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Rishi Kothari, Kate Mahon, Marisa Carrasco; Characterizing visual performance fields in children. Journal of Vision 2005;5(8):186. doi: 10.1167/5.8.186.
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INTRODUCTION. For adults, we know that contrast sensitivity and spatial resolution are better along the horizontal than vertical meridian-a.k.a. horizontal vertical anisotropy (HVA)-and better in the lower than upper vertical meridian-a.k.a. vertical meridian asymmetry (VMA). Speed of information accrual in adults follows this same pattern, i.e. it is faster along the horizontal meridian and slowest at the upper locations (Carrasco et al., 2001, 2004). To assess whether ecological factors modulate these performance fields, we investigated whether the discriminability asymmetries are present with grammar school children.
METHODS. Observers performed a 2AFC orientation discrimination task on Gabor patches tilted +/− 30° from vertical. Each trial consisted of a central fixation point (.2°), which was soon replaced by a smiley face (1°) to maintain participants' fixation and to signal the onset of the trial. A 2° Gabor (4-cpd) was presented for 100 ms at one of 8 equally probable iso-eccentric (6°) locations. The brief display duration precluded eye movements, allowing us to equate field and retinal eccentricities.
RESULTS. The HVA was present for all adult and child observers. Surprisingly, the children exhibited an inverse VMA to that of adults; whereas adults' performance was superior at the lower regions of the vertical meridian, children's performance was better at the upper regions. This finding suggests that ecological factors may help modulate the visual constraints underlying the VMA. Studying the developmental course of visual field asymmetries helps elucidate the role that the environment plays in perceptual performance, and may have implications for human factors.
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