The Face-Race Lightness Illusion Is Not Driven by Low-level Stimulus Properties: An Empirical Reply to Firestone and Scholl (2014)

Abstract

Levin and Banaji (Journal of Experimental Psychology: General, 135, 501-512, 2006) reported a lightness illusion in which participants appeared to perceive Black faces to be darker than White faces, even though the faces were matched for overall brightness and contrast. Recently, this finding was challenged by Firestone and Scholl (Psychonomic Bulletin and Review, 2014), who argued that the nominal illusion remained even when the faces were blurred so as to make their race undetectable, and concluded that uncontrolled perceptual differences between the stimulus faces drove at least some observations of the original distortion effect. In this paper we report that measures of race perception used by Firestone and Scholl were insufficiently sensitive. We demonstrate that a forced choice raceidentification task not only reveals that participants could detect the race of the blurred faces but also that participants' lightness judgments often aligned with their assignment of race.

The "face race lightness illusion": An effect of the eyes and pupils?

“…Firestone and Scholl [ 27 , 28 ] introduced this account, as a case study within a more general discussion about “cognitive penetrability” in perception or top-down cognitive biases. By showing degraded (blurred) versions of the original images, they found that participants continued to yield the same bias, despite being unable to categorize the stimuli as either ethnicity (but see [ 29 ] for a rebuttal). Most interestingly, Firestone and Scholl hinted at the possibility that spontaneous patterns of eye movements on such salient features could be at the basis of the response bias and explicitly stated that a face could look darker if gaze or attention was captured by its salient dark parts.…”

Contextual Effects in Face Lightness Perception Are Not Expertise-Dependent

“…While we do not wish to engage in a discussion about whether such an interaction between race assumptions (in terms of the expected surface reflectance patterns) and traditional mechanisms for reflectance computations would constitute a ‘top-down’ contextual influence, we note that such an interaction would be congruent with Baker and Levin [32]’s observations that lightness judgments relate well to observers’ assignments of race categories. Critically, however, if we draw upon speculations underlying other-race effects in the traditional face literature, that is, that such effects manifest in better efficiencies in encoding own-race category faces [40,44,45,46]—then it follows that we should have observed additional expertise-dependent modulations in lightness judgments should the two phenomena be related.…”

“…While our procedures of luminance and contrast normalization should have acted to reduce the saliency of these differences somewhat, they are nevertheless still retained to some degree. Still, we note that in their reply to Firestone and Scholl [31], Baker and Levin [32] used photonegative (luminance-inverted) versions of blurred stimuli (which preserved such spatial heterogeneities across races, albeit inverted), and found that observers no longer judged one face to be lighter than the other (which was the case of judgments for the veridically blurred stimuli). Thus, it seems unlikely that low-level differences alone, and specifically with respect to differences in spatial distribution, could explain the data observed here (and elsewhere; [25,32]).…”

“…We probed the mechanisms underlying contextual effects in face lightness perception. While several groups have shown that context, in the form of race-specifying information, influences perceptual estimations of face reflectance [25,32], it is unknown as to whether these contextual effects are governed by the same classical mechanisms that drive face perception. We exploited well-known expertise-related effects in face recognition (i.e., the other race effect; [42,43]) and asked if comparable mechanisms underlie contextual (race-based) modulations of lightness judgments involving face stimuli.…”

“…They demonstrated that participants, when presented with blurred faces of differing races and, therefore, presumed to have no conscious knowledge of their corresponding race still judged the Black (blurred) face as being darker. They therefore argued that race or social category knowledge must not be the underlying source of the observed distortions of lightness judgments (see, however, a subsequent response by Baker & Levin [32]). Still, it is worth noting that a simple blurring of the faces may retain the more global differences or asymmetries in contrast across races of different faces (due to differences in morphology) which could then lead to contextual influences.…”