These studies showed that serial dependence was present even when the target feature had not been reported on the previous trial, suggesting that serial dependence can be produced by the mere encoding of the previous-trial stimulus. Some studies, however, have included a condition in which no explicit response was required on some trials, which could potentially unconfound the perception and report of the target feature (Czoschke, Fischer, Beitner, Kaiser, & Bledowski, 2019 Fischer & Whitney, 2014 Suárez-Pinilla, Seth, & Roseboom, 2018). Most previous studies of serial dependence required participants to report a single target feature dimension on every trial, which confounds the perception of this feature with the report of the feature. Together, these findings indicate that postperceptual processes play a critical role in serial dependence and that the mere encoding of the previous-trial target is not sufficient to produce the serial dependence effect. When we used the same response modality for both motion and color reports in Experiment 3, we found significant serial dependence effects following both color-report and motion-report trials, but the effect was significantly weaker following color-report trials. Experiment 2 confirmed that this pattern of results was not driven by the difficulty of the color task. In Experiment 1, we found a serial dependence effect for motion only when participants had reported the direction of motion on the previous trial, and not when they had encoded the direction of motion but reported the color of the stimulus. We assessed serial dependence for motion perception as a function of which feature dimension had been reported on the previous trial. The to-be-reported dimension was indicated by a postcue after stimulus offset, so participants were required to encode both features of every stimulus. To distinguish between these possibilities, we designed a task in which participants reported either the color or the direction of a set of colored moving dots on each trial. In the present study we asked whether encoding the previous-trial stimulus is sufficient to produce this serial dependence effect, or whether the effect also depends on postencoding processes. SERIAL VISION ADALAH TRIALThis suggests a reinterpretation of these and perhaps other studies that use the Treisman visual search paradigm, in terms of perceptual segregation of the visual field by disparity, motion, color, and pattern features such as colinearity, orientation, lateral separation, or size.The reported perception of a visual stimulus on one trial can be biased by the stimulus that was presented on the previous trial. However, practice has a significant effect upon the results, indicative of a shift in the mode of search from serial to parallel for all conjunctions tested as well as for single features. Conversely, reaction times for detection of conjunctions of vernier offsets and orientation, or lateral separation and each of the other positional judgements, were related linearly to the number of distractors, suggesting serial search. The initial results showed that reaction times for visual search for conjunctions of stereoscopic disparity and either vernier offsets or orientation were independent of the number of distracting stimuli displayed, suggesting that disparity was searched in parallel with vernier offsets or orientation. A study is reported in which visual search for suprathreshold positional information-vernier offsets, stereoscopic disparity, lateral separation, and orientation-was examined. The nature of the processing of combinations of stimulus dimensions in human vision has recently been investigated.
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