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Geotaxis of infant rodents: Think positive.   J.R. Alberts.  Department. of Psychological and Brain Sciences, Indiana University, Bloomington, IN.

   Traditionally, infant rodents have been characterized behaviorally as displaying “negative geotaxis”, i.e., a reflex-like tendency to orient and move directionally against gravity, such as up an inclined plane.  Recent re-evaluations and experiments indicate that this tradition is patently incorrect.  Previous reports of negative geotaxis by young rodents are unreliable or, in many cases, appear to describe postural adjustments or other compensatory responses to prevent falling.   If rat pups are geotaxic at all, they display positive, not negative geotaxis.  10-day-old rat pups placed on modest inclines (e.g, 4^o) moved downhill (positive geotaxis), but their downward orientation required contact with a wall.  Such wall contact was subsequently associated with greater velocity of movement.  A broader and more integrative view of a young rodent’s gravity-guided responses is needed, because thigmotaxis and orthokinesis may also be involved.  These findings will be discussed in the context of research and testing in gravitational and space studies.