Reinforced variability enhances object exploration in shy and bold rats.

In an open-field test, the Long-Evans (LE) strain of rats was identified as "bold" and the PVG strain as "shy." Some members of each strain then experienced 14 sessions of a common enrichment procedure, namely exposure to a series of novel objects (Exposed). Others in each strain were explicitly reinforced with food pellets for variable interactions with the same objects (Reinforced). Both experience and strain influenced object interactions. In particular, Reinforced rats interacted more variably with the objects - contacting, probing, pushing and so forth - than did the Exposed; and LEs interacted more variably than PVGs. Foraging proficiency in the same rats was then studied in a transfer-of-training test. Food pellets were hidden among never-before experienced objects and the rats were permitted to explore freely. Reinforced rats discovered and consumed more pellets than Exposed; and LEs discovered and consumed more than PVGs. Thus a bold genetic strain and reinforcement of variability independently contributed to successful foraging behavior.