Paying attention to newly learned semantic codes.

Most investigations of semantic memory treat it as a static system with a relatively fixed organization. It seems clear, however, that people continue to add facts and to expand their organized semantic knowledge across most or all of the lifespan. This talk made four points concerning the acquisition of new semantic knowledge.First, fully integrated new information into semantic memory is arduous and time consuming. For example, it is well known that overlearned associations such as "car - truck" or "doctor - nurse" produce automatic priming in tasks like lexical decision. Facilitation from a related prime occurs at prime - target SOAs of 200 ms or less in the absence of any specific explanations that primes and targets will be related. One might take a new fact's ability to produce automatic priming as a criterion for full integration into semantic memory. Dagenbach, Horst, and Carr (1990) did this and found that five weeks of daily practice were sufficient to fully integrate a new fact, even though the fact was consistent with already established knowledge and merely extended existing categories. In this study, the new facts were previously unfamiliar vocabulary items such as "accipiter - a kind of hawk" or "drupe - a cherry", and priming was sought from the newly learned word to a semantic associate of the definition, such as "accipiter" as a prime for "eagle". In contrast, five weeks of daily practice were not sufficient to fully integrate a new arbitrary association that altered or went against the already - established organization of semantic memory, such as pairing "car" with "nurse" or "doctor" with "truck".If it takes a long time to integrate a new fact with the semantic network sufficiently for its activation to become automatic, one might wonder whether any special problems arise in trying to find and use the new fact early in this process, before integration is completed. The second point of the talk was that early in learning, a weakly established semantic code is likely to suffer competition from older, stronger codes, making it difficult and effortful to retrieve.The third point of the talk was that an attention mechanism that works on the center - surround principle could be very helpful in these circumstances, facilitating retrieval of weak codes by actively suppressing their stronger competitors. The ideal that attention might work by a combination of facilitation and inhibition has a long history in cognitive science. In particular, the center - surround notion was discussed as a mechanism for retrieval from semantic memory by Walley and Weiden (1973).The final point was that evidence for a center - surround attention mechanism has been observed in the form of inhibitory semantic priming in training studies that involve vocabulary acquisition and shape categorization. New vocabulary words were taught whose definition placed them into already existing semantic categories, or artificial object categories were taught by exposing subjects to arbitrarily composed sets of unfamiliar visual shapes. Then, in a subsequent task requiring either lexical decision or shape categorization, newly taught words or newly exposed shapes as well as already familiar words or more heavily practiced shapes were used as primes. The prime - target SOA was relatively long (2000 ms), giving subjects time to try to retrieve the prime's meaning before the target appeared. …