The Development of Cognitive Flexibility in Childhood

The experiments presented in this thesis explored the processes that contribute to cognitive flexibility between the ages of three and eleven years. A new paradigm, the Switching, Inhibition and Flexibility Task (SwIFT) has been used to test whether the paradigms that we use to study cognitive flexibility can lead to incidental, or unexpected performance costs. The roles of core executive demands and incidental task demands on preschool children’s cognitive flexibility performance were explored in the first section of this thesis. Perseveration, which is the most common pattern of failure for preschool children, was strongly associated with incidental demands of the most commonly used measure, and not associated with the core demands of switching between dimension- level rules. Further experiments went on to determine that preschool children’s performance in both cognitive flexibility and working memory tasks can be affected by the medium through which those tasks are presented (computer-based or object-based); and that cognitive flexibility can be affected by the wording of the cues used to prompt task switches. The role of set size in school-age children’s cognitive flexibility was also explored in this thesis. In a series of experiments, it was shown that tasks with a small set size lead to greater switch costs than tasks with a large set size, and that this was due to bottom- up priming processes which facilitate task repetition and impair task switching. Furthermore, there was evidence to support a shift from stimulus-specific to abstract levels of priming during the early school years. This suggests that there are changes in the mechanisms through which set size may affect performance across development. Throughout this thesis, new measures were used to transfer research questions between the pre-school, school age and adult age groups. This research is thus an important progression towards understanding how cognitive flexibility develops through the entire developmental period.