Temperamental reactivity includes behavioral and emotional reactivity. Behavioral reactivity includes impulsivity (defined as the speed of response initiation; Rothbart et al., 2001), shyness, and behavioral inhibition (slow or inhibited speed of approach and discomfort dealing with novel stimuli, including people; Kagan & Fox, 2006; Rothbart et al., 2001). Impulsive children appear to be pulled in an unthinking manner by their desires and potential rewards, whereas behaviorally inhibited children tend to be constrained, rigid, and inflexible in novel or stressful contexts. Behavioral reactivity can have an apparent regulatory effect on behavior in that it affects the approach to and the slowing and cessation of behavior. However, Eisenberg and colleagues (e.g., Eisenberg et al., 2004) and others (Derryberry & Rothbart, 1997; Nigg, 2000; Skinner & Zimmer-Gembeck, 2007) have emphasized the difference between willfully or voluntarily controlled aspects of control (including EC) and aspects of behavioral reactivity (or the lack thereof) that are less voluntary and more reactive. To highlight this distinction, Eisenberg et al. (2004) have labeled impulsivity and behavioral inhibition as aspects of reactive undercontrol and reactive overcontrol, respectively; this distinction
