INDIVIDUAL DIFFERENCES IN INTELLIGENCE

Individual differences in intelligence in executive function



Individual differences in intelligence in executive function

An enduring enterprise of experimental psychology has been to account for individual differences in human performance. Recent advances in neuroimaging have permitted testing of hypotheses regarding the neural bases of individual differences but this burgeoning literature has been characterized by inconsistent results.

We argue that careful design and analysis of neuroimaging studies is required to separate individual differences in processing capacity from individual differences in processing speed to account for these differences in the literature. We utilized task designs which permitted separation of processing capacity influences on brainbehavior relationships from those related to processing speed. In one set of studies, participants performed verbal delayed-recognition tasks during blocked and event-related fMRI scanning.

Studies of WM date back to the 1880s when Ebbinghaus (1885) pioneered the use of nonsense syllables to study learning and forgetting in controlled experiments. Through his research, Ebbinghaus found that he could correctly recall seven syllables after just one reading. James (1890) introduced the term “primary memory” to represent the cognitive construct responsible for temporary maintenance of information. He explained that images in primary memory are lost forever unless they are consciously sustained in the mind for a sufficient period of time. More than half a century later, Friedman (2006) proposed the term “immediate memory” and described its capacity as 7±2 units or “chunks” of information, which is consistent with Ebbinghaus' finding on temporary memory capacity. As cognitive psychology developed, research provided more detailed understandings of memory.

Atkinson and Shriffrin (1968) proposed a memory model which included a sensory store, short-term memory (STM), and longterm memory (LTM). According to their model, incoming information was first registered in the sensory store. A limited amount of this information was attended to and passed onto STM; information not attended to was lost. STM was viewed as a capacity-limited, unitary memory store which temporarily kept information for further processing. Information in STM decayed after two seconds if not rehearsed. (Friedman 2006) Rehearsed information was encoded and saved in LTM, an unlimited store that retained information for long periods. Information relevant to a cognitive task could be retrieved from LTM at a later time. Memory researchers recognized that theories of STM could not adequately describe the kind of temporary memory that complex cognitive tasks require.

Eventually, memory research gave rise to theories in which STMwas seen as one component of a larger system known asWM.Researchers proposed different theories to demystify WM, including models focusing on the structure and function of WM. These models provided different but complimentary views of WM and contributed to a comprehensive understanding of WM (Engle, et al. 1999).

Psychologists have acknowledged for a long time that the capacity of WM is limited, that is, one can only process a few amount, not every piece, of information at every moment. This phenomenon can be easily observed from the decline of the recall accuracy while another mental process is ...