Fig. 3: Perceptions of (a) agreeableness and (b) dominance during tryptophan and placebo phases of treatment (values are estimated least squares means and standard errors). The horizontal axis crosses the vertical axis at 6 to indicate the middle of the individual axes on the interpersonal grid. Tryptophan increased perceived agreeableness in others in men who received tryptophan second (*p = 0.019). Tryptophan also increased perceived dominance in others (**p < 0.001).