Using the landmark task to test the underlying assumptions of unilateral contraction research

The unilateral contractions procedure (i.e., squeezing a ball with one hand) supposedly enhances a wide variety of cognitive functions, from episodic recall to choking under pressure. The practicality and affordability of this procedure makes it highly appealing. But does it work? We addressed this question by testing whether intermittent and sustained unilateral contractions shifted a well-supported hemispheric asymmetry: visuospatial attention. Based on prior research, contracting the left (or right) hand should lead baseline scores on the landmark task-a visuospatial attention measure-to deviate further left (or right). We meta-analysed the results of our six experiments and showed that the unilateral contractions procedure, particularly with intermittent contractions, does not reliably shift landmark task scores measured during (Experiments 4-6) or after (Experiments 1-3 & 6) performing unilateral contractions. Although we question if and how unilateral contractions activate the contralateral hemisphere, Experiment 6 provided some support for the utility of sustained contractions.