The Influence Of Position Information On Visual Working Memory

In real life,individuals must integrate feature information and position information to direct actions to objects,which is named object-position binding.In theory study,the role of position information in visual working memory is also emphasized.Position information is used to separate objects from one another in the perception and the memorization phases,and as a clue to identify objects in the recognition phase.Previous studies which investigated the role of position information in visual working memory,usually used the single probe paradigm to estimate the influence of position information on recognition of individual objects.In contrast,this research uses the whole probe paradigm to explore the influence of position information on working memory of multiple objects presented stimultaneously,and to investigate whether this kind of influence is affected by the differences in visual fields and predictability of position changes.This paper includes four experiments.Exp1 was designed as 3(set size: 2,4,6 items)× 2(probe: single probe and whole probe)× 2(recognition position: change,no change)three factors within-subjects design.In Exp2,visual field was added as another factor on the basis of Exp1.Subjects were presented with a bilateral array of colored squares and were asked to remember the items in only one hemi-field.So Exp2 was designed as 3(set size: 2,4,6 items)× 2(probe: single probe and whole probe)× 2(recognition position: change,no change)× 2(visual filed: left,right)four factors within-subjects design.In Exp1 and Exp2,colored squares always appeared at the fixed locations when recognition position changed,so position change was predictable.Exp3 was adapted on the basis of Exp1.Colored squares appeared at random locations under the “position change” condition.In addition,only whole-probe paradigm was used in Exp3.Therefore,Exp3 was designed as 3(set size: 2,4,6 items)× 2(recognition position: change,no change)two factors within-subjects design.From Exp1 to Exp3 recognition position conditions were balanced across subtasks,so subjects know whether positions need to be matched in the next task.However,in Exp4,recognition position conditions were balanced within blocks,which meant subjects did not know whether positions in the test array would change in the next trial.Subjects followed the same instruction that they need to tell whether all the colors in the test array are the same as that of the memory array.In Exp4,3(set size: 2,4,6 items)× 2(recognition position: change,no change)two factors within-subjects design was used as Exp3 did.In addition,after subjects finished the visual working memory task in all the four experiments,they were asked to complete a spatial working memory span test.It is found that,(1)The influence of position information on visual working memory is affected by the difference in probe paradigms.Specifically,when the single paradigm is used,recognition position has no effect on memory accuracy.However,Rt of “no-change position” condition is longer than that of “change position” condition.When the whole probe paradigm is used,accuracy of “no-change position” condition is higher than that of the “change position condition” and Rt of “no-change position” condition is shorter than that of the “change position” condition.(2)The influence of position information on visual working memory shows no bias towards left visual field or right visual field.(3)When the whole probe paradigm is used,the influence of position information on visual working memory is not affected by the predictability of position changes.(4)The influence of position information on visual working memory is affected by set size.To be specific,when the set size approaches or exceeds average visual working memory capacity(usually 4 items),position information has a stable influence on visual working memory performance;but when the set size is far less than visual working memory capacity(e.g.,2 items),position information does not certainly affect visual working memory.(5)The influence which the position information has on visual working memory is not affected by individuals' mere spatial working memory capacity.