The human cognition system is like a computer. Two main limitations are the amount of information that it can possess at one time and the speed with which is processes this information. Second, assumption that there are mechanisms or processes of change that underlie the processing of information. Assumes that cognitive development is a self- modifying process; that the child uses strategies she has acquired from earlier problem solutions to modify her responses to a new problem. Assumption that careful task analysis is crucial; that the task itself influences the child"s own level of development. Analysis on this is called microgenetic analysis: a very detailed examination of how a child solves a problem. Describes how information enters and flows through the mind as it is processed. Many steps; helpful diagram on page 342 fig. Then goes to sensory register: info is stored in original form but very briefly; 1 second, doesn"t change over development.