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Author(s): Clark, Cynthia L; Hardy, Joseph L; Volbrecht, Vicki J; Werner, John S | Abstract: BackgroundOur lab has previously demonstrated losses in contrast sensitivity to low spatial frequencies under scotopic conditions with older adults. It is not clear, however, whether the temporal frequency of a stimulus alters the relation between age and the spatial contrast sensitivity function (sCSF) under scotopic conditions.MethodsA maximum-likelihood, two-alternative, temporal forced-choice QUEST procedure was used to measure threshold to spatially and temporally modulated stimuli in both young (mean = 26 years) and old (mean = 75 years) adults.ResultsIn general, the shapes of the spatial and temporal CSFs were low-pass for both young and old observers; contrast sensitivity decreased at approximately the same rate with increasing spatial frequency and temporal frequency for both age groups, although the overall sensitivity of the old group was lower than that of the young group. The high-frequency resolution limit was lower for the old group compared to the young group.ConclusionsThe differences in contrast sensitivity between the young and old groups suggest a uniform loss in sensitivity of the channels mediating spatial and temporal vision. Because of this loss, the spatial and temporal window of visibility for the older adults is compromised relative to the younger adults.

Threshold vs. intensity (tvi) functions were measured under conditions in which the slope of the rising branch approximated the deVries–Rose law in order to evaluate the contribution of intrinsic visual noise (dark light, Eigengrau) to age-related elevations in threshold under photopic conditions. Data were obtained from 48 observers (20–88 years) using a temporal 2AFC procedure. The stimulus was centered at 8° nasal retinal eccentricity and consisted of a 560 nm, 14.4′ test flash (10 ms) concentric with a steady 500 nm (12.9°) adapting field (13 intensity levels ranging from 0–9 log quanta · sec−1 · deg−2), which resulted in clear scotopic and photopic branches. Photopic thresholds increased linearly with age at a rate of 0.08 log unit per decade at the cornea. The mean slope of the rising portion of the tvi functions (in log–log coordinates) was 0.62, and not correlated with age. Dark light values increased with age, but not significantly. Dark light was a statistically significant predictor of individual differences in absolute photopic threshold, but it is not responsible for age-related increases in threshold under photopic conditions. © 2000 John Wiley & Sons, Inc. Col Res Appl, 26, S48–S52, 2001

Previous studies of infant attention, learning, and memory have revealed that certain stimulus properties may increase an infant's arousal or excitation level, thereby increasing responsiveness and facilitating the encoding and processing of information. In a series of experiments aimed at identifying stimulus determinants of sensitization, we examined visual responses from 4-month-old infants to spectral lights. Habituation data were obtained from 92 full-term infants separated into one of five groups. Each group viewed either a broadband white light (correlated color temperature approximately 2800 K) or one of four different spectral lights (lambda d = 470, 510, 570, or 650 nm) approximately corresponding to the elemental hues blue, green, yellow and red, respectively, for adults with normal trichromatic vision. Stimuli were equated in luminous efficiency for a standard infant observer. Stimulus fixation was recorded for twelve 10-s presentations, each separated by 10-s interstimulus intervals (ISIs). The results show that mean fixation times to the red and green lights were significantly greater than those for the blue and white light. Mean fixation time for the yellow light was also reduced (significantly) compared to the red but not the green light. These results suggest that the chromatic properties of red and green spectral lights may be more sensitizing to infants than those of the blue, yellow, or white lights.

Chromatic and achromatic components of 15 broadband surfaces were scaled by 15 younger (mean age = 21.3 yrs) and 15 older (mean age = 71.9 yrs) subjects. Colored surfaces were obtained from the OSA Uniform Color Scales and presented as 2°-diameter test stimuli that were freely viewed. Stimuli were presented in a grey (L = 0) ganzfeld-like hemisphere with an illuminant having a correlated color temperature of 6200 K. Five stimuli were presented at three lightness levels (L = −4, 0 and +4). Each lightness level included samples chosen so that one pair plotted approximately along a tritan axis in MacLeod-Boynton receptor-excitation space and another pair plotted on an axis of constant S-cone stimulation. The appearance of each test stimulus was scaled using the hue terms red, green, yellow and blue, and in terms of the proportion of overall chromatic content. The results indicate that hue names were used similarly for the two groups of subjects, however, older subjects perceived all stimuli as having less chromatic content than demonstrated by younger observers. Differences between the two age groups in perceived chromatic content of the test stimuli progressively increased as the lightness and luminance levels of the test stimuli decreased. Results obtained from control experiments suggest that this difference between the two age groups is not due to the influence of senile miosis or lenticular senescence leading to variations in the illuminances and spectral compositions of the test lights reaching the retina. © 1993 John Wiley & Sons, Inc.

Chromatic induction was measured in terms of the wavelength of a central 1°, unique yellow field surrounded by annuli that varied in wavelength, area, contrast, and overall retinal illuminance. In the first experiment, a 1.3° surround was varied from approximately 470 to 670 nm, using an overall illuminance range from 0.5 to 4.0 log trolands. The illuminance contrast between the center and surround was 1.0 (i.e., isoluminant). The results indicated that the wavelength of unique yellow shifted in the direction of the wavelength of the surround at all intensities. The magnitude of the shift, however, decreased with increasing intensity for middle- and long-wavelength surrounds. The latter result was not expected from previous research. Experiment 2 tested the hypothesis that this might be due to a Bezold-Brucke effect in which the hue of the surround changes with increasing retinal illuminance. The relative influence of Bezold-Brucke hue shifts on chromatic induction was manipulated by changing surround area and luminance contrast. Results of this experiment were consistent with the hypothesis that changes in color appearance with increases in intensity may influence the magnitude of chromatic induction.

SCHUBERTH, RICHARD E.; WERNER, JOHN S.; and LIPSITT, LEWIS P. The Stage IV Error in Piaget's Theory of Object Concept Development: A Reconsideration of the Spatial Localization Hypothesis. CHILD DEVELOPMENT, 1978, 49, 744-748. Stage IV in the development of the object concept has been defined by Piaget in terms of the infant's perseverative search for an object at a place where it has previously been recovered. The infant's failure to search for the object in a new hiding place is believed to reflect a concept of object that is not yet differentiated from a concept of place. An alternative hypothesis is that stage IV errors reflect difficulties in spatial localization; that is, the infant's limited understanding of space permits conceptions of place only in terms of prior actions. To evaluate the two explanations, 12 9-month-old infants watched as a toy was hidden at location A and then were allowed to retrieve the toy. Then they were allowed to search for a new toy hidden at location B. A group of 12 control infants searched for the same toy, first when it was hidden at A, and then at B. Results showed that the controls were more likely to err on their first B trial and that they generated longer perseverative error strings than the toy-change infants. This finding is consistent with Piaget's theory that the stage IV infant's concept of object is not yet differentiated from the concept of place.

Adaptive hue shifts of the achromatic point were measured in conditions in which a test field was presented as a flashed increment on steady chromatic backgrounds. The variables investigated were background chromaticity, luminance, and stimulus contrast. The results could be accounted for quantitatively by a mechanistic model with the following properties: discounting of the (steady) background, or ac-coupled signal processing; cone spectral sensitivities as estimated by Vos and Walraven; and receptor-specific gain controls that have the same action spectra and gain characteristics as Stiles' π5, π4, and (modified) π1 mechanisms.