Any occasion on which an animal is placed in an experimental setting or con
text and receives pairings of one event with another provides the opportuni
ty for a variety of associative structures to be acquired. These structures
range from simple associations, which allow the presentation of one event
to activate or prime a memory of the other, to hierarchical associations, w
hich allow a simple association to he primed by some other event (e.g. the
context in which the simple association was acquired). Experiments with rat
s that reveal priming effects consistent with both of these putative associ
ative structures are reviewed.