Attention Refresh Units In Multiple Identity Tracking: Object Or Boolean Map?

In everyday life,people often have to tracking multiple distinct targets.The multiple identity tracking paradigm(MIT)is a classic approach to investigate dynamic attention.Previous theoretical models regards of MIT have all assumed that observers need continuously attentional refreshing when targets’ position changing all the time.This means updating the targets’ position and identity representations in visual working memory.Although many MIT studies assumed that objects are the refreshing units,there is currently no research to verify this assumption.Based on the object-based theoretical perspective,different features on an object can be accessed by attention simultaneously.In contrast,the feature-based Boolean map theory suggests that attention can simultaneously access multiple locations,but only one feature value can be accessed at a time within a feature dimension.However,this theoretical perspective has not been validated in the context of dynamic tracking.This study investigates whether objects or Boolean maps can serve as the refreshing units in a multiple identity tracking task,and explores the relationship between the two in this task by manipulating whether multiple probe stimuli belong to the same object or Boolean map.The study consists of three sub-studies,including three experiments in total.Study 1: Investigating whether the Boolean map effect exists in MIT.In experiment 1,36 participants were recruited and a single-factor within-subject design was adopted,with four conditions: two probe stimuli belonging to(1)two same-Boolean-map targets;(2)two different-Boolean-map targets;(3)one target and one distractor;and(4)two distractors.The results showed that the accuracy of probes belonging to the same-Boolean-map(i.e.,having the same feature)was significantly higher than that of probes belonging to different-Boolean-maps(i.e.,having different features).This indicates the existence of a tracking mechanism with Boolean map as the refreshing unit in MIT tasks.Study 2: Investigating whether the same-object effect exists in MIT.In experiment 2,36 participants were recruited and a single-factor within-subject design was adopted,with four conditions: two probe stimuli belonging to(1)the same object;(2)different objects;(3)one target and one distractor;and(4)two distractors.The results showed that the accuracy of the probes belonging to the same object was significantly higher than that of probes belonging to different objects.This indicates the existence of a tracking mechanism with object as the refreshing unit in MIT tasks.Study 3: Investigating the relationship between the Boolean map effect and the object effect in multiple identity tracking.In experiment 3,36 participants were recruited and a single-factor within-subject design was adopted,with four conditions:three probe stimuli(1)with the same-object and same-Boolean-map relations,(2)with only the same-object relation,(3)with only the same-Boolean-map relation,and(4)have neither the same-object nor the same-Boolean-map relation.The results showed that(1)the Boolean map effect and the object effect were significant,(2)there was no significant difference between the Boolean map effect and the object effect,and(3)there was no significant interaction between the Boolean map effect and the object effect.This indicates that the object-based and Boolean map-based mechanisms can coexist in MIT tasks,and the relationship between the two is independent of each other.Conclusion: Both Boolean map and object can serve as refreshing units for multiple identity tracking,and both can coexist in the task independently.