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SH L Chien; Lightness Constancy in 4-month-Old Infants Tested With Forced-Choice Novelty Preference Technique . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3997.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Chien at al. (ARVO 2001) reported that infants as young as 4 months exhibit adult-like simultaneous lightness contrast. Infants' lightness perception approximately follows Wallach’s ratio rule, indicating that the ability to extract information about luminance ratios is present early in infancy. Our present goal is to test whether infants of the same age exhibit lightness constancy when the background has the highest reflectance in the display. Methods: The forced-choice novelty preference (FNP) technique (Chien et al, ARVO 2001) was used to measure infants’ novelty responses. The apparatus was a 24»*30»*24» (L*H*D) testing chamber made of non-glossy white foam board, with a front 12»*12» open window for infants to view the stimuli. The stimuli were real paper surfaces of different reflectance (64% (light grey) and 23.5% (dark grey)) and were patterned as square smiley faces, presented against a homogeneous high reflectance background (90%, perceived as white). Two incandescent illuminations differing by about a factor of 3 were used. In the familiarization phase of each FNP trial, infants were exposed with two identical smiley faces under one illuminant for 3-5 seconds. In the test phase, the illuminant was either increased or decreased by about a factor of 3. The infant was presented one smiley face that maintained the same reflectance but with a novel luminance value (reflectance-matched face) and another smiley face of a novel reflectance but that maintained the same luminance value (luminance-matched face). The observer was blind to the location of the stimuli, and her task was to make a forced-choice judgment of which of the faces the infants prefer in the test phase. If infants have lightness constancy, they should prefer the face with the novel reflectance regardless of changes in illumination. Appropriate controls with constant illumination between the two phases were also included. Results: Infants (total n=20) looked significantly more at the face with the novel reflectance, regardless of whether the illumination was increased, decreased, or remained constant between the familiarization and the test phases. Conclusion: In all conditions, infants showed significant novelty preferences to a change in surface reflectance. Namely, the reflectance-matched face (with a novel luminance value) was seen as familiar across changes in illumination. This behavior indicates the presence of lightness constancy in 4-month-olds. Further investigations on the role of background reflectance are in progress.
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