Effect of attention on human direction-discrimination thresholds at iso-eccentric locations in the visual field: A registered report protocol.

Human visual perceptual performance is strongly dependent on a given stimulus' distance from the line of sight, i.e. its eccentricity. In addition, multiple studies have shown a dependence on a stimulus' angular position relative to the fovea. In humans, the resulting spatial profile of perceptual performance (the "performance field") typically shows better performance near the lower vertical meridian, compared to the upper vertical meridian, and better performance near the horizontal meridian compared to the vertical meridian. Predominantly, these variations have been interpreted as sensory inhomogeneities. But it has also been shown that they are modulated by the allocation of spatial attention, either homogeneously elevating performance or compensating for the sensory inhomogeneities. Here, we propose a study protocol for pre-registration to investigate such interactions between sensory and attentional effects. First, we will determine performance fields for time-dependent, dynamic stimuli, namely the direction discrimination of moving random dot patterns. Then, we will establish whether directing focal attention to a particular stimulus location differentially improves thresholds compared to a distributed attention condition.