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Biomedical subjects

C Ankrum

Publications and source records attributed to C Ankrum.

3 recordsLinked to original sources

Memory for objects and parts.

Performance on whole comparisons of two whole objects was compared to that for partial comparisons of a whole object and a part. In particular, same-different comparisons were measured for sequential displays of two-dimensional line figures. The comparisons were analogous to those in the word priority paradigm (Johnson, 1975). The whole comparisons were found to be more accurate and faster than the partial comparisons. This whole advantage was also found for accuracy using a two-alternative forced-choice procedure. This effect was found for brief displays of a single object and for longer duration displays of two objects. It was also found for three different sets of line figures. In contrast, the whole advantage was not found for unconnected figures. These findings were interpreted in the context of hierarchical representations of objects and parts.

Adult

Spectral sensitivity and chromatic discriminations in 3- and 7-week-old human infants.

The chromatic discrimination capabilities of 3- and 7-week-old infants were tested using 8 degrees, 417-, 448-, 486-, 540-, and 645-nm test fields embedded in a 547-nm surround and 486-nm test fields in a broadband red surround. In corroboration of earlier studies, few 3-week-old infants demonstrated chromatic discriminations, although their performance was somewhat better when one of the lights was long wavelength. Most 7-week-old infants could make chromatic discriminations, but they still demonstrated performance minima. The radiances of the test lights at the infants' performance minima were used to generate a spectral luminous efficiency curve. This curve agreed with both the adult heterochromatic brightness matches measured at 30 degrees of visual eccentricity in situ and the standard adult scotopic sensitivity curve V(lambda) over the short- and mid-wavelength range but deviated from both adult curves for the 645-nm test stimulus on a 547-nm surround. The results suggest that rod-initiated signals play a major role in infants' visual performance under the conditions tested.

Aging

Monocular and binocular acuity estimation in 18- to 36-month-olds: acuity card results.

The acuity card procedure is a useful method for measuring visual acuity in infants 1 to 12 months of age. The results of the present study indicate that the procedure is also a viable method for estimating acuity in children 18 to 36 months of age. Monocular and binocular estimates of acuity were obtained with the acuity card procedure on 36 normal children, 9 each at ages 18, 24, 30, and 36 months. At each of the ages, means and SD's of acuity estimates agreed well with acuity norms from established operant procedures. Mean durations for monocular and binocular estimates averaged 2 to 4 min, and nearly 100% of children were tested successfully both monocularly and binocularly. The flexibility of the required response and the short test times make the acuity cards a promising test of visual acuity in this typically difficult-to-test age range.

Child Development