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M. J. Dengler, M. Engles, K. Varga, J. Frick, B. R. Hammond, Jr.; Contrast Thresholds in Infants Compared to Adults. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1705.
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Much is known about the developing visual system. There are few studies, however, that use stimuli that generalizes outside of laboratory settings (e.g., using Rayleigh-matched sky light). This is important for comparing infant and adult abilities and determining the limits of the developing visual system.
9 infants (age range = 121-277 days) and 9 adults (age range = 20-27 yrs) were assessed. A three channel optical system generated the stimuli. Infants were tested using a two-alternative forced choice staircase method in combination with preferential looking to a mid wave (550nm) target located at the center of one of two short wave (460nm) surrounds (36 deg) to determine threshold for sensitivity. Similarly, adults were tested using a two-alternative forced choice staircase method using the same stimuli.
ANOVA was conducted to assess the relationship between age (infants vs. adults) and sensitivity level. Infants and adults did not differ in sensitivity to the stimulus F(1, 16) = 3.25, p= .09.
Although the visual system is the sensory system least developed at birth, by 9 months of age infants are capable of detecting contrasts between a mid-wave target and short-wave surround. Like many static visual thresholds, contrast detection between these monochromatic stimuli appears to develop early. This result is consistent with data showing that color vision abilities develop early and macular pigment tends to be at adult levels (with similar variability) also relatively early. With respect to the latter, macular pigment levels would be expected to influence the task since they absorb the surround more heavily than the target (hence, higher levels would tend to enhance contrast).
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