Teaching young children to use contact lenses.

Young children with surgically removed lenses and extreme nearsightedness can benefit from contact lenses, but their parents may need instruction to teach their children to accept lenses. In this study, 4 children under the age of 5 years were taught contact lens wear using a shaping procedure. Compliance was rewarded with praise and tangibles, and noncompliance was followed with brief time-out for 3 of the children and restraint for the 4th. Three children showed high compliance during an initial shaping procedure, with a decrease in compliance during initial insertion of the lenses. At 3- to 10-month follow-up, levels of compliance were high. Insertion and removal of lenses were accomplished in substantially less time, with little crying and no need for time-out. All 3 children continue to use the lenses daily, and 2 have shown improved visual acuity. The 4th child, who has Down syndrome, showed low levels of compliance with need for physical restraint throughout. Although his parents reported high compliance when he first went home, fitting difficulties and an infection resulted in plummeting of compliance, and contact lens use was discontinued. This procedure has been used successfully at the same hospital with 11 of 13 other children between the ages of 14 months and 7 years 4 months. Implications for selection of suitable candidates for this intervention and ways to decrease costs are discussed.

Matching performance and the similarity structure of the stimulus set.

To compare two general approaches toward understanding how objects are classified, this article explores performance in a series of studies that required matching visually presented letters. One general approach has stressed the analysis of details or elements of the input pattern. The other approach has focused on the relationships between the various elements and objects that the observer might expect to occur in the task. In empirical support of the first approach, many researchers have observed that the time it takes a subject to report that two visually presented letters have the same name is less when these letters are physically identical (e.g., A-A) than when they are physically different (e.g., A-a). This relative ease of matching physically identical letters has been attributed to a visual process that matches the letters on the basis of their physical characteristics. In support of the second approach, the studies in this article replicate this finding, but only for data averaged across letter parts. The data from individual letter pairs do not reflect this temporal hierarchy. Individual letter performance for an entire set of letters has not previously been reported, and the importance of analyzing fine structure in data is stressed. It is shown that physical identity matches can be reliably faster or slower than name identity matches. The similarity structure of the total stimulus set reliably predicts which result will occur. Within the limits of the variables studied, this conclusion is shown to be independent of the criterion for the type of match the subject is asked to make (physical identity or name identity) and of the temporal and physical separation of the letters. The readiness with which the presented stimuli can be discriminated from other members of the stimulus set controls performance. For example, as Experiment 1 shows, it is easy or difficult to report o-o as "same" depending on what other letters are used in the task. Lockhead's holistic-discriminability model provides a framework for interpreting these demonstrations that matching performance does not depend only on the stimuli physically present. Performance depends on the similarity or discriminability between the presented stimuli and other stimuli the observers know might be presented.

Putting properties of objects in context: reply to Nickerson.

Nickerson argued that "the properties of both the immediate stimulus and the set of possibilities are important determinants of performance," as if these are separate and independent things. However, there cannot be relations that are separate from the properties that compose them. My studies demonstrate that similarity relations are important to performance. The question here is whether properties of the presented stimulus, independent of these relations, are also important to performance. There currently seems to be no evidence that they are.