The psychology of face construction: Giving evolution a helping hand

Abstract

Face construction by selecting individual facial features rarely produces recognisable images. We have been developing a system called EvoFIT that works by the repeated selection and breeding of complete faces. Here, we explored two techniques. The first blurred the external parts of the face, to help users focus on the important central facial region. The second, manipulated an evolved face using psychologically-useful „holistic‟ scales: age, masculinity, honesty, etc. Using face construction procedures that mirrored policework, a large benefit emerged for the holistic scales; the benefit of blurring accumulated over the construction process. Performance was best using both techniques: EvoFITs were correctly named 24.5% on average compared to 4.2% for faces constructed using a typical „feature‟ system. It is now possible, therefore, to evolve a fairly recognisable composite from a 2 day memory of a face, the norm for real witnesses. A plausible model to account for the findings is introduced

Whole-face procedures for recovering facial images from memory

“…Frowd et al, 2010;. Much is known about how this method accesses facial memory, allowing comparisons to be made between results of the current study and elsewhere (e.g.…”

“…These could be used to change age, weight, masculinity and seven other overall properties of the face. In Frowd et al (2010), composites constructed after a 2 day delay using blur and holistic tools were correctly named with a mean of 24.5% compared to 4.2% for composites where only holistic tools were used (i.e. with non-blurred external features presented in the face arrays).…”

“…It is under these circumstances that identifications arising from feature-based composites tend to be infrequent in police investigations (Frowd, Hancock et al, 2011), an observation supported by laboratory research (e.g. Frowd, Carson, Ness, McQuiston et al, 2005;Frowd, McQuistonSurrett et al, 2007;Frowd et al, 2010;Koehn & Fisher, 1997;Kovera, Penrod, Pappas & Thill, 1997). In fact, many practitioners find it extremely hard to create a composite with witnesses that have poor face recall; also, under these circumstances, UK police guidelines advise against production of a feature-based composite (ACPO, 2009).…”

“…The most likely candidates underlying the benefit of (perceptual) stretch are the individual features, whose likeness is known to positively correlate with composite naming (Frowd, Bruce, Smith and Hancock, 2008), and the region around eyes, in particular the eye spacing, known to be important for recognition (e.g. Diamond & Carey, 1996;Leder & Bruce, 2000;McIntyre, Frowd, Bruce & Hancock, 2010). So, inaccuracies present in both individual features and spacing in the eye region may be reduced with side-on viewing, augmenting recognition.…”

“…Second, masking the external features interferes with processing of the face as a whole to a greater extent than does presenting blurred external features in the face arrays )-which in turn interferes with recognition to a greater extent than does presenting external features intact in the arrays (Frowd et al, 2010). In the current application, this interference is a good thing: when it is maximal (external-features masked), it enables a face constructor to produce identifiable internal features.…”