This paper reports our finding of the use of a proposed biological code - the size code in anger and joy speech. In searching for explanations for an F0 peak delay phenomenon related to angry speech that cannot be accounted for by known articulatory constraints, we hypothesized that the delay was due to the lowering of the larynx to exaggerate body size, a biological code known to be used by animals. Our analysis of the formant frequencies in existing emotional speech databases revealed that anger speech had lowered formants and joy speech had raised formants. The results confirm our hypothesis and suggest that the size code is being actively used by humans to express emotions.