Validity of the think-aloud procedure in comparison to other methods for studying the phenomenological features and memory of spontaneous thought

A hallmark of the human mind is its tendency to generate spontaneous thoughts, whether during tasks or in idle moments. This phenomenon is typically studied in the laboratory using the Thought-Probe Protocol (TPP), in which participants report the content of their thoughts when prompted at various intervals. Although well validated, the TPP nonetheless suffers from several limitations, such as its inability to track the flow of thoughts between probes. To address these issues, researchers have recently revisited the Think-Aloud Protocol (TAP), which involves the continuous verbalization of spontaneous thoughts. While the TAP offers access to the ongoing flow of thoughts, its validity relative to other methods has not yet been fully established. In this study, we compared four methods for assessing spontaneous thoughts: the TAP, TPP, Daily Life Experience Sampling Protocol (DLESP), and retrospective thought listing. We focused on the phenomenological characteristics of thoughts and features that predicted their recall after a one-day delay. Our results revealed minimal differences between the TAP and TPP in terms of thought characteristics and memory predictors. However, thoughts reported with these two methods differed from those assessed more ecologically with the DLESP, and certain thought features were overrepresented in retrospective thought listing. Overall, our findings suggest that the TAP is as valid as the TPP for investigating spontaneous thought, although thought characteristics may differ between laboratory and real-world settings. They also suggest that concurrent reporting methods, such as the TAP and TPP, provide a more representative view of spontaneous thought features than retrospective assessments.