Doran, M. M., Hoffman, J.E., & Scholl, B. J. (in press). The role of eye fixations in concentration and amplification effects during multiple object tracking. Visual Cognition.
When tracking spatially extended objects (i.e. Lines) in MOT, attention seems to be preferentially allocated to object centers rather than ends (attentional concentration) and this uneven distribution of attention becomes even more pronounced with increases in object length (attentional amplification). In the current work, we investigated the possibility that coincidental patterns of eye fixations could contribute to concentration and amplification effects. Participants performed simultaneous MOT and probe detection tasks similar to these:
We observed robust concentration (i.e. center probes were detected at higher rates than end probes) when probes were equated based on their distance from the locus of fixation in an experiment in which observers were free to move their eyes. Follow the links below to see typical patterns of eye movements during this task. Note that in these movies, target lines are green and distractor lines are white. Probes that were detected appear in green, and probes that were not detected appear in red. The participant’s locus of fixation is plotted as a gray circle and the “center of gravity” of the targets is plotted as a red box. In the actual experiment, all tracking objects (targets and distractors) were white, all of the probes were gray, and the center of mass and fixation markers were not present.
Observers often fixated different objects in the display:
Observers often looked at the center-of-gravity of the targets: