wagner and heatherton : self-regulation and its failures 709 61 Self-Regulation and its Failures

The ability to flexibly alter behavior in the service of future goals is one of the key evolutionary adaptations that has enabled humankind to flourish. Self-regulation refers to a set of mental processes for overriding impulses, selectively attending to goal-relevant information, and monitoring thoughts and behavior for signs of failure. Although selfregulation is of fundamental importance to an individual’s success, failures of self-regulation are common. In this chapter we focus on the role of exposure to tempting cues, negative emotions, and limited cognitive resources in bringing about self-regulation failure. We review evidence from neuropsychology and functional neuroimaging that successful selfregulation depends on the interaction between brain structures in the prefrontal cortex involved in representing goals and directing attention away from goal-irrelevant stimuli and cortical and subcortical structures involved in representing the value of rewards during decision making. When the balance between these countervailing systems is disrupted as a result of overwhelming impulses, negative affect, or deficient top-down control, self-regulation failure ensues. More than any other species, humans are especially talented at controlling their own behavior in order to follow their goals and abide by rules and laws. Outside of certain psychiatric and neurological conditions, even the most impulsive human is still leaps and bounds more capable of not blowing off work, of not eating everything in the pantry, or of not stealing their spouse’s food than are the most precocious of nonhuman primates. Despite humankind’s enormous advantage in this domain, successful self-regulation remains difficult and failures are common (Baumeister & Heatherton, 1996; Wagner & Heatherton, in press). How is it, then, that humans are capable of inhibiting urges and pushing aside temptations in order to pursue their goals? One commonly held view is that humans have evolved specific mental faculties that allow for superior planning and behavioral flexibility. These adaptations underlie humans’ apparent superiority at self-regulation, and it has been hypothesized that they arose from a disproportionate amount of cortical expansion of the prefrontal cortex (PFC) over the course of human evolution (Rilling, 2006). Given the known role of the PFC in self-control, it was reasonable to assume that the brain would show specific structural changes to support these putative cognitive adaptations. However, recent work suggests that relative larger size of the PFC in humans compared to nonhuman primates may have been overstated (Semendeferi, Lu, Schenker, & Damasio, 2002). Instead, it has been suggested that, rather than overall size, the human PFC demonstrated increased white matter connectivity (i.e., Schoenemann, Sheehan, & Glotzer, 2005; although see Barton & Venditti, 2013). Regardless of whether the human PFC shows evidence of specialized morphological enlargement, that humans possess a unique capacity for planning and self-regulation compared to all other animals appears irrefutable. Or does it? Just how unique is the human capacity for self-regulation? Comparative psychological research on nonhuman primates and other animals has generally found that, with the exception of some domesticated animals (e.g., Miller, Pattison, DeWall, Rayburn-Reeves, & Zentall, 2010), most non-human animals display remarkably poor ability to inhibit prepotent responses in order to obtain later, larger rewards (i.e., delay of gratification). For example, most nonhuman animals, including many primates, will tolerate delays of only a few seconds before consuming a desired food item (Green, Myerson, Holt, Slevin, & Estle, 2004; Ramseyer, Pelé, Dufour, Chauvin, & Thierry, 2006). There are, however, some rare exceptions. For instance, great apes and some species of birds will tolerate delays as long as a few minutes provided the expected reward greatly exceeds the value of the currently available item (e.g., Beran, 2002; Dufour, Wascher, Braun, Miller, & Bugnyar, 2012). Given the studies discussed above, it appears that outside of certain primates and species of birds, evidence of self-regulation-like behavior is sparse among nonhuman animals. Why is it that humans have evolved this complex capacity to self-regulate? The importance of self-regulation for human social groups Unlike many animals, humans display a prolonged period of development and are unable to care for themselves for the first decade of life. Being a member of a social group brings with it tremendous advantages, from sharing the burden of child rearing to cooperative hunting and food sharing (Buss & Kenrick, 1998). As human safety and survival has long depended on living in groups, it has been suggested that humans have a