Task Relevance Modulates The Necessity Of Visual Attention To Ensemble Perception

In our daily life,redundant and complex visual information is available for us to perceive and attend at any moment.However,only limited information get access to the visual processing system from a glimpse at a scene owing to several factors,such as limited attention resources,limited eye movement and scanning range,scarce visual working memory capacity and other factors.Fortunately,the information contained in a natural scene,though is complicated,is not completely random.Instead,most scenes often contain many similar or clustered objects,features or textures.When faced to many similar objects,visual system is able to perceive their summary statistical information,which is called ensemble perception.Whether the ensemble perception requires attention or not is a controversial and significant theoretical problem in recent years.For this issue,the previous studies almost have used explicit measure to record the participants’ performance,so their results may be influenced by some factors.Hence,we adopted a more objective implicit method to investigate this question.In experiment 1,the two stimuli were both in the task-relevant location,which means they were both in attented location;In Experiment 2,one of the stimuli was placed in the task-relevant location by cue frame wihile the other was in unattented location.According to the category identity effect,people would performe more accurately and faster when the two stimuli belong to the same category than different category.Hence,we compared the participants’ ensemble perception performance in the two experimental conditions.The results showed that,in contrast to attended line groups,when the stimulus was placed in the unattented location and its summary statistical information was unrelated to the target-set,it did not affect the ensemble perception performance of the stimuli within task-relevant locations.On the contrary,when its summary statistical information was related to the target-set,it would influence the participants’ behavior.Consequently,this result indicated that the demanding to attention of ensemble perception was influenced by task relevance.