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This is a follow-up on “Peripheral visual detail”. Here, we continue to investigate whether saccades improve peripheral visual perception. Participants will perform again a peripheral visual discrimination task on object stimuli before and after an inspection phase. In this version of the experiment, however, the tasks between peripheral phases and the inspection phase are switched. In the peripheral phases, participants categorise objects as electronic or non-electronic and in the inspection phase they perform the tilt discrimination task. The idea is that object categorisation benefits more from inspecting, i.e. learning something about, the object and therefore this new setup is expected to lead to larger difference between inspection conditions than the previous setup of “peripheral visual detail”. In addition, here we have one more inspection condition in which the object is presented only peripherally. We expect the same pattern of results which we expected in the previous version of the experiment and in the additional peripheral-only inspection condition we expect the least (compared to the other inspection conditions) improvement in discrimination performance from peripheral phase I to peripheral phase II. This peripheral condition serves as further control in contrast to the foveal condition to find out whether inspecting the object has some influence at all on peripheral object perception.

The visual field of human beings is very accurate and detailed only at the centre. Towards the periphery visual detail decreases rapidly. Despite this limitation of the eye, we usually have the subjective impression that visual detail is present in a much larger area of the visual field. It has been hypothesised that the cause of this impression is tightly linked to saccadic eye movements. We make saccadic eye movements about three times a second. Every saccade provides the opportunity to learn how peripheral visual input, which is less detailed, turns into foveal input, which is more detailed. It has been hypothesised that this association process allows us to predict and perceive visual detail in a larger area of the visual field than what the anatomy of the eye allows. This hypothesis has received some empirical support, however, it has not yet been test directly. We will investigate whether saccades do in fact improve peripheral visual perception. Participants will perform a peripheral visual discrimination task on object stimuli before and after an inspection phase. During the inspection phase objects will be inspected (1) with a saccade, (2) control condition without a saccade imitating the visual input provided by a saccade with a peripheral preview and a foveal view of the object while constantly maintaining fixation, (3) central-only presentation, a foveal baseline condition without saccades and without peripheral preview. If saccades increase visual detail in the periphery, we expect that discrimination performance will increase from pre-inspection to post-inspection for objects inspected with a saccade (condition 1). For objects of the no-saccade control condition (2), discrimination performance might still improve but not as much as in the saccade condition. In the baseline condition (3) we expect the same increase as in the no-saccade control condition or no increase at all. This third baseline condition will tell us whether peripheral detail can also be increased by associating peripheral and foveal views of an object even in the absence of saccades. Alternatively, it is possible that we do not find this pattern of results which would indicate that saccades to not increase the detail in peripheral vision and that peripheral detail is an illusion or that our experimental protocol was simply not suitable to test this hypothesis.

The world appears stable despite saccadic eye-movements. One possible explanation for this phenomenon is that the visual system predicts upcoming input across saccadic eye-movements, based on peripheral preview of the saccadic target. We tested this idea using concurrent electroencephalography (EEG) and eye-tracking. Participants made cued saccades to peripheral upright or inverted face stimuli that could change (invalid preview) or keep their orientation (valid preview) across the saccade. Experiment 1 demonstrated better discrimination performance and a reduced fixation-locked N170 (fN170) with valid than with invalid preview demonstrating integration of pre- and post-saccadic information. Moreover, the early fixation-locked EEG showed a preview face inversion effect suggesting that we perceive pre-saccadic input up to about 170 ms post fixation-onset, at least for face orientation. Experiment 2 replicated Experiment 1 and manipulated the proportion of valid and invalid trials (mostly valid versus mostly invalid, 66.6% to 33.3%) to test whether the preview effect reflected active expectations. A whole-scalp Bayes factor analysis provided evidence for no influence of proportion on the fN170 preview effect. Instead, before the saccade the preview face orientation effect declined earlier in the mostly invalid than in the mostly valid block suggesting some form of pre-saccadic expectations. We conclude that visual stability is achieved by two trans-saccadic integration processes: pre-saccadic prediction, reflected in the pre-saccadic proportion modulation, and early post-saccadic change-detection reflected in the fN170 preview effect.