The organization of arithmetic facts in memory: evidence from a brain-damaged patient

We report a single case study of a brain-damaged patient with impaired arithmetic performance. Three principal findings are presented: First, in a task involving production of answers to simple arithmetic problems, the patient's performance was far better for subtraction than for addition or multiplication. Second, in all arithmetic operations performance was generally much better for problems potentially solvable by rule (e.g., 5 + 0) than for problems requiring retrieval of specific facts (e.g., 5 + 3). Third, the dissociation between subtraction and the other arithmetic operations obtained in the production task was not observed in a verification task. The implications of these findings for claims concerning the organization of stored arithmetic facts are discussed.     

Semantic priming and repetition priming from masked words: Evidence for a center-surround attentional mechanism in perceptual recognition.

Two lexical decision experiments compared semantic and repetition priming by masked words. Experiment 1 established prime–mask stimulus onset asynchronies (SOAs) with presence–absence detection judgments. Primes presented at detection-threshold SOAs produced equal facilitation for repeated and semantically related targets: 26 ms and 24 ms. Experiment 2 established SOAs with semantic judgments. Primes presented at 70% of the semantic-threshold SOA to mimic the exposure conditions of Experiment 1 produced slightly greater facilitation for repeated targets but a tendency toward inhibition for semantically related targets: 38 ms and –6 ms. These results confirm the D. Dagenbach et al (see record 1990-00392-001) report that strategies induced by threshold-setting tasks can influence masked priming. In addition, Experiment 2 suggests a mechanism for retrieving weakly activated semantic codes into consciousness that relies on the center-surround principle to enhance activation of sought-for codes and to inhibit related codes stored nearby in the semantic network. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inhibitory semantic priming of lexical decisions due to failure to retrieve weakly activated codes.

Semantic priming effects from newly learned vocabulary words are examined in a lexical decision task. At low levels of learning, those primes whose meanings are recognizable but not recallable can inhibit responses to well-known, semantically related target words, whereas those whose meaning are recallable produce either no effect or facilitation, depending on instructions concerning how to use the prime information. These results are consistent with the notion that semantic priming effects are determined at least in part by the nature of the retrieval operations performed on the prime and target, over and above influences due to spreading activation and confirmed or violated expectations. Specifically, they indicate a need to include mechanisms other than violated expectations that can produce inhibition of retrieval. Candidate mechanisms are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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. 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 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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adding new information to semantic memory: How much learning is enough to produce automatic priming?

A series of experiments investigated the integration of new vocabulary words into semantic memory and the creation of new associations between preexisting, but previously unrelated, words. The ability of the newly learned vocabulary words and associations to facilitate lexical decisions when serving as primes under conditions associated with automatic processing was used to index integration. The results indicate that very extensive study is necessary for such integration to occur and that it is easier to add a new word to semantic memory than to establish a link between two formerly unconnected words already in semantic memory. The implications of these results for models of semantic memory and the episodic/semantic distinction are considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)