| Object-based attention refers to faster responses to probes occurring on the same object with the cue than that to probes occurring on other objects,while equating brute distance.The object-based attention in previous studies is all conceptualized in terms of a specific dimension,in space.Whether or not rhythmic structure in temporal sequences can influence the allocation of attention through time is still unknown.De Freitas,Liverence,and Scholl(2014)proposed temporal object-based attention for the first time.They explored a modified two-rectangle paradigm using independently normed rhythmic temporal sequences,structured into phrases,in which the time intervals between cue-same object target and cue-different object target were the same.Detection was speeded when cues and targets both lay within the same rhythmic phrase,compared to when they spanned a phrase boundary,while equating brute duration,suggesting a temporal object-based effect.Although De Freitas et al.(2014)proposed temporal object-based attention for the first time,a series of questions remained to be unresolved.First,the auditory rhythms in De Freitas(2014)can not confirm the universal existence of temporal object-based attention due to higher time resolution for auditory attention.Whether or not temporal object-based effect could be found in the visual sequences is still unknown.Secondly,previous studies have demonstrated that the mechanisms between temporal and spatial attention are independent,at least partially independent.Then what we want to know is whether or not there are differences in the top-down and bottom-up object relationship between spatial and temporal object-based attention.Third,research on the space-time interaction only examined the condition when these two dimentions of attention are consistent,but not in the inconsistent condition.And the previous studies about object-based attention are based on a single dimension(space or time).Whether or not there is a multi-dimensional interaction effect between temporal and spatial object-based attention?Are mechanisms underlying different dimentions of object-based attention independent or partially overlapping?The current study explores the relationship between temporal top-down and bottom-up objects and the relationship between temporal and spatial objects in conditions when they are consistent and inconsistent to explain the mechanisms underlying temporal object-based attention and the interaction between different dimentions of object-based attention.The current study contains a series of ten experiments for three parts.The first part contained four experiments in which we were focusing on whether visual objects could guide attentional allocation in time and whether or not there existed top-down and bottom-up temporal object-based effects.Experimnet 1 verified that the bottom-up objects formed by different colors could induce object-based effect,but the effect was offset by a reversed participants’ expected effect.Basing on Experiment 1,different shapes were superimposed on different colors in Experimnet 2 to increase the strength of the bottom-up object representation.The result showed significant object-based effect.Experiment 3 proposed that the top-down objects formed by idioms could induce object-based effect,but the effect was still covered by participants’expected effect.Basing on Experiment 3,Experiment 4 found significant top-down object-based effect by using more familiar idoms.In part two,we were interested in situations in which concurrently presented top-down and bottom-up objects correspond temporally,and situations in which concurrently presented top-down and bottom-up objects conflict temporally.Experiments 5 and 6 arranged top-down objects and bottom-up objects congruously,the result found that object-based attention was more effective than that in the top down-only or bottom up-only condition under the lower but not the higher strength of object representation conditions.In Experiments 7 and 8,participants were presented with temporally conflicting top-down and bottom-up objects.Response times were faster when target presented within the top-down object compared to the bottom-up object under the lower strength of object representation condition,but this advantage disappeared when we increased the strength of the bottom-up object representation or at the higher strength of object representation condition.Part two of this study indirectly showed that the spatial and temporal object-based attention involved independent,at least partially independent systems.But it can not directly clarify the exact processes of spatial and temporal object-based attention.Thus,part three of this study contained two experiments and was to reveal the interaction between these two dimensions of object-based attention under consistent and inconsistent conditions in the same paradigm.The results of Experiment 9 showed that temporal object-based effect could be found under the conditions of peripherally presenting stimuli,as that in the centrally presenting stimuli conditions.Basing on Experiment 9,the results of Experiment 10 showed spatial object-based effect in the short SOA condition,with the extension of SOA,temporal object-based effect appeared.However,the temporal objects need enough time to maximize the object-based effect,thus,temporal and spatial object-based effects all played a role in the 400 ms SOA condition,and the temporal objects completely replaced the spatial objects in the 600 ms SOA condition.According to the results above,we make conclusions as follows:1.The visual objects could affect the attentional deployment in time as the aural objects.And the visual objects formed by top-down semantics or bottom-up colors and shapes could induce temporal object-based effect when their object representations were strong enough.2.The temporal object-based effects induced by bottom-up and top-down objects could be additive under the condition of lower strength of object representation,but not the condition of higher strength of object representation.This result is consistent with that in space.When participants were presented with temporally conflicting top-down and bottom-up objects,as that in space,the result depended on the comparison of the strength of these two kinds of object representations.3.When we examined the relationship between temporal and spatial object-based attention by putting them in the same paradigm,the spatial object affected the early stage and the temporal object affected the late stage of attentional processes,they had partial overlap at the 400 ms SOA condition.4.Temporal object-based attention can not be explained by the mechanisms of spatial object-based attention.Therefore,we proposed a Dynamic Matching Thoery which indicated that temporal object-based attention is the process by which a driving regularity that exists in an environmental stimulus is paired with an internal driven time window that has variable amplitude periodicities.Greater object representation results in a stronger driving regularity,and then the accuracy of matching between driving regularity and driven time window will be higher,and then resulting in a stronger object-based effect. |
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