Recent findings in cognitive development have shown that young children are slow to grasp certain fundamental characteristics of thinking - namely the incessant and often uncontrollable nature of this process. To extend these findings, three studies were conducted investigating 5- and 6-year-olds and 8- and 9-year-olds' ability to recognize disruptions in the stream-of-consciousness, specifically in the form of an intrusive thought about an emotionally-charged event. In Study 1, children's judgments about the emotional valence, desirability, and controllability of intrusions were probed. Results indicated that older children more readily identified intrusions as negatively charged and unwanted than did younger children, whereas both age groups judged thoughts as difficult to control. Study 2 investigated children's understanding that intrusions are unintended, as well as the idea that consciousness is limited such that people cannot think about two things at once. Results from Study 2 showed that older children were more aware of the unintended nature of intrusions, as well as limits on concentration. In addition, older children displayed a more comprehensive conception of intrusions. Study 3 investigated children's understanding of the impact of intrusions on concentration by asking whether children realize that the level of absorption in a given task affects the degree to which an intrusion is noticed or functions as a distracter. The definition of intrusion was extended to include perceptual intrusions ( e.g., noises) and somatic intrusions ( e.g., hunger pangs) as well as cognitive intrusions ( e.g., unwanted thoughts). Surprisingly, results from Study 3 indicated that both older and younger children were highly systematic in judging that the more absorbed protagonist would be less likely to notice or be distracted by an intrusion than the less absorbed protagonist.

In addition, both age groups were particularly aware of the way in which level of absorption affects the degree to which an intrusion functions as a distracter. Overall, results from these studies lend insight into children's developing understanding of intrusive thoughts and the impact of these thoughts on concentration. They also have implications in various clinical settings which require children to be sensitive to the presence and content of their thoughts and feelings.