Concurrent consumption of cocoa flavanols and caffeine does not acutely modulate working memory and attention

Consumption of cocoa flavanols and caffeine might acutely enhance cognition, particularly in synergy. Due to the use of multifaceted tasks in prior research, it is unclear precisely which cognitive functions are implicated. We aimed to assess the acute effects of the (joint) ingestion of cocoa flavanols and caffeine on temporal attention, spatial attention, and working memory. In four separate sessions of a randomized, double-blind, placebo-controlled, crossover trial, our participants consumed a placebo drink, a drink containing cocoa flavanols (415 mg), a drink containing caffeine (215 mg), and a drink containing both concurrently. In each session, after ingestion, we tested performance in three cognitive tasks. We tested temporal attention in a dual-target rapid serial visual presentation paradigm, known to elicit the attentional blink, in which the lag between the targets was manipulated. We measured spatial attention in a visual search task, where we varied the number of distractors that appeared simultaneously with the target. We tested working memory in a delayed recall task, in which the number of stimuli to be maintained was manipulated. We obtained the expected performance pattern in each task, but found no evidence for modulation of response accuracy or response times by the ingestion of either substance, nor of their combined ingestion, even in the most challenging task conditions. We conclude that, even when jointly ingested, neither the tested amount of cocoa flavanols nor caffeine have acute effects that are robustly measurable on cognitive tasks that target attention and working memory individually.