Abstract
Visual crowding is often framed in terms of the close spacing of letters within words, but relatively little research has examined whether the nature of reading influences the crowding of letter stimuli. In the present study, we examined crowding in the context of key attributes of reading: massive familiarity with upright letters, parafoveal processing of horizontally oriented letter strings, and left-to-right reading of languages such as English. We predicted that letters would show less crowding than other stimuli, that crowding would scale with eccentricity more for letters, that crowding would be weaker in the right visual field particularly for letters, and that these effects would be present primarily for horizontally flanked targets than for vertically flanked targets. Across 4 experiments, critical spacing was measured for letters, inverted letters, and Gabor patches at 6 locations across the horizontal meridian, with either horizontal or vertical flankers. In all versions of the experiment, letters had the smallest critical spacing, followed by inverted letters and Gabors. For horizontally flanked targets, critical spacing—expressed as a proportion of the eccentricity—was reduced in the right visual field and at smaller eccentricities. The increased eccentricity scaling was larger for letters compared to other stimuli. For vertically flanked targets, there were no hemifield effects, and the eccentricity effects did not interact with stimulus type. These results suggest an overall bias in the visual system to overlearned stimuli (e.g. letters) which allows it to better resolve crowding. The finding that—specifically for horizontal arrays—crowding is reduced in the right visual field and at near eccentricities may be related to observer’s lifetime experience reading horizontally flanked letter arrays in this part of the visual field. Hence, these results are an example of how relatively early visual processing may be altered by the long-term experiences of the visual system.