The Caledonian face test: A new test of face discrimination

Abstract

This study aimed to develop a clinical test of face perception which is applicable to a wide range of patients and can capture normal variability. The Caledonian face test utilises synthetic faces which combine simplicity with sufficient realism to permit individual identification. Face discrimination thresholds (i.e. minimum difference between faces required for accurate discrimination) were determined in an "odd-one-out" task. The difference between faces was controlled by an adaptive QUEST procedure. A broad range of face discrimination sensitivity was determined from a group (N=52) of young adults (mean 5.75%; SD 1.18; range 3.33-8.84%). The test is fast (3-4 min), repeatable (test-re-test r(2)=0.795) and demonstrates a significant inversion effect. The potential to identify impairments of face discrimination was evaluated by testing LM who reported a lifelong difficulty with face perception. While LM's impairment for two established face tests was close to the criterion for significance (Z-scores of -2.20 and -2.27) for the Caledonian face test, her Z-score was -7.26, implying a more than threefold higher sensitivity. The new face test provides a quantifiable and repeatable assessment of face discrimination ability. The enhanced sensitivity suggests that the Caledonian face test may be capable of detecting more subtle impairments of face perception than available tests.

Contributions of individual face features to face discrimination

“…This value is in line with results of previous investigations of synthetic face discrimination (Loffler et al, 2005a, Wilson, Loffler & Wilkinson, 2002. For example, Logan et al (2016) reported a range between 3.33 and 8.84% for 52 typical observers.…”

“…Thirdly, a comparable BOLD fMRI signal in the FFA for face photographs and synthetic faces suggests that the brain processes both stimuli in a similar way (Loffler et al, 2005b). Finally, two recent studies (Lee et al, 2010, Logan et al, 2016 identified impairments of synthetic face discrimination in patients with developmental prosopagnosia. In one of them, synthetic faces were employed within a new test of face discrimination (the Caledonian face test; Logan et al 2016).…”

“…Secondly, synthetic faces demonstrate behavioral hallmarks of face processing including a face inversion effect (Logan et al, 2016, Wilson, Loffler & Wilkinson, 2002 and left-over-right visual field bias (Schmidtmann et al, 2015). Thirdly, a comparable BOLD fMRI signal in the FFA for face photographs and synthetic faces suggests that the brain processes both stimuli in a similar way (Loffler et al, 2005b).…”

“…Finally, two recent studies (Lee et al, 2010, Logan et al, 2016 identified impairments of synthetic face discrimination in patients with developmental prosopagnosia. In one of them, synthetic faces were employed within a new test of face discrimination (the Caledonian face test; Logan et al 2016). The synthetic face test, in agreement with two established face tests, identified an impairment of face perception in a case of suspected developmental prosopagnosia, but the test utilizing synthetic faces enjoyed a higher sensitivity than the established tests.…”

Normative data for accuracy and response times at the computerized Benton Facial Recognition Test (BFRT-c)

“…A"perceptual" version of this test, the Cambridge Face Perception Test (CFPT, Duchaine, Germine & Nakayama, 2007), much less widely used, is also associated with a large interindividual variability in performance (Bowles et al, 2009;Duchaine et al, 2007;Garrido, Duchaine, & Nakayama, 2008). However, the CFPT is not based on matching of different individual faces, but rather involves similarity judgments on morphed faces (see also Logan, Wilkinson, Wilson, Gordon, & Loffler, 2016), i.e. a task which is also likely to be highly influenced by higher-level cognitive processes.…”