Open hands, large numbers: manual gestures influence random number generation.

Several studies suggest that numerical cognition interacts with spatial cognition. Here, we explored spatial-numerical associations through the lens of manual gestures. We asked English and Italian participants to generate 'random' sequences of numbers while simultaneously moving the hands outwards, away from the torso, or inwards, towards the mid center of the body. These manual gestures were modeled after gestures that are common in naturally occurring numerical discourse, such as when people talk about "huge numbers" or "tiny numbers." Results showed that in both participant groups, outwards movements coincided with relatively larger numbers compared to inwards movements, for which generated numbers were smaller. This effect was small in magnitude. We also explored individual differences and found that self-reported numeracy as well as levels of gesture production and perception modulated the effect of our gesture manipulation very little, if at all.