The Influence Of Retinal Eccentricity On The Gradient Distribution Of Spatial Attention

The distribution of spatial attention in visual field is one of the fundamantal topics in cognitive research. However, different paradigms lead to different and even conflict results, probably because of the influence of many ambiguous factors. Some papers figuered out the importance of the retinal eccentricity in some spatial attention studies. Whereas, still there were some researches which studied on spatial attention ignoring the potential influence of the retinal eccentricity. This research applied Scharlau's paradigm to investigate whether and how retinal eccentricity influences the gradient distribution of visual spatial attention.In Experiment 1, the participants were presented of two target stimuli with different SOAs, and were asked to make simultaneous judgment (SJ) unspeedly. There were two distance levels, long distance level and short distance level, which represents the distance between the two target stimuli,6.4°for the long distance level and 3.2°for the short, respectively. The authors also set two conditions. In the overlapped condition, the fixation point was overlapped with attentional point. Meanwhile, in the apart condition, the attentional point was covertly pulled away from the fixation point by a peripheral exogenous cue. To avoid the occurrence of response bias, the cue was designed to be backward masked by the following target. The authors compared the point of subjective simultaneous (PSS) in each condition and each distance level. Only the PSS of the far distance level in the apart condition was significantly different with 0 ms.In order to prevent the apparent movement which might influence the result of Experiment 1, the two target stimuli were designated with differernt topological structures in the following experiments. Experiment 2 was designed to test the hypothesis that there was no significant difference of the subjective brightness between the two stimuli. Taking the result of Experiment 2 under consideration, Experiment 3 was conducted by replicating the exact procedure of Experiment 1, except the following modifications:the two target stimuli were topologically different; the contrast degree was reduced; four dots converged to the center cross before each trial to ensure the subjects focused their attentions on the center cross. The result showed that a distance effect was found only in the overlapped condition but not in the apart condition. The results indicated that the gradient distribution of visual spatial attention was affected by retinal eccentricity.To conclude, the serial experiments indicated that retinal eccentricity influences the gradient distribution. Moreover, convergent data provided more evidences to support the "two attentional gradients theory" which claims there is an inhibition gradient centred at the fixation point and an excitation gradient centred at the cued location in the visual field. Then authors discussed the factors that may influence the attentional gradient researches, and drew a picture of further researches.