Theoretical and methodological analysis of partial knowledge

A theory of partial knowledge is proposed as an explanation of cognitive development, and methods are described for testing the theory. The theory consists of three structure-process pairs, each of which postulates a type of cognitive structure and a developmental process specific to that type. In restricted knowledge, a unitary algorithm is the cognitive structure, and amendment is the developmental process. In variable sampling, a structure of unitary substitutes is paired with a process of selection. In variable integration, modular components are paired with self-monitoring. Methods for testing the theory form a sequence of mathematical models. The first model in the sequence, called a model of double assessment, is described both verbally and mathematically. Other models in the sequence are described verbally with reference to other articles for the formal mathematics. Also described are some nonmathematical methods to be used as sequels to the double assessment model.     

The emergence of representation in search: Understanding the hider as an independent agent

Corrigan's results point the way toward a reconceptualization of how the development of representation affects search. The child does not cognitively recreate the invisible displacements of the object. Instead she seems to understand that the hider is an independent agent who can use simple hiding strategies that the child does not directly perceive. This representational skill for search, we propose, is one realization of a general representational capacity that emerges late in the second year. The general capacity is defined structurally as the ability to coordinate two sensorimotor systems into a single skill. Although there seem to be some discontinuities in the emergence of the representational capacity, its development is mostly gradual and continuous.     

Temporal order judgments with amnesia

The hypothesis that patients with anterograde amnesia fail to recognize the temporal relations among recognizable past events was evaluated. Experiment 1 showed that order recognition for words in a list was at chance levels even though event recognition was significantly above chance. The same pattern did not obtain for intact adults. Experiment 2 examined event and order recognition for news events. Amnesics' event recognition for news events was quite accurate and comparable to controls, yet their order recognition was significantly below that of controls, again at chance levels. It is argued that the failure to encode the temporal relations among events has broad consequences for memory performance in general.     

Hemispheric asymmetry in memory search for four-letter names and human faces

Two memory search experiments were conducted using vertically oriented four-letter names and human faces as stimuli. Subjects were required to indicate as quickly and as accurately as possible whether or not a single probe stimulus (presented for 150 msec to either the left or right visual field) was contained in a set of 2, 3, 4, or 5 items being held in short-term memory. The probe stimuli were presented alone (clear condition) or centrally embedded in a matrix of dots (degraded condition). In Experiment 1 (involving names), a right visual field/left hemisphere advantage was obtained and pinpointed at the encoding stage rather than at the memory comparison stage of the information-processing system. For Experiment 2 (involving human faces), no hemispheric advantage was readily observed. In each experiment, both the left hemisphere and the right hemisphere employed an abstract memory comparison operation from which the effects of probe degradation have been removed. These results are discussed in terms of their implications for various models of hemispheric asymmetry.     

A model of cognitive development across the life span

A model of cognitive development across the life span was proposed. A distinction was drawn between an individual's unexercised potential, which refers to the level of performance that would be expected if the individual had no exercise and/or training on the ability in question, and an individual's optimally-exercised potential, which refers to the level of performance that would be expected if the individual had optimal exercise and training. Both unexercised and optimally-exercised potential levels were proposed to increase with age up to early adulthood and decrease gradually thereafter. The region between the two types of potential, which was also suggested to increase during childhood and decrease during later adulthood, indicates the extent to which exercise and/or training can affect performance. This model was shown to be consistent with a number of different types of empirical findings.