Children's conception of object, as revealed by their categorizations.

Six- to 11-year-old children were asked to sort objects in a construction set, to examine what types of objects they group together when performing a classification task. Half of the objects were simple pieces, and the other half were constructions made from those pieces. The results showed that these two types of objects are not clearly differentiated by children until relatively late: age 8 years in the first experiment and age 10 or 11 in the second. Children based their sorting on either perceptual or functional equivalency relations (logical sorting) or on suitability relations between objects of different levels (schemas).

Adjectives or nouns to refer to objects: effects on the complementation and inclusion performance of 6- to 9-year-old children.

Due to the exclusivity bias (a given object is considered to have only one generic name), inclusion problem solving by children should be adversely affected by the use of nouns rather than adjectives to refer to objects. In contrast, the children's complementation behavior should be facilitated, because naming promotes the organization of objects into additive subclasses under a generic class. Groups of children 6 to 9 years old were asked to solve complementation and inclusion problems about a set of objects designated by nouns or by real or nonsensical adjectives. The results showed that complementation performance was indeed enhanced by the use of nouns, but inclusion behavior was not affected by the type of term used.

Referential set presentation effects on complementation by 6-year-olds.

What difficulties do children encounter when responding to complementation instructions? The responses of 50 children to six complementation requests were examined. For half of the children, the objects in the referential set were pooled, and for the other half, they were physically separated by category (pencils were presented in a pencil box, buttons in a sewing kit, and balls of yarn in a knitting basket). Reinforcing the identifying status of the semantic property by separating the objects into categories led to an increase in the number of responses bearing on the subset designated in the instructions (e.g., in response to "Give me everything that is not a black button," the children handed over only the nonblack buttons). In contrast, older children gave responses based on the entire set. The meaning attributed by children to object properties and the effects of that attribution on processing mode merit further study.

The influence of experimenter attitude on the performance of children of different cognitive ability levels.

We investigated the influence of the experimenter's attitude on children's performance in a classification task. We chose 96 children (M age: 5 years, 9 months) on the basis of their performance in a spontaneous classification task. Forty-eight children made partial alignments on the basis of a link established from one object to the next (O-level group); 48 looked for objects having one common property (P-level group). The children had to perform a dichotomy task in two testing situations: one with a caring experimenter, and one with an indifferent experimenter. In the O-level group, the children's performance was superior when the experimenter was caring even though they did not seem to notice the difference between the two attitudes. P-level children clearly distinguished the experimenter attitudes, but their performance remained the same. To determine children's actual abilities accurately, researchers must take into account children's interactions with both objects and partners.