Individual differences in automatic semantic priming

This research investigated whether automatic semantic priming is modulated by individual differences in lexical proficiency. A sample of 89 skilled readers, assessed on reading comprehension, vocabulary and spelling ability, were tested in a semantic categorisation task that required classification of words as animals or non-animals. Target words were preceded by brief (50 ms) masked semantic primes that were either congruent or incongruent with the category of the target. Congruent primes were also selected to be either high (e.g., hawk EAGLE, pistol RIFLE) or low (e.g., mole EAGLE, boots RIFLE) in feature overlap with the target. ‘Overall proficiency’, indexed by high performance on both a ‘semantic composite’ measure of reading comprehension and vocabulary and a ‘spelling composite’, predicted stronger congruence priming from both high and low feature overlap primes for animal exemplars, but only predicted priming from low overlap primes for non-exemplars. Classification of high frequency non-exemplars was also significantly modulated by an independent ‘spelling-meaning’ factor, indexed by differences between the semantic and spelling composites, which appeared to tap sensitivity to semantic relative to orthographic feature overlap between the prime and target. These findings show that higher lexical proficiency predicts stronger automatic semantic priming and suggest that individual differences in lexical quality modulate the division of labor between orthographic and semantic processing in early lexical retrieval.Australian Research Counci

The Effects of Mental Abacus Expertise on Working Memory, Mental Representations and Calculation Strategies Used for Two-Digit Hindu-Arabic Numbers

In Asia, some children are taught a calculation technique known as the ‘mental abacus’. Previous research indicated that mental abacus experts can perform extraordinary feats of mental arithmetic, but it disagrees as to whether the technique improves working memory. The present study extended and clarified these findings by contrasting performance from several numerical and working memory tasks across three groups of participants: Japanese mental abacus experts, abacus-naïve Australian undergraduates, and abacus-naïve Japanese undergraduates. It also investigated whether the mental representations and strategies used to process two-digit numbers differed across the three groups. First, the results showed that the Japanese mental abacus experts only performed better when the numerical and working memory tasks involved arithmetic problems, suggesting domain-specific transfer rather than domain-general improvements to numerical processing or working memory. Second, the results suggest that the Japanese mental abacus experts were less reliant on decomposed magnitude representations, and used a processing strategy that is less sensitive to the perceptual overlap between numbers. Finally, performance was less discrepant between the Australian and Japanese abacus-naïve undergraduates than either group with the Japanese mental abacus experts, indicating that mental abacus training, rather than socio-cultural differences, was responsible for the observed group differences

Thinking Digitally: Individual Differences in Mental Representations of Number and Computational Algorithms Associated with Exact Quantities

The present research explored mental representations of number, the computational algorithms used to solve multi-digit arithmetic tasks, and how mental manipulation of exact quantities are modulated by individual differences in working memory capacity and method of instruction through six experiments. The first three experiments focused on holistic or decomposed mental representation of 2-digit numbers in Australian university students using a magnitude judgement and number bisection task. Since holistic or decomposed magnitude representations are associated with different multi-digit addition algorithms, Experiment 4 investigated individual differences in orthographic precision and strategies for multi-digit addition using a same-different mental arithmetic task. Experiment 5 explored the relationship between working memory and construction of novel strategies in a mathematical problem solving task using Diophantine equations. Individual differences in mental representations were further explored in Experiment 6 by comparing Australian university students with Japanese children who were skilled users of a ‘mental abacus’. Although the Japanese children’s performance was superior to the university students on virtually all tasks, both groups appeared to use qualitatively similar strategies of computing the total of 2-digit numbers by decomposing each of the operands according to unit and decade positions. Why are some people better at maths than others? The results suggest that computational speed and accuracy were associated with larger working memory capacity, stronger decomposed mental representations of number, and an educational approach that involved plenty of practice. All of these attributes facilitate application of exact multi-digit algorithms. Aside from the theoretical implications of these findings for the field of numerical cognition, the results are also practically important for teachers and policy makers