Image of Hourglass. A cylinder measuring 11 cm x 27 cm was used to turn the animal upside down in the Hourglass setup. One trial period consisted of turning the cylinder 180°, causing the marmoset to be in a head-down position, to the moment the marmoset is once again in an upright position. Intervals between cylinder turn and the marmoset’s ability to recover its position (head above legs) was noted (righting time) with non-automated video analysis, done by an observer. Maximum time noted was 30 s (also for marmosets which did not turn upright at all). One test comprised 10 180° turns of the cylinder.