The limbic system determines the salience of environmental stimuli and the prefrontal cortex chooses which reactive impulses to suppress and which to give rein. Primarily, the function of impulse suppression is to reduce time preference so that larger, later payoffs are preferred over smaller, sooner payoffs. Attention Deficit Disorder is best explained, in general, as a simple matter of high time preference (inability to suppress impulses and defer gratification) indicating retardation in the cerebral cortex, or limbic dysfunction such that salience is determined inappropriately. The latter will often correspond with sexual dysfunction and extreme mutation accumulation.
However, this is an incomplete model if we consider the curious paradox of ADHD-Inattentive people, who occasionally exhibit hyperfocus and produce feats of unbelievable self-inhibition, on an entirely different scale of magnitude than ordinary feats of low time preference. For example, only people with ADHD-I are capable of the legendary marathon coding sessions that Scrum attempts to replicate.
This paradox cannot be fully explained by the ADHD-I person finding the code more interesting than schoolwork, or by value stratification, because a person in a state of hyperfocus famously ignores their physical interests such as hunger. If the phenomenon were purely a matter of poor impulse control, then it would be interrupted by other impulses such as hunger as these increased in magnitude. Instead, we observe that if given a binary choice between satisfying physical needs (eating, sleeping, socialization, relaxation, etc.) and finishing the project, the ADHD-I person will often elect the latter and suffer physically in order to realize his future vision of the finished product. In the same individual, we have a contrast between generally low impulse control and occasionally superhuman impulse control.
Therefore I suggest that ADHD-I is not a simple impulse control problem indicating retardation in the cerebral cortex, but rather a core difference in the limbic system. I propose that it is a misdiagnosis of the endogenous personality type in combination with high impulse control.
The exogenous personality type is primarily concerned with social success because this is the correct strategy among primates, who allocate resources according to hierarchical position. An exogenous personality with low time preference will prefer high-effort, high-reward strategies such as academic performance, SAT test preparation, and researching possible career paths that will offer a maximum return on prestige for effort. By contrast, an exogenous personality with high time preference will rationalize that life probably does not continue after the age of 29.
The endogenous personality type cannot be explained this way, and the disinterest in pursuing social success is misdiagnosed as a lack of impulse control because the social effects are similar. However, the immediate appearance is very different—where a person lacking impulse control will attend to external stimuli heedlessly, the ADHD-I personality sits quietly and appears to attend to nothing at all. Except, occasionally, when they unexpectedly take an superhuman interest in stimuli related to some internal motivation.