Task-dependent learning of non-adjacent dependencies: Success in a familiarity rating task but failure in a two-alternative forced-choice task.

Acquiring non-adjacent dependencies (NADs) from continuous sequences can be challenging for adults, with prior research showing varied outcomes depending on the properties of the stimuli and methods of assessments. This study investigated whether different behavioral tasks vary in their ability to detect NAD learning. All participants (N = 322) underwent equivalent training phases involving exposure to NAD trigrams in a continuous speech stream. During the test phase, their learning of the grammatical NAD patterns was evaluated using either a two-alternative forced-choice (2AFC, N = 200) task or a familiarity rating task (N = 122). Participants in the 2AFC task performed at chance, regardless of whether the ungrammatical trigram differed minimally or maximally from the grammatical trigram. In contrast, participants in the familiarity rating task rated grammatical trigrams as more familiar than ungrammatical ones, suggesting that the familiarity rating task may be more sensitive to subtle learning effects. These findings highlight the importance of task design in the detection of NAD learning, with implications for the broader field of statistical learning research.