Individual differences in digit span, susceptibility to proactive interference, and aptitude/achievement test scores

Individual differences in digit span, susceptibility to proactive interference, and various aptitude/achievement test scores were investigated in two experiments with adults. Susceptibility to proactive interference was estimated from performance in a position task in Experiment 1, and from the Brown-Peterson task in Experiment 2. In contrast to previous research, digit span was strongly correlated with many of the aptitude/achievement scores in both experiments, suggesting that the digit span task taps some important components of mental ability. The results of both experiments were also consistent in offering no support for the hypothesis that susceptibility to proactive interference is an important source of span differences. Finally, the results of Experiment 2 suggest that susceptibility to proactive interference is a source of individual differences in reading comprehension and knowledge of word meanings, but not in grammar and word usage skills, reading rate, or quantitative ability.