To investigate the facilitative effects of an olfactory-masticatory composite N-back training paradigm on working memory in healthy adults.

Chewing gum containing 1, 8-cineole and up to related safety standards was developed before a composite training protocol incorporating this gum was designed. Sixty-three healthy adults were randomly assigned to either a composite-stimulation training group (n=33) or a single-modality training group (n=30). Participants in the composite-stimulation group chewed gum containing 1, 8-cineole in the process of performing training tasks for three consecutive days while the single-modality training group completed the tasks without chewing gum. Working memory performance was evaluated before and after the intervention using spatial and digit N-back tasks, while cognitive control transfer was evaluated using a Stroop task.

Compared to the single-modality training group, the composite-stimulation group was significantly more accurate and shorter in reaction times during the high-load working memory task (specifically, the spatial 5-back task; P < 0.05), and exerted more pronounced near-transfer effects in the digit 3-back task (P < 0.05). However, no additional benefits were observed in the Stroop task, suggesting that the composite intervention did not deliver significant far-transfer effects.

The combination of olfactory-masticatory stimulation with N-back training can significantly enhance high-load working memory and enhance near-transfer effects. This approach offers a simple, quick, and broadly applicable approach to cognitive enhancement.