Adaptive repulsion of long-term memory representations is triggered by event similarity

ABSTRACT We tested whether similarity between events triggers an adaptive repulsion of long-term memories. Subjects completed an associative learning task in which objects were paired with faces. Critically, the objects consisted of pairs that were identical except for their color values, which were parametrically varied in order to manipulate interference. Performance on associative memory tests confirmed that color similarity robustly influenced interference. Separate tests of color memory showed that high similarity triggered a repulsion of long-term memories, wherein remembered colors were biased away from colors of competing objects. This repulsion effect was replicated across three experiments. In a fourth experiment, the repulsion effect was fully eliminated when task demands promoted integration, instead of discrimination, of similar memories. Finally, we show that repulsion of color memory was highly adaptive: greater repulsion was associated with less memory interference. These findings reveal that similarity between events triggers adaptive distortions in how events are remembered. SUPPLEMENTARY INFORMATION Three supplementary figures are included.