Serial Dependence in the Perception of Faces

Abstract

Summary From moment to moment, we perceive objects in the world as continuous despite fluctuations in their image properties due to factors like occlusion, visual noise, and eye movements. The mechanism by which the visual system accomplishes this object continuity remains elusive. Recent results have demonstrated that the perception of low-level stimulus features such as orientation and numerosity is systematically biased (i.e., pulled) toward visual input from the recent past [1, 2]. The spatial region over which current orientations are pulled by previous orientations is known as the continuity field, which is temporally tuned for the past 10–15 s [1]. This perceptual pull could contribute to the visual stability of low-level features over short time periods, but it does not address how visual stability occurs at the level of object identity. Here, we tested whether the visual system facilitates stable perception by biasing current perception of a face, a complex and behaviorally relevant object, toward recently seen faces. We found that perception of face identity is systematically biased toward identities seen up to several seconds prior, even across changes in viewpoint. This effect did not depend on subjects’ prior responses or on the method used to measure identity perception. Although this bias in perceived identity manifests as a misperception, it is adaptive: visual processing echoes the stability of objects in the world to create perceptual continuity. The serial dependence of identity perception promotes object identity invariance over time and provides the clearest evidence for the existence of an object-selective perceptual continuity field.

Relative judgment in facial identity perception as revealed by sequential effects

“…Second, when relative information is used as evidence to inform judgment, females tend to assimilate their judgments toward the category of the preceding faces whereas males tend to either assimilate or contrast their judgments toward or away from the category of the preceding faces, depending on the relationship between preceding and current faces. Recent studies also have reported sequential effects in the perceptual judgments of other facial domains, such as face perception (Liberman, Fischer, & Whitney, 2014), facial expression (Hsu & Yang, 2013) and facial attractiveness (Kondo, Takahashi, & Watanabe, 2012Kramer, Jones, & Sharma, 2013). With the present study, these findings suggest the inherent nature of relative judgment in face perception in general.…”

Post-decisional accounts of biases in confidence

“…Such bias has been seen in a low level task, orientation judgement, in which participants' choices were significantly biased toward orientations reported in the previous trials even though the stimuli changed randomly trial-by-trial [33]. It has also been seen in a high-level task, face-perception [34]. In both cases, the effects of post-decisional processing extended to the next trial and modulated subsequent decisions.…”

“…This is assuming that evidence is integrated without bias. However, several studies have shown that post-decisional processing could be biased, and so could distort confidence judgments [17,26,[31][32][33][34]. For example, evidence for the chosen option could be overweighed (i.e., accumulated at a larger rate than the unchosen options as in [31]) leading to an increase in confidence that is not based on objective evidence; this is known as "confirmation bias" [26].…”

“…Other sources of bias include serial dependencies; i.e., conditions in which choices made in the recent past influence upcoming decisions [32][33][34]. Such bias has been seen in a low level task, orientation judgement, in which participants' choices were significantly biased toward orientations reported in the previous trials even though the stimuli changed randomly trial-by-trial [33].…”

“…Finally, serial dependencies (Fig 1-B) can lead to bias in laboratory experiments (where evidence is often independent and identically distributed), but they may be a good strategy in more realistic conditions, where noise is structured differently [33,34]. Because the statistical properties of the physical world are temporally stable (for example, low-level properties in a natural scene do not vary randomly over time, making the past a good predictor of the future), the brain might be tuned to exploit these regularities in the environment.…”