Objective: This study investigated the effects of familiarity on the performance of routine (familiar) naturalistic actions (NAs) that had been performed several times prior to the experiment (e.g., making coffee) and novel (unfamiliar) naturalistic actions (NNAs) that had not been performed prior to instruction (e.g., making a mock volcano). We hypothesized that similar psychological processes were associated with both types of action, but that memory and executive functions would be more important for NNAs. Method: In Experiment 1, 18 undergraduates verbally described NAs and NNAs as they observed the tasks being performed. In Experiment 2, stroke patients, impaired (n = 4) or unimpaired (n = 4) on a test of general cognitive function, and 12 controls, physically enacted and arranged in correct order photos of NAs and NNAs. Results: In Experiment 1, the central (crux), but not the noncentral (noncrux) actions, associated with NAs and NNAs were verbally described. In Experiment 2, NA and NNA enactment and photo arrangement performance was lower in the impaired group compared with controls. The impaired group had higher omission (omitting an action) than commission (performing an action incorrectly) crux action error rates for NAs, but the reverse pattern for NNAs. NA performance was more strongly associated with general cognitive function, whereas NNA performance correlated more strongly with executive functioning and memory measures. Conclusion: Both types of task involve overlapping cognitive processes. Memory and executive function may be more important for NNAs because these tasks are encoded into memory at study.
