. We will then consider some recent research on attention and faces which may have some bearing on these issues. We will then present a series of experiments in which we examine recognition of multiple faces. It has been known for many years that eye-witness identification is prone to error (see Cutler & Penrod, 1995; Lindsay & Pozzulo, 1999; Narby, Cutler, & Penrod, 1996; Wells, 1993; Wells, Wright, & Bradfield, 1999; Westcott & Brace, 2002 for reviews). Witnesses to APPLIED COGNITIVE PSYCHOLOGY Appl. Cognit. Psychol. 20: 957–972 (2006) Published online 21 June 2006 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/acp.1243 *Correspondence to: A. M. Burton, Department of Psychology, University of Glasgow, Glasgow G12 8QQ, UK. E-mail: mike@psy.gla.ac.uk Copyright # 2006 John Wiley & Sons, Ltd.