- Like many brain functions, motivational circuitry operates as a circular feedback loop, with bottom-up and top-down pathways.
- People differ greatly by temperament in their typical level of motivation and how much reward they need in order to keep them motivated.
- Sustaining motivation is tied to the ability to sustain focus and goal-directedness—abilities dependent on the strength of executive function.
Mark, an intelligent and engaging 21-year-old, came to see me for a psychiatric consultation to try to figure out why he kept running into difficulty achieving his goals. He seemed only willing or able to sustain effort for tasks that were highly stimulating or novel, or where there was some significant (and preferably immediate) reward or consequence. He was reattempting university after having twice dropped out in first year, despite his interest in his chosen field. A smart but easily bored student, he started out with full intention to do all the readings but quickly ran into difficulties maintaining motivation as the material became more detailed and as the workload mounted. He also had difficulties adhering to routines of self-care and completing basic chores. His room was a huge mess. He had difficulty maintaining a regular sleep-wake schedule, staying up too late watching Netflix movies and YouTube videos. Both he and his parents were frustrated by his chronic inability to sustain motivation despite his intention and stated commitment to achieve his goals.
Mark is representative of a large swath of the population with similar motivational difficulties.
How motivation works in the brain1
A lot is understood about the brain’s motivational circuitry, also referred to as the "reward" circuit. Like many brain functions, it operates as a circular feedback loop, with bottom-up and top-down pathways. You could say that the bottom-up pathways, which are automatic, serve to drive or fuel motivation, while the top-down pathways, which are more deliberate, serve to focus, direct and control motivation. The bottom-up pathways, emanating from the primitive brainstem, assign relative weight or importance to sensory inputs, responding more strongly to novel and salient signals, thereby alerting attention and activating feelings of reward (other bottom-up pathways respond rapidly to threat). The top-down pathways, emanating from the brain’s more evolved outer cortical regions (specifically the prefrontal cortex or PFC, which is the “highest,” most evolved part of the brain—located behind your forehead) have the crucial role of regulating the responsiveness of the bottom-up pathways, and of controlling behavior. The top-down pathways also incorporate learning from past experience, through behavioral conditioning mechanisms. The system as a whole is known as the mesocorticolimbic circuit.2
Motivational processes involving reward consist of two main elements: “wanting” and “liking”—anticipation of reward and enjoyment of its attainment.3, 4 These two elements have partly divisible brain networks and neurotransmitters.5, 6
Why do some people have a harder time staying motivated?
People differ greatly in their typical level of motivation, particularly for less stimulating, less immediately rewarding tasks. They differ in how much reward they need in order to keep them motivated (this is mostly a function of the bottom-up pathways). And they differ greatly in their level of self-control and ability to sustain focus and goal-directedness—abilities that are dependent on the strength of “executive function,” which is a set of top-down functions of the prefrontal cortex. Executive function basically accounts for what we commonly think of as self-control, self-discipline, and willpower.7 These traits also correlate with the personality dimension of conscientiousness, one of the Big Five personality traits.
Like most traits, the variability in executive function (or, similarly, conscientiousness) in humans can be represented graphically by a bell curve, with people at both tails of the curve more likely to be hampered by their too-low or too-high strength of executive function. People with less strong executive function have difficulty sustaining focus and motivation for unstimulating activities, difficulties with organization, planning, self-control/self-regulation, and related issues. This profile is practically synonymous with ADHD (with or without hyperactivity). Less obviously, people whose executive function is too “tight” also quite often have difficulties – they may be too controlled, perfectionistic, too intense, “workaholic,” not easily able to unwind and have fun (they may also be prone to certain mental disorders, such as anorexia nervosa).8 Individual differences in executive functions have been found to be almost entirely genetic in origin.9 This does not mean that these functions are rigidly fixed for life—environment has an effect on optimising or impairing a person’s inborn potential, and training can improve these skills, to a degree.
People whose reward circuits require more stimulation
Several brain chemicals play key roles in the motivation/reward circuit, particularly dopamine. There is evidence that the dopamine reward system in people who meet criteria for ADHD might be tuned at a lower level than other people.10ADHD may be simply that part of the spectrum of the population who have “reward circuits that are less sensitive at baseline than those of the rest of us,” as psychiatrist Richard Friedman puts it. “Having a sluggish reward circuit makes normally interesting activities seem dull and would explain, in part, why people with ADHD find repetitive and routine tasks unrewarding and even painfully boring.”11 In a sense, brains on the ADHD end of the spectrum are less internally stimulated, requiring greater external stimulation to hold their attention and motivate them.12 Mark, for example, had no difficulty staying motivated in his sports and in his stock trading pastime, at which he was quite successful.
One of the things our brain does, often unconsciously and automatically, when facing the prospect of expending effort on a task, is a cost-benefit computation. Some people, especially those with ADHD traits, tend to discount distant future rewards, in this computation.13
The fact that so many people today, just like Mark, struggle to maintain focus and motivation for less stimulating tasks is partly a result of the fact that modern societies have created a very artificial environment that is highly structured and organized, with division of labor into highly specialized tasks requiring sustained effortful focus, attention to detail, organization, patience, self-discipline and the ability to work toward very delayed or abstract rewards. This is nothing like the Paleolithic environment in which our hunter-gatherer ancestors lived for the great majority of our species’ evolutionary history.
Of course, even for those of us who generally have an easier time sustaining focus and motivation, a great many other factors cause our motivation to wax and wane over time.14 A few of the obvious ones are fatigue, hunger,15 frustration, feeling overwhelmed by a task, burn-out, demoralization, lack of confidence, feelings of failure, feeling devalued, or perceiving a task to be pointless or effort to be futile.
Episodic disorders and progressive diseases that impair motivation
There are disorders and diseases that more severely and persistently impair motivation in a person who may otherwise have been previously motivated. These include depression—which usually occurs in episodes and then improves, schizophrenia—which may be more enduring and progressive in the untreated state, and dementia—which is typically severely and relentlessly progressive and irreversible. Brain injury, especially if it affects the frontal lobes, can also profoundly impair motivation. So can a variety of other disorders and illnesses.
Addictions, in contrast, hijack and commandeer the brain’s reward system and redirect it to the repeated acquisition of the addictive substance.16
The question of free will
Understanding the brain mechanisms of motivation leads us to the inevitable question of whether or to what degree we have “free will.” From a scientific point of view, there can be no such thing as true free will in the pure philosophical sense of the term, since everything in the universe, including the processes in the brain, is governed by cause-effect mechanisms.17 The mind cannot act in ways that are untethered from the determining causes of its physical constituents. Those causes involve gene-environment interactions.
The “mind,” by which we basically mean “what the brain does,” functions within a reciprocal feedback loop or reverberating circuit—a cybernetic loop. The brain is an elaborate stimulus-response organ. In neuroscientific terms, "free will" only makes sense in terms of relative degrees of mental flexibility. Mental disorder, itself a matter of degree, constrains that flexibility. Even in the absence of disorder, as we have seen,18 there is much variation between brains in how flexibly they respond to stimuli and in their ability to “will” themselves to do effortful tasks.
Nevertheless, it is reasonable to use the term “free will” in practice, given the vast complexity of the variables that determine human thought and behavior and the (probably inherently) unpredictable nature of complex emergent systems like the mind. The vast combinatorial power and many degrees of statistical freedom resulting from such a complex interplay of myriad physical variables creates a very satisfying illusion of free will. For practical purposes, it is as if we have free will, and we can regard ourselves as having such.
Mark eventually succeeded in getting through his university studies. He even did quite well, with the help of an executive function coach, academic accommodations, the steady reinforcement of better lifestyle routines, and more effective study habits tailored to his learning style. After trying his hand at a few jobs, he found himself in corporate finance, a career suited to his need for frequent novelty, reward, and stimulation.19
1. Motivation can be defined as the energizing of behavior in pursuit of a goal [Simpson EH, Balsam PD. The Behavioral Neuroscience of Motivation: An Overview of Concepts, Measures, and Translational Applications. Curr Top Behav Neurosci. 2016;27:1-12. doi:10.1007/7854_2015_402].
2. [Footnote#2 is mostly about the more specific neuroanatomy, intended for those with some knowledge of the subject. The terminology can be a little confusing. Footnotes 3-19 are (mostly) less neuroanatomically detailed and will be of greater interest to the general reader]. See here, here and here for simplified diagrams of some of the neuroanatomical regions and pathways.
The bottom-up circuits include the mesolimbic pathway (ventral tegmental area to nucleus accumbens) and mesocortical pathway (ventral tegmental area to prefrontal cortex). (Also: the bottom-up circuit involved in threat detection, not discussed here, includes the amygdala as a key component).
The top-down circuits involve the corticostriatal pathway. These run from the cortex, especially the prefrontal cortex (PFC), to the striatum. Neurons from the prefrontal cortex also project to multiple other regions.
The striatum is a composite structure consisting of the caudate and putamen (dorsal striatum), and nucleus accumbens (ventral striatum). The striatum is part of the basal ganglia and is involved in movement along with reward / motivation. Different regions of the striatum have been associated with different functions: the ventral striatum with reward; the caudate nucleus with cognition; and the putamen with motor control. However, corticostriatal connections are more complex, and interactions between functional territories are extensive [Haber SN. Corticostriatal circuitry. Dialogues Clin Neurosci. 2016;18(1):7-21. doi:10.31887/DCNS.2016.18.1/shaber].
The corticostriatal pathway provides most of the excitatory input into the striatum (mediated by the excitatory neurotransmitter glutamate).
Corticostriatal projections are essential components of forebrain circuits and are widely involved in motivated behavior. Many neurological and neuropsychiatric diseases involve dysfunction in the corticostriatal system. [Shepherd GM. Corticostriatal connectivity and its role in disease. Nat Rev Neurosci. 2013;14(4):278-291. doi:10.1038/nrn3469].
The circuitry linking the cortex and striatum is also important in mental disorders of control, such as attention deficit hyperactivity disorder (ADHD) [Maia TV, Frank MJ. From reinforcement learning models to psychiatric and neurological disorders. Nat Neurosci. 2011;14(2):154-162. doi:10.1038/nn.2723].
Note that the PFC is not "in charge" in some sort of independently executive manner. It is dependent on the input from lower regions—from the bottom-up processes (and it is biased by that input). The system essentially functions as a reciprocal stimulus-response loop.
3. Actually, there are three elements if we include learning processes (typically operating by Pavlovian or instrumental associations and cognitive representations). The top-down pathways from the prefrontal cortex play a key role in these learning processes.
[Click 'more' to view footnotes 4-19, below. The footnotes include more detail about how motivational circuitry works, more about ADHD, and further clarification of the free will question, among other topics]
4. Berridge KC. Food reward: brain substrates of wanting and liking. Neurosci Biobehav Rev. 1996;20(1):1-25. doi:10.1016/0149-7634(95)00033-b; Morten L. Kringelbach and Kent C. Berridge, "Neuroscience of Reward, Motivation, and Drive," in Recent Developments in Neuroscience Research on Human Motivation, ed. Sung-Il Kim, Johnmarshall Reeve, and Mimi Bong (Bingley, U.K.: Emerald Group Publishing, 2017).
5. “Wanting” processes involve a large and distributed brain system (including the mesolimbic and mesocortical pathways), whereas “liking” is served by a much smaller set of discrete hedonic regions in subcortical areas of the brain such as the nucleus accumbens and ventral pallidum (Kringelbach and Berridge). The nucleus accumbens, which can be thought of as the “Reward Anticipator,” evaluates stimuli that produce wanting or liking responses, and also plays an important role in learning from feedback and in reward based decision-making. See this interactive graphic of the brain circuits underlying motivation, provided by the Harvard Center on the Developing Child.
Other terms used with similar meanings to wanting and liking are incentive salience and hedonic impact, or appetitive and consummatory behaviors.
Most of our discussion on motivation and its circuitry has pertained to what is referred to as approach motivation—a propensity to move toward (or maintain contact with) a desired stimulus (i.e. seeking pleasure). There is also avoidance motivation—the propensity to move away from (or maintain distance from) an undesired stimulus (i.e. avoiding danger). [Feltman R., Elliot A.J. (2012) Approach and Avoidance Motivation. In: Seel N.M. (eds) Encyclopedia of the Sciences of Learning. Springer, Boston, MA. https://doi.org/10.1007/978-1-4419-1428-6_1749]. Desirable stimuli are referred to as having positive valence. Threatening or aversive stimuli are referred to as having negative valence. Hence there are positive valence systems and negative valence systems for detecting these. We are not focusing here on the negative valence system (avoidance motivation, i.e. avoiding danger). A key brain region in that system is the amygdala.
6. “Wanting” is mediated by dopamine, whereas “liking” involves endogenous opioids (as well as serotonin and endocannabinoids). Dopamine is not a “reward chemical” as such. It operates more as a reinforcer—it reinforces (and thereby orients) attention and motivation. It marks a stimulus as an important signal, against a background of “noise.” When dopamine gets activated in our brains by a particular stimulus or action, it is nature’s way of telling us that something is important for us—nature is telling us that we ought to focus on that stimulus or to persist in that action. Thus it selectively reinforces important learned information (or ideas) or important learned behaviors. More specifically, dopamine does this by encoding prediction errors, which are key to reinforcement learning. Prediction errors signal the difference between the observed and expected outcome: a positive prediction error signals that the outcome was better than expected, and a negative prediction error signals that the outcome was worse than expected. [Maia TV, Frank MJ. From reinforcement learning models to psychiatric and neurological disorders. Nat Neurosci. 2011;14(2):154-162. doi:10.1038/nn.2723]. When there is a discrepancy or error between expectations and perception (i.e., the perception of a stimulus or the outcome of a behavior does not match expectations), then dopamine release marks that event as important, novel and warranting attention (salient). If the perception exceeds expectations, it may then be experienced as rewarding and the person may seek to repeat the experience.
7. Executive function, self-control, self-regulation (SR), effortful control, and cognitive control are all related terms with overlapping definitions [Nigg JT. Annual Research Review: On the relations among self-regulation, self-control, executive functioning, effortful control, cognitive control, impulsivity, risk-taking, and inhibition for developmental psychopathology. J Child Psychol Psychiatry. 2017;58(4):361-383. doi:10.1111/jcpp.12675]. See also: Diamond A. Executive functions. Annu Rev Psychol. 2013;64:135-168. doi:10.1146/annurev-psych-113011-143750.
8. It's still more complicated than that, as people are not just defined by traits along a single dimension. For example, anxiety also motivates people, up to a point (beyond which it impairs motivation; that point differs between people). So an anxious person may be quite motivated even if they have weak executive function. Another example: it's possible to have weak executive function and yet be a perfectionist (which can be particularly frustrating).
9. Friedman NP, Miyake A, Young SE, DeFries JC, Corley RP, Hewitt JK. Individual differences in executive functions are almost entirely genetic in origin. J Exp Psychol Gen. 2008;137(2):201-225. doi:10.1037/0096-34220.127.116.11; Miyake A, Friedman NP. The Nature and Organization of Individual Differences in Executive Functions: Four General Conclusions. Curr Dir Psychol Sci. 2012;21(1):8-14. doi:10.1177/0963721411429458. See also: Rothbart M.K., Sheese B.E. and Posner M.I. Executive Attention and Effortful Control: Linking Temperament, Brain Networks, and Genes. Child Dev. Perspect. 2007;1: 2-7. doi.10.1111/j.1750-8606.2007.00002.x
10. Volkow ND, Wang GJ, Kollins SH, et al. Evaluating dopamine reward pathway in ADHD: clinical implications [published correction appears in JAMA. 2009 Oct 7;302(13):1420]. JAMA. 2009;302(10):1084-1091. doi:10.1001/jama.2009.1308; Volkow ND, Wang GJ, Newcorn JH, et al. Motivation deficit in ADHD is associated with dysfunction of the dopamine reward pathway. Mol Psychiatry. 2011;16(11):1147-1154. doi:10.1038/mp.2010.97.
11. Richard A. Friedman, "A Natural Fix for A.D.H.D.," New York Times, Oct. 31, 2014.
12. The most effective ADHD medications are stimulants (they’re in the same broad category as caffeine). Essentially, these medications increase the brain’s internal stimulation for a few hours, making it function more like the brain of someone who is more easily focused and more easily motivated by less stimulating, less rewarding tasks.
13. ADHD is thought to result from a primary deficit in inhibitory control, which causes deficits in executive function [Barkley RA. Behavioral inhibition, sustained attention, and executive functions: constructing a unifying theory of ADHD. Psychol Bull. 1997;121(1):65-94. doi:10.1037/0033-2909.121.1.65]. It also might result from excessive discounting of delayed rewards [Sagvolden T, Sergeant JA. Attention deficit/hyperactivity disorder--from brain dysfunctions to behaviour. Behav Brain Res. 1998;94(1):1-10)]. See also “Cost–Benefit Computation as the Arbiter of Motivated Behavior” in the Simpson and Balsam article cited in Footnote 1.
14. And of course, normal development has a profound effect on executive control and motivation, due to the incomplete development of brain regions that are involved in these processes (e.g. myelination of frontal lobe regions is not complete until the mid-20s). [Arain M, Haque M, Johal L, et al. Maturation of the adolescent brain. Neuropsychiatr Dis Treat. 2013;9:449-461. doi:10.2147/NDT.S39776].
15. On the other hand, in a state of hunger we’re of course single-mindedly highly motivated to obtain food.
16. The nucleus accumbens plays a central role in addictions.
17. Even if there is an element of randomness in some of the tiniest parts of the processes, this would still not confer true free will.
18. All the more so if we regard ADHD as simply one end of a normal continuum.
19. Free will is as much about choice as it is about motivation. All of our choices are at some level the product of all the antecedent events in our brain at the tiniest level, involving the astronomically complex interactions between our genes and environment over the course of our entire individual history, up to and including all the external circumstances shaping the present choice, and all the internal dispositional factors biasing that choice. Such an “equation” attempting to predict the choice the person will make would of course be inconceivably complex to compute—indeed, the “computer” required to do this calculation would practically have to be an exact copy of that person in the entirety of their environment, run over the time scale of their lifetime up to the moment of the choice about to be made. Furthermore, our genes are themselves the product of approximately 4 billion years of evolutionary history, which is itself the product of the physical environment on this planet, which in turn was the product of cosmological evolution. The “equation” predicting Mark’s, your or my choices is thus practically identical to the complexity of the universe itself, with all its contents including us. Given all this colossal complexity, we can for practical purposes regard ourselves as having “free” will.