A non-verbal process dissociation procedure to disentangle explicit from implicit sequence learning

Human adults can extract regularities through implicit learning, resulting in non-conscious knowledge, or through explicit learning, leading to conscious and reportable knowledge. Experiments aiming to disentangle implicit from explicit learning are limited by their heavy reliance on verbal instructions. This prevents the creation of a fully implicit situation and restricts the populations studied, effectively excluding non-verbal individuals. To address these limitations, the current study validates a non-verbal version of a standard test to assess implicit and explicit sequence knowledge: the Process Dissociation Procedure (PDP). In the PDP, after a learning phase where participants are exposed to spatial regularities, their control over sequence reproduction-a hallmark of explicit learning-is probed by contrasting two conditions: an inclusion condition, where participants must reproduce the sequences they have learned, and an exclusion condition, where they must avoid reproducing these. Departing from conventional design, inclusion/exclusion instructions were removed, and participants had to discover the task rules through trial and error. At the end of the experiment, they were asked to describe their understanding of the task. Data from 32 human adults showed that ceiling-level performance in inclusion and exclusion conditions occurred only in the subgroup of participants who verbally reported both the PDP rules and the presence of sequences. In contrast, others performed around the chance level. These results confirm that awareness is necessary for controlling sequence reproduction. This first non-verbal adaptation of the PDP provides a promising method to disentangle explicit from implicit learning in children and non-human animals.