This study investigates the relationship between intelligence test performance, a test of visual inspection time (IT) and personality and temperament dimensions. Howe's (1990) hypothesis that IT and IQ are empirically related because of personality or temperament variables is evaluated and rejected. IT and performance IQ (PIQ) were significantly related independent of personality or temperament variables. IT and verbal IQ (VIQ) were unrelated. Robinson's (1989) hypothesis that ambiverts (moderate extraversion) perform significantly better on IQ tests was examined and supported. Ambiverts performed significantly better on verbal and performance measures of the Wechsler Adult Intelligence Scale–Revised (WAIS–R) and on the Raven's Advance Progressive Matrices (APM). Mobility from the Strelau Temperament Inventory (STI) was also related to performance IQ (PIQ) and Raven's test scores. These results suggest an important role for the concepts of arousal and/or arousability in a biological model of intelligence. Implications for intelligence assessment are discussed.