Contextual and Anchoring Effects on Perceptual Resolutions and Perceived Magnitudes: Within- and Between-Modalities Effects

The perception of magnitude, a crucial ability for a mental representation of the physical world, is often not veridical but subject to significant biases. Many of these biases are similar across different sensory modalities, implying a generalized magnitude perceptual system. At the same time, different physical quantities might also have a specialized representation that is modality specific. To shed light on this question of common versus distinct processes in magnitude representation, the present study examined between- and within-modalities contextual effects on perceptual resolutions of magnitudes. In a constant stimuli procedure, a central standard was embedded within shorter and longer contextual standards. These contextual standards were sampled from either a relatively wider or narrower range of durations. Participants were required to determine which of the two consecutive durations was longer. In half of the trials the standard was presented first, creating stronger anchoring. A full within-subject design was applied, in which 12 participants completed 8 experimental combinations of visual and auditory modalities, within- and between-modalities context, and narrow and wide ranges. In each, a full individual psychometric function was fitted, with JNDs indicating perceptual resolutions and PSEs indicating perceived durations. Better perceptual resolutions were found for narrower context, with stronger contextual effects for trials in which the standard was presented first (anchoring effects). Consistent with Bayesian account of magnitude perception, contextual effects were stronger in the visual modality where thresholds were elevated. Time-order effects were also found on the perceived duration so that durations were perceptually underestimated for standard-first trials but overestimated for standard-second trials. Interestingly, narrower context enhanced resolutions of standards of within the same modality but failed to show any effect on standards of the other modality. These results suggest a specialized calibration mechanism of contextual effects on perceptual resolutions that is modality-specific.