ABSTRACT
Let me begin by distinguishing between two aspects of each and every cognitive task, whether it be a judgment of equality in a conservation task, the solving of the mathematics story problem, responding as a partner in a conversational dyad or interpreting a story. The first aspect is the by now familiar operational component of the task. Once the subject is shown the beakers or told about the price and number of apples, something must be done about them, some mental action undertaken. We know now that the nature and quality of these mental acts varies more or less systematically with age, with problem domain, with context or setting. Mental acts are the means whereby we come to know about the world; and so I will call them collectively the epistemic aspect of cognition.
