The Effects Of Stimulus Uncertainty On Category-specific Attentional Orientin

As a fundamental component of attention system,attentional orientation refers to the ability of selectively allocate attention to task-related visual fields.The attentional orientation plays an important role on the efficient orientation for objects in our daily life.previous studies had improved that the attention can be directed to task-relevant objects by an attentional template.When the target was defined by a set of objects(i.e.,category),a category-specific attentional orientation(CAO)could be generated and guide attention to the task-relevant category efficiently.In addition,uncertainty in stimuli is an inherent feature of perception.Expectation is a kind of uncertainty influenced by prior background information and reflects the readiness to react the upcoming stimulus,which involve in the top-down processing.perceptual load is another kind of uncertainty influenced by the amount of sensory information relevant to the current task,which involve in the bottom-up processing.However,the mechanism and the time course of expectation and perceptual load during the process of CAO,and whether the relationship between these two forms of uncertainties are independent or not remain unclear.To investigate the mechanism and the time course of expectation and perceptual load on the process of CAO across different dimensions,the present study employed a task combining associative learning with visual searching tasks by using ERPs.Color categories(Experiment 1:cold color,warm color)and shape categories(Experiment 2: ’X’-shaped,’O’-shaped)were defined as target.To avoid the effects of spatial attention,sound cues at 1500 Hz and 1000 Hz were used to form a certain anticipation for the target’s position(left or right).In order to control the practice effect,the position of the sound cue in relation with the target was varied between blocks.An expectation task was set up after the sound cue appeared and participants were required to make predictions about the target’s upcoming position so that participants will form a preparation for the target.The homogeneity of the distractors were varied within the category to control the level of perceptual load.EEG indicators were P1,reflecting early attentional capture,and N2 pc reflecting target orientation.The results of reaction times showed an interaction between expectation and perceptual load in both color and shape experiment,F(1,52)= 7.838,p = 0.007,η2 = 0.131,and the simple analysis showed an increased effect of CAO through the decrease of uncertainty(valid and low perceptual load position).As for the ERP results,there was an interaction between anticipation and category dimension,F(1,52)= 6.803,p = 0.012,η2 = 0.116.When the target was defined as shape category,the N2 pc amplitude was larger under the invalid condition,relative to the valid condition.The results of present study indicated that expectation and perceptual load both had independent effects on CAO during the early stage,as measured by N2 pc activity.In the late response stage,these two uncertainties could integrate into together to ensure individuals to make proper performance.The present study provided a basis for the category information processing and the theory of CAO for dealing with uncertainty in daily life.