Is there a graph with extroversion-introversion score on one axis and IQ on the other? I can't find one on Google Images.
Extraversion and IQ typically have zero correlation. In Bates and Rock (2004),we suggested that if the arousal value of the testing environment varies, this might induce a modest correlation with IQ (introverts doing best in silences, ambiverts with some noicse, and extraverts performing best under fairly loud white noise background. More basic measures like inspection time were unaffected.



Based on some followup queries, here's a graph of Extraversion against IQ-score in 597 adults from a normative sample in the United States: The MIDUS.

The plot shows the raw data points, and also a loess best fit curve: no relationship, even at the extremes.