Fluid intelligence allows flexible recruitment of the parieto-frontal network in analogical reasoning

Abstract

Fluid intelligence is the ability to think flexibly and to understand abstract relations. People with high fluid intelligence (hi-fluIQ) perform better in analogical reasoning tasks than people with average fluid intelligence (ave-fluIQ). Although previous neuroimaging studies reported involvement of parietal and frontal brain regions in geometric analogical reasoning (which is a prototypical task for fluid intelligence), however, neuroimaging findings on geometric analogical reasoning in hi-fluIQ are sparse. Furthermore, evidence on the relation between brain activation and intelligence while solving cognitive tasks is contradictory. The present study was designed to elucidate the cerebral correlates of geometric analogical reasoning in a sample of hi-fluIQ and ave-fluIQ high school students. We employed a geometric analogical reasoning task with graded levels of task difficulty and confirmed the involvement of the parieto-frontal network in solving this task. In addition to characterizing the brain regions involved in geometric analogical reasoning in hi-fluIQ and ave-fluIQ, we found that blood oxygenation level dependency (BOLD) signal changes were greater for hi-fluIQ than for ave-fluIQ in parietal brain regions. However, ave-fluIQ showed greater BOLD signal changes in the anterior cingulate cortex and medial frontal gyrus than hi-fluIQ. Thus, we showed that a similar network of brain regions is involved in geometric analogical reasoning in both groups. Interestingly, the relation between brain activation and intelligence is not mono-directional, but rather, it is specific for each brain region. The negative brain activation-intelligence relationship in frontal brain regions in hi-fluIQ goes along with a better behavioral performance and reflects a lower demand for executive monitoring compared to ave-fluIQ individuals. In conclusion, our data indicate that flexibly modulating the extent of regional cerebral activity is characteristic for fluid intelligence.

Keywords: functional magnetic resonance imaging; geometric analogical reasoning; high fluid intelligence; parieto-frontal network; task difficulty.

Figure 1

Geometric analogies. Examples of an analogy item (mirroring on the vertical axis in both pattern pairs; top) and a distractor item (mirroring on the vertical axis in the source pair and mirroring on the diagonal axis tilted to the left in the target pair; bottom). Note that the mirroring axes (red) were not displayed in the experiment.

Figure 2

Behavioral results color coded for the two groups. (A) Mean reaction times in millisecond (with SD) for the five levels of task difficulty (mirroring relation indicated by pictograms) and for both groups. (B) Mean reaction accuracy given as percent errors (with SD) for the five levels of task difficulty (mirroring relation indicated by pictograms) and for both groups.

Figure 3

Functional magnetic resonance imaging results. (A) Main effect of task difficulty, increases in BOLD signal changes with increasing task difficulty color coded in green. (B) Main effect of fluid intelligence for hi-fluIQ > ave-fluIQ color coded in blue. (C) Main effect of fluid intelligence for ave-fluIQ > hi-fluIQ color coded in orange. (D) Interaction of task difficulty and fluid intelligence color coded in blue.