2016 年 14 巻 1 号 p. 23-28
A retrospective attention is known that it can enhance an accuracy of only one item within visual working memory, however, it is not clear whether this attention can enhance that of multiple items or not. The previous study showed a null effect of retrospective attention to multiple items (i.e., a limitation of retrospective attention). It assumed that the null effect caused an extra effort to maintain multiple split foci or the retrospective attention cannot enhance multiple items. Present study investigated whether the effort to separate the retrospective attention to multiple items decline the effect of the retrospective attention with a probed-recall paradigm which is assumed more sensitive than that of previous study. Experiment 1 showed that there was a large effect size of single cueing, but there was no difference between a control condition and a double-cue condition where participants needed to distribute attention. However, it detected a weak effect size of attention between the both conditions. It suggested that distributing attention generated the extra effort and load. Then in order to lighten this load, we eliminated ISI between memorized items and attentional cues to use the iconic memory in Experiment 2. As compared with the accuracies in Experiment 1, those in Experiment 2 improved except that in double-cue condition. It was not enhanced by reduction of ISI as well as by the distribution of the attention. This suggested that the attentional effect in double-cue condition decreased due to the load to separate the attention. Thus, to distribute retrospective attention imposes the load and effort. Moreover, it limits the retrospective attention.