n. the tendency to accept risk, a dimension of temperament observed in both humans and nonhuman animals. Thus, a bold preschooler may freely engage with unfamiliar classmates, and a bold rat may explore all available areas during an open-field test. Individual differences in boldness are presumed to arise from differences in the excitability of areas of the limbic system that are involved in the evaluation of stimulus saliency. For example, bold adults exhibit more bilateral nucleus accumbens activation and less bilateral amygdala activation when looking at the faces of strangers than do less bold adults. Compare shyness. See also shy–bold continuum.