A pilot investigation of "metaphor blindness" in a college student population

Previous research from our group suggests that patients with lesions in the left inferior parietal lobule (IPL)-which is concerned with abstract numerical cognition and cross-modal association (which is consistent with its strategic location at the crossroads between the temporal, parietal and occipital lobes) have difficulty understanding proverbs and metaphors (Ramachandran and Hubbard, 2001). In the current pilot investigation, we report "metaphor blindness" in a college student population; that is, either the complete inability or difficulty for otherwise intellectually non-challenged individuals to comprehend metaphors of language. Participants (N=205) read 12 metaphorical ("The detective jumped at the clue") and 12 literal ("The accident was a fall") sentences and had to decide whether the sentences conveyed a metaphorical or literal meaning. The mean accuracy for these metaphorical sentences was 11.0 (SD=2.3; RNG=0-12); the mean accuracy for literal sentences was 7.2 (SD=1.8; RNG=2-10). We found that 5% of participants (11/205) were unable or had difficulty understanding metaphors (i.e., were statistical outliers), while their score for literal sentences felt within a normal statistical range M=8.3 (SD=2.3; RNG=5-10). Follow-up control procedures were conducted in order to help ascertain that the results were not due to low verbal IQ and task difficulty. Likewise, none of the "metaphor blind" participants reported any psychiatric or neurological histories that would impair language comprehension, including strokes, brain injuries, language problems dyslexia, and signs of late language onset. The results are very preliminary and future studies are needed to confirm these findings. We suggest that brain modules may be specialized even for subtle functions like metaphor and their formation in embryogenesis may be controlled by small handfuls of genes whose expression can go awry--as in "metaphor blindness".