Ensemble Weakening and Behavior Generalization

Context dependent memory predicts better performance of a learned behavior when contextual cues remain consistent from practice to test, compared to that when the cues are changed. Several theories attribute this to the formation of a bond between the context cues and the new behavior. There is evidence in animal research however, that this bond may not be durable over time. Our hypothesis was that a reduction in the strength of this bond may be responsible for the ability to express a new behavior in different contexts after a longer retention interval. We tested this hypothesis by training our undergraduate participants (N = 60) to read a selection of inverted text under a particular set of context cues, then tested them in a new context either immediately or after one week. Immediate performance in the new context declined, but recovered after the 1 week interval. As all subjects still remembered what the original context was, we concluded that the increase in the new context performance over time was the result of a weakened relationship between the new behavior and the original context cues. ********** Characteristics of the environment (contextual features) present when new information is learned often benefit memory performance for that new information when they are also present at test. These contextual features include more local cues, such as the color of the paper on which words are printed (Dulsky, 1935), as well as cues like background music (Smith, 1985). Particularly when using recall tests, the more overlap between context encountered during learning and that present at test, the better memory performance (for a review see Smith, 1988). This benefit is referred to as context dependent memory (or as evidence of context effects) and is the definition of episodic memory. Several theorists have suggested that it may not be the presence or absence of context cues, per se, that influence memory, but it may be the overlap in the connection created between the to-be-learned information (or target) and contextual information (Baddely, 1982; Eich, 1985). Murnane, Phelps and Malmberg (1999) have referred to this connection as an "ensemble. " Although the concept of an ensemble was created to explain context effects in recognition memory, it is reasonable to believe that ensembles are formed when new mental or physical behaviors are learned, based on the contextual cues present during practice. Wright and Shea (1991) found context dependent memory effects on a computer task of motor skill learning when context cues present during practice were also present at test. Animal research on context effects has found a reduction in the degree to which a change in context cues degrades performance, when that behavior is tested over extended retention intervals. Perkins and Weyant (1958) demonstrated that rats trained on a runway of a certain color had immediately slower running times when that color was changed. After one week, the running speed of the rats was unaffected by a change in runway color. This pattern has been often repeated since (e.g., McAllister & McAllister, 1963; Thomas & Lopez, 1962; Zhou & Riccio, 1996), and is generally interpreted as evidence that while attributes of the learning experience (i.e., context cues) become associated with behavior during training, these attributes are forgotten more quickly than the new behavior itself. This forgetting allows the behavior to be effectively generalized to new situations. It is important to note that in all cases, the reduction of the difference between performance in new and old contexts is due to recovery in the different-context group over time. The same-context group's performance remains generally unchanged. With few exceptions, the fact that context memory effects are reduced over extended retention intervals has been overlooked in research on human memory. Balch, Bowman and Mohler (1992) found a decline in the detrimental effects of context change on an episodic memory test over a 48 hour interval. …