Psychologists found that adolescents struggled when they had to hold a conversation at the same time as carrying out a cognitive task such as remembering a string of numbers.

This may affect performance on virtually any cognitive task.

In each case subjects would repeat a word or number for several seconds, then perform the cognitive task using that word.

In regard to extrinsic stress, the study focused on stress that was not related to cognitive task but was elicited by other situations.

Furthermore, the distinction between the categories can be seen as artificial since any given cognitive task may entail a number of processes.