I have elsewhere asserted that the executive functions likely evolved in successive stages in our hominid ancestry from intra-species competition for resources and reproduction in our group living species. The sequence may resemble, to some extent, the same sequential development evident in children today. The first executive function (sensory-motor action to the self, especially visual imagery) begins its development so early in infancy that it must have been crucial to human survival. It may have evolved for the adaptive purposes of reciprocal altruism (social exchange) and generalized vicarious learning. These activities seem to be essential for the survival of our group living species, contributing to reciprocity, cooperation, coalition formation (friendships), the construction of social hierarchies from these coalitions, and pedagogy (Barkley, 2001c, 2012d). Vicarious learning can be considered a form of behavioral plagiarism that, once having arisen in a species, would have set up strong selection pressure for the privatization of one’s behavior, particularly during learning, rehearsal, and other forms of practice, so as not to have one’s behavioral innovations readily appropriated by others (competitors). Other adaptive purposes that may have been served by this and the other three executive functions that develop later are verbal self-instruction, verbal self-defense against social manipulation by others, and self-innovation during social competition. Such evolutionary speculations permit this theory to hypothesize various social deficits that should be evident in ADHD given the executive deficits associated with it that can be tested in subsequent experiments. As is evident below, children with ADHD experience serious difficulties in their social relationships, some of which may arise from the deficits in executive functioning that interfere with reciprocal exchange, vicarious learning, social coalition formation, social self-defense, and self-innovation (improvement).
Possible neurotransmitter dysfunction or imbalances have been proposed in ADHD for quite some time (see Sagvolden, 2005; Pliszka, McCracken, & Maas, 1996 for reviews). Initially, these rested chiefly on the responses of ADHD children to differing drugs. ADHD children respond remarkably well to stimulants, most of which act by increasing the availability of dopamine via various mechanisms, and producing some effects on the noradrenergic pathways as well (Connor, 2006). Consequently, it seemed sensible to hypothesize that these two neurotransmitters might be involved in the disorder. Given the findings that normal children show a positive, albeit lesser, response to stimulants (Rapoport et al., 1978), however, partially undermines this logic. Other, more direct evidence comes from studies of cerebral spinal fluid in ADHD and normal children that indicated decreased brain dopamine in ADHD children (Raskin, et al., 1984). Similarly, other studies used blood and urinary metabolites of brain neurotransmitters to infer deficiencies in ADHD, largely related to dopamine regulation. Early studies of this sort proved conflicting in their results (Shaywitz, Shaywitz, Cohen, & Young, 1983; Shaywitz, Shaywitz, Jatlow, et al., 1986; Zametkin & Rapoport, 1986). A subsequent study continued to find support for reduced noradrenergic activity in ADHD as inferred from significantly lower levels of a metabolite of this neurotransmitter (Halperin et al., 1997). What limited evidence there is from this literature seems to point to a selective deficiency in the availability of both dopamine and norepinephrine, but this evidence cannot be considered conclusive at this time. Far greater evidence for involvement of these and other neurotransmitters comes from the rapidly growing evidence for the role of gene polymorphisms involved in regulating these neurotransmitters that reveals different gene variations in ADHD than in typical population samples (for reviews, see Banaschewski et al., 2010; Smith et al., 2009; Wu et al., 2012).
3. Given that the model hypothesizes a deficit in internally generated and represented forms of motivation that are needed to drive goal-directed behavior, those with ADHD will require the provision of externalized sources of motivation. For instance, the provision of artificial rewards, such as tokens, may be needed throughout the performance of a task or other goal-directed behavior when there is otherwise little or no such immediate consequences associated with that performance. Such artificial reward programs become for the ADHD child like prosthetic devices such as mechanical limbs to the physically disabled, allowing them to perform more effectively in some tasks and settings with which they otherwise would have considerable difficulty. The motivational disability created by ADHD makes such motivational prostheses nearly essential for most children with ADHD.
Money Management. Individuals who are more impulsive, have a penchant for immediate gratification and discount future consequences, and are generally poorer at self-regulation can be expected to have problems managing their finances. Given that these characteristics typify adults with ADHD, we hypothesized that those adults would have considerable problems managing money. Our hypotheses were largely borne out. The adults with ADHD in the UMass Study had a higher proportion of its members reporting problems with managing money, saving money, buying on impulse, nonpayment of utilities resulting in termination, missing loan payments, exceeding credit card limits, having a poor credit rating, and not saving for retirement. Relative to the normal control group, the adults with ADHD appear to be having relatively pervasive problems with the management of their finances. Several areas of money management were specifically elevated in the ADHD group more than in both the clinical and community control groups – deferred gratification (saving and putting money away for retirement), impulse buying, and meeting financial deadlines (nonpayment of utilities resulting in their termination). On all six frequency measures of money management, the adults with ADHD reported more difficulties more often than did the adults in our community control group. Money difficulties were also more common in the ADHD than in the clinical control group in at least four of these six areas – missing rent payments, missing utility payments, missing loan payments, and having more total money problems. Numerous financial problems were also associated with the hyperactive group in the Milwaukee Study, though these were most frequent in that group whose ADHD had persisted until age 27. Both studies have found a clear, robust, and specific relationship of adult ADHD to a diversity of financial problems, regardless of how adult ADHD patients were ascertained (clinic-referred or children followed to adulthood).
2. Eliminate or decrease caffeine, especially for children. Adults may find that caffeine helps control ADHD symptoms, and there is some evidence to support this hypothesis. For children, however, the risks associated with excess caffeine consumption are just too great — particularly when combined with the high sugar levels often found in energy and soft drinks.