Five experiments, using a probe recognition procedure, examined the co
des involved in short-term memory. Interference effects were obtained
for probes with an orthographic, associative, or semantic relationship
to a memory set item. The orthographic interference effects appeared
to result from matches on the basis of abstract letter codes (i.e., gr
aphemes) rather than overlap of visual features. The associative and s
emantic effects differed from what might be predicted on the basis of
spreading activation, suggesting that these effects are qualitatively
different from semantic priming effects observed in lexical decision t
asks. These results support models of short-term memory in which items
are represented as groups of features and recognition depends on a co
mparison of the features of the probe to those of the memory set items
.