![]() ![]() However, decisions can change in the absence of perceptual changes (see, e.g., Morgan et al., 2012). In this scenario, the dissociation of categorical decisions from subjective confidence constitutes evidence for the aftereffect being driven, at least in part, by non-perceptual decision processes.Ĭhanges in decision-making usually constitute acceptable evidence for sensory adaptation. due to a biased pattern of responses when inputs are ambiguous), the range of inputs that elicit low confidence in categorical judgments can remain unchanged, but a dissociation between decision and confidence response profiles can emerge because participants commit to systematically biased categorisations whenever inputs are ambiguous. ![]() However, when decisions change for reasons other than a perceptual change (e.g. When decisions are changed by sensory adaptation, both the decision and confidence functions can provide equivalent measures of the perceptual aftereffect. Recent research suggests that subjective confidence reports can provide an important additional source of information to help discern whether it is probable that an aftereffect has a perceptual basis (Gallagher et al., 2019). While this interpretation is intuitive, there is an equally plausible interpretation: viewing static images that imply movement, or imagining movement, might engage motion-related cognitions that bias categorical decisions, but leave the sensory processes underlying motion perception unchanged (for a related discussion of these issues, see Yarrow et al., 2011). This pattern of results is broadly consistent with the classic motion aftereffect (Barlow & Hill, 1963), and the authors concluded that the adaptation task had directly changed motion perception. In each case the adaptation phase (static images, or imagined motion) gave rise to a negative aftereffect: participants had an increased probability of judging a (possibly ambiguous) stimulus as having moved in the opposite direction. In both studies participants then judged the motion direction of a dynamic dot stimulus. In a second study (Winawer et al., 2010), participants adapted to a static grating and were asked to imagine that it was moving. ( 2008) had participants adapt to still photographs that implied motion (either leftward or rightward, or inward or outward see Fig. Such a method offers an empirical approach to determine if high-level cognitions (such as extracted meaning) can filter down to change perception. However, recent research has started revealing aftereffects in which test stimuli are only conceptually related to the adapting stimulus. Aftereffects are also typically constrained to a common sensory dimension, such as when a moving adaptor influences the perceived motion of a test (Barlow & Hill, 1963). the brightness of lights, or the volume, pitch or frequency of a tone see Clifford et al., 2007, for a review). Usually, perceptual aftereffects are quantified by giving people prolonged and repeated exposure to a specific stimulus, and then measuring changes in response to a range of stimulus intensities (e.g. Our results suggest the implied motion aftereffect produces a bias in decision-making, but leaves perceptual processing unchanged.Īn outstanding question in perception research is whether our thoughts, desires, emotions, or cognitions can change how our sensory systems operate. In Experiment 2 (real motion), we find equal changes to decisions and confidence. In Experiment 1 (implied motion), we find support for decision-level changes only, with no change in subjective confidence. We therefore used subjective confidence as an additional measure of the implied motion aftereffect. Since both categorical decisions and subjective confidence are informed by sensory information, confidence can be informative about whether an aftereffect probably results from changes to perceptual or decision processes. Equally possible, however, is that inferred motion changes decision processes, but not perception. ![]() This finding could indicate that inferred motion direction can penetrate sensory processing and change perception. Viewing static images depicting movement can result in a motion aftereffect: people tend to categorise direction signals as moving in the opposite direction relative to the implied motion in still photographs. ![]()
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