Eye Behavior During Multiple Object Tracking and Multiple Identity Tracking

Abstract

We review all published eye-tracking studies to date that have used eye movements to examine multiple object (MOT) or multiple identity tracking (MIT). In both tasks, observers dynamically track multiple moving objects. In MOT the objects are identical, whereas in MIT they have distinct identities. In MOT, observers prefer to fixate on blank space, which is often the center of gravity formed by the moving targets (centroid). In contrast, in MIT observers have a strong preference for the target-switching strategy, presumably to refresh and maintain identity-location bindings for the targets. To account for the qualitative differences between MOT and MIT, two mechanisms have been posited, a position tracking (MOT) and an identity tracking (MOT & MIT) mechanism. Eye-tracking studies of MOT have also demonstrated that observers execute rescue saccades toward targets in danger of becoming occluded or are about to change direction after a collision. Crowding attracts the eyes close to it in order to increase visual acuity for the crowded objects to prevent target loss. It is suggested that future studies should concentrate more on MIT, as MIT more closely resembles tracking in the real world.

Effectiveness of “rescue saccades” on the accuracy of tracking multiple moving targets: An eye-tracking study on the effects of target occlusions

“…Obtaining a set size effect despite a similar number of occlusions in the OB-2, OB-4, OC-2, and OC-4 conditions is due to an increase in the frequency of target visit by increasing set size. This is in line with previous research, which showed that observers frequently switch fixations between each target and the centroid of multiple targets during multiple object tracking (MOT), so that there are more saccades to targets as the set size increases (Hyönä et al, 2019).…”

“…According to the literature, even 2-year-old infants are able to track more than one moving object (Cheng et al, 2019), and this ability improves as they grow older. In cognitive science, MTT experiments are used to study behavioral and/or neural aspects related to dynamic attention, short-term memory, and eye movements (for reviews, see Hyönä et al, 2019;Kamkar et al, 2020;Meyerhoff et al, 2017).…”

A hidden Markov model for analyzing eye-tracking of moving objects

“…For example, the Gaussian emission distribution can be easily generalized for non-elliptical objects. The model might even be adaptable to a multiple object tracking setting by using centroids of sets of objects rather than the objects themselves Seiffert, 2008, 2010;Hyönä et al, 2019).…”

“…As noted previously, this may require introducing additional states in the HMM corresponding to subsets of visible objects. Extensive research in the multiple object and multiple identity tracking paradigms suggests that gaze may be concentrated around the centroid of the tracked objects, with occasional looks to the individual tracked objects (Hyönä et al, 2019). This could be incorporated into the HMM by adding a state whose emission distribution is Gaussian around the centroid, or a mixture of a Gaussian around the centroid and Gaussians around the individual objects.…”

Multiple-target tracking in human and machine vision

“…Analyzing the eye movements of the subjects helps better investigate this; if MOT is a parallel mechanism, the subjects should rarely look at the targets, while if MIT is a serial mechanism, subjects should focus on targets one after another. Recently, a review of eye behavior studies for both MOT and MIT is provided in [35].…”