Interference Control in Memory and Fluid Intelligence

This thesis investigated the role of interference in general cognitive functioning. Study 1 explored the relationships among interference control, memory, and fluid intelligence. Studies 2 and 3 explored the possibility that interference is controlled by suppressing the interfering information rather than, for example, facilitating the target information. Study 1 tested the hypothesis that individual differences in the ability to regulate interference are responsible for the correlation between memory tasks and fluid intelligence. Participants completed common measures of working memory, long-term memory, fluid intelligence, and interference regulation. In structural equation models, controlling for interference regulation ability largely accounted for the correlation between the memory tasks and fluid intelligence. These results suggest that efficient interference control is critical to cognitive functioning. Study 2a tested the hypothesis that interference is regulated by suppressing competing responses. In Phase 1 of a three-phase paradigm, participants performed a vowel-counting task that included pairs of orthographically similar words (e.g., allergy/analogy). In Phase 2 participants solved word fragments (e.g., a _ l _ _ gy) that resembled both words in an earlier pair, but could be completed only by one of these words. Phase 3 measured the consequence of having resolved interference in Phase 2 by asking participants to read a list of words, including the rejected competitors, as quickly as possible. Relative to participants in control conditions that did not require interference resolution these interference condition participants were slower to name competitor words. Study 2b showed that while competitors are suppressed during interference resolution, a complementary facilitative process does not directly enhance accessibility of targets. Finally, Study 3 tested the hypothesis that older adults have impaired suppression abilities. Older adults were tested in the same paradigm used in Studies 2a and 2b. In contrast to younger adults, older adults showed no suppression of competitors. This result supports the theory that some age related memory deficits stem from impaired suppression processes.Ph