The Study On Mechanism Of Time Course Of Inhibition Of Return

Location-based inhibition of return (IOR) refers to a slowed response to a targetappearing at a previously attended location. Since Posner and Cohen (1984) observed the IOReffect, there are a lot of studies that focus on the factors underline the time course of IOR,why the time course of IOR in discrimination tasks IOR time was later than the time course ofIOR in detection tasks is one hot issue. Early theory of Re-orienting hypothesis suggests thatattention disengaged early in detection tasks than in discrimination tasks, so IOR effect appearlater. Three hypothetical effects which based on object file suggests that time course of IOR isdetermined by spatial orienting benefit, onset detection cost and spatial selection benefit,attentional resources influence the onset detection cost and spatial selection benefit, becauseprocessing discrimination tasks target need more attentional resources than processingdetection tasks target, time course of IOR is delayed. The current study is aim to usecombining experimental paradigm of IOR and flanker interference and perceptual load, andexamine attentional resources processing in discrimination tasks suggested as threehypothetical effects theory.Study one explored whether the time course of IOR influenced by an irrelevant stimulusand a flanker interference. In experiment1, an irrelevant stimuli presented at ether the thecentral fixation position location or the location opposite to the target position. Resultsshowed that IOR in discrimination tasks was significant at400ms when irrelevant stimuluswas present, the time course was significantly earlier than the results of previous studies, inwhich IOR appear around the700ms in discrimination tasks. In experiment2, flankerinterference paradigm and IOR paradigm were combinated, interference stimulus werepresent outside the target box, results showed that when peripheral interference and target wasincompatible, the facilitatory effect was significant and IOR disappeared, these results did notaccord with the view that discrimination task needs more attention resources proposited bythree hypothetical effects.The aim of study two was to investigate whether the time course of IOR influenced byseveral irrelevant stimulus, experimental paradigm of IOR and perceptual load werecombined. In experiment3, different interfering stimulis and target appeared at one of the twopotential target locations, result showd that facilitatory was significant in all the SOA(400ms,1000ms). Whereas in Experiment4and Experiment5, the target and interference arepresented in four different target potential position, IOR was found significantly only inExperiment4at1000ms of low perceptual load, there were no significant IOR or facilitatoryin other experimental conditions. Results of study two were consistent with the review thattarget discrimination tasks processing requires more attentional resources affecting the IOReffect, but the different results trends in Experiment3and Experiment4,5could not beexplained.Using the Go-NoGo tasks and the letter discrimination tasks, Experimental paradigm ofIOR and perceptual load and perceptual load were combined in study three, which couldpresent a more reality scene closer to our life.The target and and various unrelated stimuliwere present in the search scene simultaneously, subjects were asked to search the target in the scene, and to ignore interference stimulus outside the scene. Results showed that, underthe condition of high perceptual load, IOR effect were not significant in two experiments. Butthe results were not consistent under the condition of low perceptual load condition. IOR wassignificant at short SOA(400ms) of low perceptual load when interference and the target wereconsistent in Experiment6, and IOR disappeared at long SOA (1000ms). In experiment7,IOR was significant at900ms and1400ms when the relationship of target and interferingstimuli were neutral at low perceptual load. Those results could not be explained by threehypothetical effects, attentional control settings, cognitive control and other cognitiveprocesses were also need to consider when explaining the mechanism of the time course ofIOR effect.Based on the conclusions of this study, although three hypothetical effects have greatadvantages to explain the mechanism of the time course of IOR compared to other theories,but it has some disadvantages, it is difficult to fully explain the complex experimental resultsunder all experimental conditions. When the interference was presented and interference waspresente witn different perceptual load levels, the time course of IOR couldn’t be explainedby attentional resource. When the interference was presented, attentional control settingsinfluence the attentional distribute, then influence the time course of IOR. While, interferenceeffect of different perceptual load, especially the low perceptual load was influenced by thecognitive control of subjects. Three hypothetical effects are emended to four hypotheticaleffects, including spatial orienting benefit, onset detection cost, spatial selection benefit andtop-to-down tasks need. Only other top-to-down factors, such as attentional control settings,cognitive control and other cognitive processes were considered, the complex experimentalresults change by experimental conditions can be explained.