Perception and recognition of photographic quality facial caricatures: Implications for the recognition of natural images

Abstract

The perception and recognition of photographic images of famous faces was compared with the same images transformed to produce caricatures of different degrees of exaggeration. Following Brennan (1982; 1985). caricatures were produced by first comparing the position of facial features in a frame-grabbed image with the average position for a series of faces; deviations from the average were then accentuated by a constant fraction (16, 32 or 48%). Photographic quality caricatures for seven famous faces were generated by distorting regions of the original images in accordance with the change in feature positions. Images reducing the distinctiveness of faces (anticaricatures) were produced by decreasing deviations from the norm. In Experiment 1, perceptual ratings of the degree to which images resembled the individuals depicted was found to vary with the degree of caricaturing (−32, −16, 0, +16, +32%). Interpolation from the data indicated that the best likeness occurred for images with a small degree of positive exaggeration (+4.4% on average). The magnitude of this caricature advantage correlated with the familiarity with the target faces and with the quality of the caricaturing proccss as assessed independently by caricature artists. Experiment 2 examined the recognition of normal and caricatured images in a namdface matching task. Overall, the subjects' fastest reaction times occurred for images with positive caricaturing. The caricature advantage was primarily attributed to improved performance on trials where the name and face did not match. The results suggest that both the precise metric proportions of faces and the way faces deviate from average are represented in memory. The results also indicate that the “super-fidelity” of caricatures found (Modes, Brennan & Carey, 1987) is not restricted to line drawings and may, therefore, have implications for how we recognise natural facial images. SUMMARY OF RESULTS Experiment 1 Perceptual ratings of the degree to which images resembled depicted individuals was found to vary with level of caricaturing. Interpolation indicated the best likeness would occur with a small degree of positive caricaturing (+4.4% on average). The magnitude of the caricature advantage at the perceptual level correlated with the familiarity of the faces and with the quality of the caricaturing process as judged by caricature experts. Experiment 2 Overall analysis of the degree of image manipulation producing the fastest reaction times for individual subjects revealed a caricature advantage. This increased speed of processing for caricatured images did not reflect any speed-accuracy trade-off. Caricaturing images can therefore produce more efficient processing in a task requiring matching of a person's face and name. In the overall analysis of variance of reaction times (containing match and non-match trials), the caricature advantage did not achieve statistical significance. Three factors might have contributed to the lack of effect. First, the caricature advantage was relatively small in magnitude amounting to a 3% increase in speed. Secondly, the amount of caricaturing producing optimal speed of processing varied across subjects, some performing best with +16% caricatures, others with +32% caricatures. Finally, and of more theoretical interest, the effects of caricaturing appeared to depend on the type of trial. There was no caricature advantage on congruous trials when the name matched the subsequently presented face image. The caricature advantage was prevalent, however, on incongruous trials where the face and name did not match. With non-match trials, + l6% caricatures were processed significantly faster than the veridical images. Again the increase in speed of processing was not an artefact produced by a speed-accuracy trade-off.