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Deyue Yu; Effect of spatial complexity on resolution, mislocations and crowding. Journal of Vision 2015;15(12):99. doi: 10.1167/15.12.99.
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© ARVO (1962-2015); The Authors (2016-present)
Reading is limited by three sensory factors: resolution (letter acuity), mislocations (uncertainty about spatial arrangement of letters), and crowding (the deleterious interference of nearby letters on target identification). Previous studies found a negative impact of flanker complexity on letter identification. Here we investigated whether the modulatory effect of complexity is restricted to crowding. Eight subjects identified single letters or the middle letters of trigrams presented at 10° to the left or right of the fixation point. Flankers were always duplicate letters, either identical or different from the middle target letter. Averaged across subjects, identification accuracy was 98.6% for the single-letter condition, 83.4% for the identical target-flanker condition, and 57.4% for the nonidentical condition. Multiple linear regressions were performed to assess the effect of letter complexity. In single-letter identification, higher complexity was associated with more errors. In the nonidentical condition, flanker and target complexities played opposite roles on performance with stronger influence from flankers. Higher flanker complexity led to more errors while higher-complexity targets made identification easier. Given the stronger effect of flanker complexity, we expected and indeed found that for the identical target-flanker condition the average effect of complexity (across target and flankers) on performance was negative (i.e. poorer performance for higher complexity). For the nonidentical condition, we teased out mislocation and crowding errors and found that mislocations depended on target complexity (r< 0) whereas crowding errors correlated with flanker complexity (r>0). Our findings demonstrate a general impact of letter complexity on reading-related sensory constraints. The effect of flanker complexity on crowding is consistent with the view that crowding may be due to compulsory averaging of target and flanker features or flanker substitution. However, substantial crowding under the identical condition indicates that change in target appearance in this case may be attributed to a process other than assimilation and substitution.
Meeting abstract presented at VSS 2015
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