You don’t need to look far to find alarming stories about Americans’ unhealthy behaviors. Such stories commonly mention poor diets, insufficient physical activity, excess alcohol drinking, smoking and street drugs. These unhealthy behaviors predict rising prevalence of major chronic conditions, such as type 2 diabetes, obesity, and kidney disease. Most deaths in developed countries now arise from chronic diseases that are largely caused by unhealthy behaviors.
The evolutionary basis
Many of us seem to regard our fellow Americans who have these medical conditions as deserving their fate due to a shortage of will-power or character defects or moral failure. A recent book by a professor of behavioral and social sciences at Brown University paints a different picture. In Darwinian Hedonism and the Epidemic of Unhealthy Behaviors, David Williams makes the case the lack of will-power, character defects, and moral failure are not the main culprits. Williams argues that humans are evolutionarily predisposed to eat sweet, fatty, caloric-rich foods because we are hedonically motivated to do so. Furthermore, he says that we are also evolutionarily predisposed to avoid unnecessary energy expenditure (that is, physical activity).
Theory of hedonic motivation
Psychological hedonism refers to the human tendency to pursue behaviors that previously resulted in pleasure and to avoid behaviors that previously resulted in displeasure. Williams reconceived psychological hedonism as Darwinian Hedonism to emphasize its evolutionary roots. In particular, human evolution favored those who preferentially ate calorie-dense, sweet and fatty foods, because these people were more likely to live and pass on their genes to the next generation. Similarly, humans who avoided unnecessary energy expenditure also preferentially passed their genes to the next generation. Thus, modern humans have a genetic predisposition to like calorie-dense, sweet, fatty foods and to dislike unnecessary physical activity.
The main feature of Williams’ book is hedonic motivation, which is the automatic desire or dread based on previous pleasure or displeasure in response to a stimulus. Hedonic motivation is usually the immediate cause of behavior. I’ll use the nonfictional character, Alan, and his love of donuts to illustrate hedonic motivation. When Alan encounters a donut-related stimulus (such as driving past a donut shop on his way a field visit), he experiences a liking for a donut. Since Alan leaves home early and has time for a stop, he stops and walks inside the donut shop. The smell of the freshly made donuts subconsciously reminds him of pleasurable past experiences he’s had eating donuts while driving to other field sites. Alan’s likely genetic predisposition for sweets and fats and his pleasurable prior experiences lead him to experience hedonic motivation. Environmental cues (such as the smell of food and seeing other customers enjoying their donuts and coffee) and the physiological drive of hunger heighten Alan’s hedonic motivation. All of the foregoing lead to behavior (Alan buys a donut and coffee and takes a bite of donut before leaving the shop) that creates a hedonic response (yum!).
There’s more to the story. Alan knows that donuts are unhealthy – sugar, fat, white flour. In this instance Alan rationalizes that one donut won’t do him much harm. Plus, he knows that he’ll be doing physical work on the job site and will burn off the donut’s calories. Sometimes Alan drives post the donut shop and doesn’t stop. On these occasions, reflective motivation (see below) overrides hedonic motivation.
Neurological basis
Hedonic motivation has a neurological basis that evolved over eons of time. Wanting represents the neurological basis of hedonic motivation. Wanting links to the production of dopamine in the hypothalamus and the nucleus accumbens, among other brain regions. Liking represents the neurological basis of hedonic responses. It links to the production of opioids in the nucleus accumbens. Alan wants a donut (hedonic motivation). Upon eating the donut, Alan experiences a liking for the donut (hedonic response). Over time, repetition of this series of events solidifies in Alan’s mind the pleasurable association of liking donuts, which induces the hedonic motivation to want a donut the next time he drives past the donut shop.
Diet
Modern ultra-processed foods closely match our genetically predisposition for calorie-rich, sweet, and fatty foods that was adaptive eons ago but is not adaptive now. The food industry has spent vast sums of money designing foods that have precise combinations of sugar, fat, salt, and flavorings plus desirable mouth feel as to be essentially irresistible. We modern humans are hedonically motivated to overeat and to eat junk food.
Physical activity
The current epidemic of physical inactivity due in part to evolutionarily developed genetic disposition for and hedonic motivation to conserve energy that was adaptive a million years ago for proto-humans. For most people, the act of exercise feels unpleasant; being done with exercise can feel good but not the exercise itself. Humans are instinctively motivated to avoid unnecessary physical activity, even if the associated physical activity doesn’t feel bad. Even for people with little dread of physical activity, it competes with pleasurable sedentary activities such as watching TV, surfing the web, checking messages, listening to podcasts, reading, and taking the elevator at work.
Motivational mismatch
Our hedonic motivation is mismatched with our modern, obesogenic environment that feature widely available and intensely promoted irresistible, calorie-dense, irresistible foods laced with sugar, fat, salt, and flavors. Can you eat just one Lay’s potato chip? The hedonic motivation for sweet, fatty, and salty foods that was adaptive hundreds of thousands of years ago is not adaptive now. We eat too much food, especially calorie-dense food, because we’re hedonically motivated to do so. We avoid physical activity because we’re hedonically motivated to do so, as well. Labor-saving devices allow most people, especially seniors, to get along in their daily lives with minimal physical activity.
Reflective motivation
As noted above, Alan doesn’t always eat a donut when he drive past the donut shop. Why not? Sometimes Alan experiences reflective motivation, which is the thoughtful consideration of the likely consequences of one’s behavior.
Reflective motivation is similar to dual-processing theory, which was popularized by Nobel laureate Daniel Kahneman is his book Thinking Fast and Slow. Fast thinking tends to be automatic, done without conscious thought, and evolutionarily ancient. It’s not surprising that we typically don’t have reasons for hedonic motivation or we aren’t aware of the reasons. Fast thinking is highly useful for many activities such as driving a car. Most of the time we can respond quickly and effectively to changing conditions without having to think much if at all. Fast thinking fits with hedonic motivation and the behavior of eating a bag of chips while lounging in front of the TV
Slow thinking tends to controlled and requires mental effort. Slow thinking is more useful is situations when consideration of multiple points of view will lead to better results. Slow thinking promotes reflective motivation as an alternative to hedonic motivation. Reflective motivation aligns with slow thinking.
Most of the time when Alan drives past the donut shop, he uses fast thinking (if he’s thinking at all) and simply responds to his hedonic motivation of wanting a donut. At other times, he considers his expanding waistline, which he doesn’t want, and keeps on driving.
Hedonic motivation vs. reflective motivation
Life doesn’t occur in a vacuum. Context cues influence both hedonic and reflective motivation and their relative strengths. Environmental factors, such as the sight of a donut shop, the smell of food, and the proximity of the donut shop can trigger hedonic motivation. Situations that require mental effort diminish reflective motivation in favor of hedonic motivation. Hedonic motivation will likely prevail over reflective motivation when we are not paying attention or if we are tired or hungry or out of sorts.
As noted above, hedonic motivation can sometimes be countered with reflective motivation. Reflective motivation is more likely to prevail when we're paying attention to what we're doing or don’t need to make a quick decision or when we can step back (sometimes literally) and ponder our goals and intentions.
Where do we go from here?
Scientists design interventions to promote better diets and more physical activity. These direct interventions are usually aimed at individuals or of groups of people. Such interventions generally feature aspects of social cognitive theory abetted by environmental components. For example, interventions commonly seek to build self-efficacy, help participants set goals and intentions for healthy behaviors, identify barriers to health behaviors, track progress toward goals, and provide social support. Social cognitive interventions may be effective in promoting healthy behaviors, but improvements tend to diminish after the intervention stops (and hedonic motivation reasserts itself).
Williams proposes a public health approach to stem the tide of unhealthy behaviors. The best approach requires policies that make the cues for hedonic motivation disappear or make them less attractive. Some possible ideas: 1) prohibit junk food in school lunches, 2) impose taxes on sugary drinks, 3) ban junk food advertising to children, 4) provide incentives for healthy behaviors such as free or low-cost gym memberships, 5) place graphic images of damaged lungs, blood vessels, brains on packages of ultra-processed foods that become mentally linked to these unhealthy conditions, 6) develop public service messages (paid for by taxes on sugary drinks) that link unhealthy behaviors to bad outcomes in order to reduce hedonic desire. Alas, the political will to enact policies to obscure the cues for hedonic motivation will require an informed and aroused public so as to overcome self-serving arguments from the food industry, among others.
Williams offers this perspective: “Hedonic motivation is automatically triggered by our desires and dreads, not by the reasonableness or nobility of those desires and dreads. From a scientific perspective, we must work to understand the hedonic motivations for unhealthy behavior, not judge them as morally right or wrong.”
