Phase integration bias in a motion grouping task.

The perception of the direction of global motion depends on our ability to integrate local motion signals over space and time. We examined motion binding using a task requiring integration of relative phase. Observers completed multiple tasks involving clockwise and counter clockwise motion in a stimulus comprising four sets of linearly arranged dots, two moving horizontally and two moving vertically along sinusoidal trajectories differing in phase. Noise jitter was added along the trajectory perpendicular to each dot's motion. The noise acts as a global grouping cue that improves direction discrimination, but surprisingly, the absence of noise causes consistent below-chance performance (Lorenceau, 1996). We explore this phenomenon and subsequently test the hypothesis that observers perceive reverse motion because their representation of the relative phase of the motion components is systematically biased. We employ a number of different objective and subjective measures of motion integration and measure the phenomenon in both younger and older adults. Taken together, the results presented in the current article demonstrate that noise can promote global grouping in the stimulus and that confident, incorrect responses can be observed in the absence of correct global grouping. Generally, the current result raises the possibility that an integration bias could exist in other motion tasks.

Coordinating the interaction between past and present: Visual working memory for feature bindings overwritten by subsequent action to matching features.

The object-file framework forwarded by Kaheman, Treisman, and Gibbs (1992) has been enormously influential in our understanding of how the visual system links together prior visual content with a current input. Although this framework was initially developed to account for the perceptual benefits associated with feature conjunction repetitions, the present series of experiments examines how the core processes of this framework may also help explain behavior in tasks that require explicit remembering of visual information over the short term. Building off our previous work (Fiacconi & Milliken, 2012, 2013), here we introduce a procedure that affords the opportunity to examine the contributions of object-file review processes to both speeded performance and visual short-term memory (VWM) within the same task. Across two experiments we demonstrate a novel coupling between memory accuracy and speeded performance, such that the conditions that promote faster performance also tend to produce better memory, and vice versa. These findings are discussed in relation to the object-file framework and suggest that the object-file review processes known to guide behavior in speeded performance tasks may also have important mnemonic consequences. Together, these findings unite two lines of research to which Anne Treisman made indelible contributions.