The decisions we make range from those that occur in a split second to ones we delineate for days or even years. It feels natural to us—after all, we’re the ones making the decisions—but taking the time to stop and consider what really happens when we make a difficult choice is a fascinating thought experiment, one individuals have been pondering for millennia. The brain chemistry of how we make decisions is a multilayered process, but looking at the specific chemicals that play a major role can help give us an idea of what to expect.
One of these chemicals is dopamine, a neurotransmitter defined in casual speech as the unit of pleasure. It isn’t simply a measure of our pleasure, however: Dopamine is intricately tied with motor and motivational functions, and is vital “for the 'stamping-in' of stimulus–reward and response–reward associations” (Roy A Wise).
Figure 1: Dopamine and serotonin pathways exist throughout the brain, able to be transported in milliseconds. Dopamine is the primary neurotransmitter functioning to control motivation.
Source Credit: iflscience.com (LINK)
How does this vary for the different types of decisions we make, and what factors influence how much dopamine is released? Amount of time until reward is one, and actual benefit is another. For the former, an interesting phenomenon arises: the anticipation for a reward often realizes just as much dopamine as when the reward is obtained.
Researchers at Paris-Sud University have found that “For the first time, a direct link between DAT availability and reward anticipation was detected within the mesolimbic pathway in healthy and psychiatric participants, and suggests that dopaminergic dysfunction is a common mechanism underlying the alterations of reward processing observed in patients across diagnostic categories'' (Dubol et. al) - dopamine’s primary function serves as a method of anticipation.
The reward of anticipation is what motivates us to make decisions. But what changes between different decisions we make and the levels of dopamine released, as well as what factors create the most impact?
Besides the actual significance of the decision/reward, the amount of time until the reward arrives is key in determining how much dopamine is released and whether we commit to an action or not. Take the Stanford Marshmallow Experiment as an example of the dilemma: children could take a smaller reward without waiting (a single marshmallow), or receive a larger reward (a second marshmallow) if they were able to successfully wait 15 minutes. Clearly, a larger reward is necessary to justify extra waiting time, and, notably, the children that chose to wait had generally greater “success” in life. What allows us to wait and overcome instant gratification though is the ability of dopamine neurons to learn to encode the long-term value of multiple future rewards with distant rewards discounted.
Figure 2: A second trial of this experiment compared what happened when the marshmallow was exposed vs obscured, finding that the success of the experiment was more pronounced when the marshmallows were open to view while participants waited.
Source Credit: Simple Psychology (LINK)
That’s what happened in the Stanford Marshmallow Experiment, and why the children who could wait showed a correlation to higher SAT scores and improved BMI: the ability to assign long-term reward values for individual actions is a learned intelligence for the successful achievement of distant goals.
Time, practice, and learning all are factors that impact how our body uses dopamine to guide us to make our decisions. Understanding the science is important, then, as sometimes the short-term gains our brain wishes for do not align with the long term benefits we get from results that have delayed gratification. Dopamine holds the potential to understand that, and its lessons have far-reaching applications for our society.
Q&A:
Jiwon: In your article, you talk about how dopamine is produced in the process of anticipating a reward, and that time until reward is a factor that affects this dopamine production. How exactly, then, is the amount of dopamine affected by the time until reward?
Sadly, there isn’t a single answer to this question: it depends on the nature of the reward and the importance the brain places on the achievement. The brain’s expectations on how long it will take until a reward is earned is important, however: if the reward comes before, the brain treats it as a pleasant surprise, and dopamine levels increase. If no reward comes by the expected time, dopamines drops.
Sally: What about “How does this vary for the different types of decisions we make”?
Decisions that touch on more basic human needs–food, water, and sex, for example– would likely prioritize quick results, as more of the input into those decisions is placed by our amygdala. Decisions that involve more of the prefrontal cortex would likely be able to exhibit more long-term control. The expectations of our brain and subsequent dopamine release would likely reflect that.
Xavier: How can this information be applied to high school students’ everyday lives?
My personal takeaways from writing this article was the importance of training your brain to satisfy itself with long-term rewards: for the average high schooler, this could mean studying over playing around, sleeping over binge watching Netflix, etc. Knowing the workings of the brain on what seems to be an intuitive topic helps you be more aware as you make decisions in high school and beyond.
Wooseok: How can these studies on the capabilities/functions of dopamine be used to benefit humanity? (Like what are some possible ways in which this knowledge can be utilized?
E.g. development of drugs for specific disorders)
Dopamine truly reaches many applications, from resolving psychiatric disorders and drug addictions to optimizing our ability to make smart choices. One that I find most interesting is controlling dopamine release in the aftermath of opioid usage.
John: How does DA deficit affect such rewarding mechanisms?
Great question. Individuals with ADHD usually have lower levels of dopamine, which may explain why it’s hard for them to stay on one topic.
Works Cited:
Berke, J.D. What does dopamine mean?. Nat Neurosci 21, 787–793 (2018). https://doi.org/10.1038/s41593-018-0152-y
Decisions and Desire. 1 Aug. 2014, hbr.org/2006/01/decisions-and-desire.
Enomoto, Kazuki et al. “Dopamine neurons learn to encode the long-term value of multiple future rewards.” Proceedings of the National Academy of Sciences of the United States of America vol. 108,37 (2011): 15462-7. doi:10.1073/pnas.1014457108
Eshel, N., Tian, J., Bukwich, M. et al. Dopamine neurons share common response function for reward prediction error. Nat Neurosci 19, 479–486 (2016). https://doi.org/10.1038/nn.4239
Wise, R. Dopamine, learning and motivation. Nat Rev Neurosci 5, 483–494 (2004). https://doi.org/10.1038/nrn1406
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