Infant Color Vision: Moving Tritan Stimuli do not Elicit Directionally Appropriate Eye Movements in 2- and 4-month-olds

AbstractThe purpose of the present study was to investigate the capacity of infants to code the direction of motion of moving tritan-modulated gratings. Infant and adult subjects were tested with 0.2 c/d sinusoidal gratings moving at a speed of 20 deg/sec. Three conditions were tested: luminance-modulated gratings, tritan-modulated gratings, and luminance- vs tritan-modulated gratings superimposed and moving in opposite directions in a chromatic motion nulling paradigm. Two-month-old infants were tested in all three conditions, while 4-month-olds were tested in only the first two conditions. For infant subjects, an adult observer reported the direction of the slow phase of the infant's eye movements; adult subjects judged the perceived direction of motion of the stimuli. Luminance-modulated gratings produced directionally appropriate eye movements (DEM) in all age groups. Tritan gratings presented alone did not produce DEM in either 2- or 4-month-olds, but did so in adults. Mean equivalent luminance contrasts were near zero in 2-month-olds, and small but reliably above zero in adults. In sum, the present study provides no evidence that infants can code the direction of motion of moving tritan gratings. © 1997 Elsevier Science Ltd. All rights reserved

Achromatic contrast effects in infants: Adults and 4-month-old infants show similar deviations from Wallach’s ratio rule

AbstractWhen adults view a disk of light embedded in a higher luminance surround, the perceived lightness of the disk is largely determined by the surround to disk luminance ratio (Wallach’s ratio rule). In the present study, both adult and infant subjects were tested with multiple discrete trial procedures in which the surround luminance was decreased between the study and test phases of each trial. Tested with sequential lightness matching, adult subjects showed an approximate ratio rule, with a small but consistent deviation in the direction of a luminance match. Tested with a forced-choice novelty preference technique in combination with a cross-familiarization paradigm, 4-month-old infants showed preference minima that fell closer to the mean adult match than to the ratio rule. This finding suggests that, at least for a relatively simple visual display, 4-month-old infants’ looking preferences are governed by an adult-like achromatic contrast system

Infants code the direction of chromatic quadrature motion

AbstractThe present experiment uses a quadrature motion paradigm to investigate the motion correspondence cues used by young infants for coding the direction of motion of red/green isoluminant gratings. Three-month-old infants and adults were tested with 0.25 c/d luminance-modulated or red/green isoluminant gratings, either moving continuously or shifted in spatial quadrature. Both direction-of-motion and detection thresholds were measured, and motion:detection (M:D) threshold ratios were examined. Infants, like adults, could code the direction of motion of red/green quadrature-shifted gratings. In adults, M:D ratios were similar for continuous and quadrature motion. In infants, M:D ratios were higher for quadrature than for continuous motion, but elevations of similar magnitude were seen for both luminance-modulated and red/green gratings. The results suggest that frequency-doubled signals, such as those often seen in the magnocellular (M-cell) pathway, are not necessary for coding the direction of motion of isoluminant gratings in infant subjects. Two other theoretical options—mediation by the scatter of isoluminance points in the M-cell population, and parvocellular (P-cell) mediation—are discussed

Centering biases in heterochromatic brightness matching

AbstractWhen the method of constant stimuli is used to measure heterochromatic brightness matches, the resulting matches can be strongly biased toward the center of the range of test luminances used [Teller, D. Y., Pereverzeva, M., & Civan, A. L. (2003). Adult brightness vs. luminance as models of infant photometry: variability, biasability, and spectral characteristics for two age groups favor the luminance model. Journal of Vision, 3, 333–346]. In the present paper, we investigate the source of this centering bias. The stimuli were 2° red squares presented in a gray surround. In the main experiments, two ranges of stimulus luminance were presented in separate physical locations on a video monitor, but with test trials interleaved in time. Subjects either fixated a fixation cross (fixation condition), creating different retinotopic locations for the two luminance ranges, or foveated each stimulus as it appeared (foveation condition), creating identical retinotopic locations for both ranges. In the fixation condition, the two different stimulus sets resulted in a simultaneous centering bias—two different brightness matches at two different retinotopic locations at the same time. This effect was essentially eliminated in the foveation condition. A dichoptic foveation condition also revealed no centering bias. The results suggest that under the conditions tested, the centering bias is caused by a process located at a post-retinal but still retinotopically organized level of the visual system, rather than by either a retinal process or a more central, spatiotopically organized one