Eye-witnesses should not do cryptic crosswords prior to identity parades

Navon letter tasks have been shown to affect subsequent face recognition performance. As such tasks are not likely to by carried out prior to a witness attending an identity parade this is unlikely to have much applied relevance. Here, however, it is explored how a range of puzzles that witnesses might engage in affect face recognition. Cryptic crosswords were found to have a detrimental effect on subsequent face recognition, unlike reading, literal crosswords, or sudoku. As well as this finding's practical importance, it also provides a further insight into the Navon effect on face processing. The identification of an offender by a witness to a crime often forms an important element of a prosecution's case. While considerable importance is placed by jurors on the identification of the offender by a witness (such as a suspect being picked out from an identity parade), research tells us that these identifications can often be wrong and sometimes lead to wrongful convictions (eg Rattner 1988). Exploration of factors that improve or produce a detriment in our abilities to pick out correctly a person from an identity parade is of obvious utility. It has been shown that face-recognition performance in an eye-witness-like situation can be influenced by a task immediately preceding the recognition test. Schooler and Engstler-Schooler (1990) demonstrated that describing a face can make a facerecognition task harder, but it has also been shown that describing an unrelated object, such as a car, has a similar effect (Brown and Lloyd-Jones 2003). Macrae and Lewis (2002) and Perfect (2003) have demonstrated that processing Navon stimuli has a profound effect on subsequent face recognition. Navon stimuli are large letters formed from repeating a single small letter. Such a stimulus can be seen as consisting of a global element (the large letter) and local elements (the small letters). If participants read out the large letters of these stimuli, then subsequent face recognition performance was found to be better than controls, but if the participants read out the smaller letters of the same stimuli they did worse than the controls. A similar effect has been found when using Navon shapes rather than letters (eg a large circle made up of small squaresöHills and Lewis, in press). It has been suggested that these two effects described above are similar in their mechanism (Macrae and Lewis 2002). One proposed mechanism is that the tasks detrimental to face recognition (verbal description or the local-letter task) lead to a shift in the way in which faces are processed from a configural manner to a featural manner (eg Schooler 2002). This shift leads to the observed poorer performance. One possible practical application for these findings is that it may be possible to improve a witness's performance in an identity parade by using a simple task before the line up. This possibility, however, assumes that the gain observed between the global-letter task and the control is due to improved performance after the global Navon stimuli rather than a detriment after the control task (which is often a reading task). Consequently, it may be difficult to improve default face-processing ability; however, it appears that there are a number of ways that we can make it worse. Obviously, within a forensic situation it would be undesirable to have witnesses doing something before an identity parade that would make them worse at picking out the offender. Thankfully, it is very unlikely that witnesses encounter Navon stimuli just before an identity parade and even more unlikely that they will read the local letters of those stimuli if they do encounter them. Last but not least Perception, 2006, volume 35, pages 1433 ^ 1436