| Inhibition of return (IOR) refers to the slowing of a response to a target appearing at a previously attended location, which is a inhibitory phenomenon of spatial selective attention. This inhibitory effect, first described and labeled'inhibition of return'by Posner and Cohen, was said to reflect a reflexive and adaptive shift of psychological mechanism, encouraging orienting towards novel locations not always focusing on previous ones. With the development of related studies in IOR, more attention had been paid to the special groups. At present, researches on individual differences in IOR mainly lied on the differences of varied-age groups, healthy-unhealthy groups, normal-disabled groups, and even good-bad students in their scores, with different magnitude of IOR and time course. Many studies showed that cognitive style (field- dependence/ independence, FDI) was associated with attentional process, that is to say, there are differences in attentional process between field-dependence (FD) and field-independence (FI) subjects. Additionally, IOR was sorted into the category of spatial selective attention, affected by endogenous and exogenous attentional condition. Hence, the purpose here was to study the differences between FD and FI individuals in IOR task, and influence on them when attentional condition is changed.In this study, 3 experiments were performed, with difficult discrimination tasks: Experiment 1 studied the differences between FD and FI individuals in IOR task using varied SOA, which adopted a 2 (cognitive style: FD, FI)×2 (target location: cued, uncued)×5 (SOA: 150 ms, 350 ms, 550 ms, 750 ms, 950 ms) mixed factorial design. Target location and SOA were within-subject variables and cognitive style was between-subjects variable. Experiment 2 studied the influence of endogenous attentional condition on magnitude of IOR in FD and FI individuals, based on the attentional set formed by designing the probability of targets appearing on the cued location, i.e. the effects of cognitive style and attentional set on IOR, with SOA fixed on 750 ms. It adopted a 2 (cognitive style: FD, FI)×2 (target locatin: cued, uncued)×3 (cue validity: low- validity, high-validity, uninformative) mixed factorial design. Cognitive style and cue validity were between-subjects variables and target location was within-subject variable. Experiment 3 studied the influence of exogenous attentional condition on magnitude of IOR in FD and FI individuals, in the situation of exogenous task-irrelevant moving interruption, with SOA fixed on 750 ms. It adopted a 2 (cognitive style: FD, FI)×2 (target locatin: cued, uncued)×2 (interruption condition: interruption, non-interruption) mixed factorial design. Interruption condition and target location were within-subject variables and congnitive style was between-subjects variable.The results indicated: (1) Time course of IOR in individuals of different cognitive style was significantly different. The time course of IOR in FI subjects are earlier than that in FD subjects. (2) Attentional set affected the magnitude of IOR, with the magnitude of IOR in low-validity condition greater than that in uninformative condition, and no IOR in high-validity condition but facilitation. In uninformative condition, FI subjects inhibited significant IOR effect, whereas FD subjects not. In low/high-validity condition, FI and FD subjects inhibited equivalent magnitude of IOR/facilitation. That was to say, under the influence of attentional set, the difference in the magnitude of IOR between FI and FD subjects no longer existed. (3) The influence of task-irrelevant interruption on the magnitude of IOR was different between FD and FI individuals. FI subjects exhibited significant IOR effect both in the interruption and non-interruption condition, and the magnitude of IOR in each condition was equivalent, whereas FD subjects exhibited IOR effect only in non-interruption condition. That was to say, FD subjects were more affected by task-irrelevant interruption, yet FI subjects were not.
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