Reaction Time Distributions Across Normal Forgetting: Searching for Markers of Memory Consolidation

Volunteers studied pictures of objects and were then tested for yes/no recognition at 10 min and 1 week after learning (experiment 1), or at 10 min and 4 months after learning (experiment 2). Because the gradual consolidation of long-term memory is thought to occur across this time scale (weeks and months), the reaction time distributions of successfully retrieved items were analyzed in an attempt to detect markers of consolidation. At each retention interval, reaction times for items retrieved successfully were well fit by a model that assumed a single underlying distribution. No evidence for a bimodal distribution of reaction times was observed. Furthermore, there was no evidence that some small subset of items was actually retrieved faster after a long retention interval than after a short interval. The results are consistent with the idea that consolidation works not to increase memory trace strength but to change the nature of memory storage. This process occurs during the course of normal forgetting and may not be observable in the behavior of normal memory.