Neurobiology for optimal game UX
Playing a well-made video game can make us feel satisfied or even happy. Is there an answer to what causes that feeling and makes games so successful, helping big game corporations earn millions of dollars? Is it an interesting narrative or a good balance and a smart monetisation model? Likely you can come up with many possible combinations and the answer will be correct, but it is important to understand why.
No matter what makes you feel good, the feeling of satisfaction and happiness is caused by the chemistry of the brain. In this article I will review the following topics:
- Why evolution made us love to play
- The basics of neurobiology to understand how the brain works while we play
- Biological purpose of hormones that provide happiness and pleasure
- Review the dopamine craving circuit and the basics of addiction
- Examination of some popular game mechanics and techniques
Understanding how it works on molecular level might help game experience designers to look at the process of experiencing fun while playing games from another angle where questions like “why some mechanics work better than another”, “why the given reward will never be enough”, “why we always feel unhappy when there is a lack of new information” are easily explained.
Origins of play
Play is older than culture, for culture, however inadequately defined, always presupposes human society, and animals have not waited for man to teach them their playing (Huizinga 1955).
If we take a look at the animal kingdom we will notice that even species with relatively simple organization, such insects and octopuses, are playing. Various studies have shown it mainly happens to serve a special biological purpose:
- Practice theory — borrow actions from aggressive, hunting or sexual behaviors thus preparing for adulthood.
- Social bonding — stay together with whom you’re playing.
A study by Nunes  showed that squirrels who played more are better coordinated, but more importantly, these extra playful individuals were more successful in their first breeding season. Another study  about rats (which behave as primates, including humans) proposed that play might help to read the intentions of others and boost their confidence by letting them experience winning and losing in a non-threatening way. Furthermore, rats raised with lots of companions developed heavier cerebral cortexes with more neural connections and could learn faster, than rats that grew in ascetic environment.
On the other hand, there are also dozens of researches showing that mammals get no special benefit from play. For instance Lynda Sharpe earned her PhD trying to discover why meerkats play. Cats, mice, meerkats, coyotes and some other mammals play without getting better at hunting, breeding, etc. If we assume that play sometimes doesn’t have a function and happens just without a reason, there is one problem: it is energy expensive and can even be risky. Therefore, besides all the inconvenience, a good session of play is always followed by fun and satisfaction. Unnecessary to say, these two components are essentials for any of humans’ play. Nowadays we do not need to think a lot about our survival needs and skills, we merely flow through our daily routine. We are eager to find anything that can stimulate us to experience happiness or pleasure and reduce the pervasive malaise and anxiety. Food, water and sex are the first vital components that bring us satisfaction, give us a feeling of reward which is mostly induced by the dopamine-craving circuit.
This circuit was made by nature to accomplish only one goal — to keep our DNA alive. It based on a simple heuristic — “what is good for you should be encouraged, so you can seek it out again”. In the animal world, the stronger the mechanism works, the better. There is nothing artificial that animals can wrongfully perceive to get a dopamine release from the circuit. It has been polished by thousands years of evolution filtering what is good and bad.
When in 1954 James Olds and Peter Milner discovered a phenomenon called “brain stimulation reward”, it demonstrated that stimulation of dopamine release was more important than food and water. The scientists inserted an electrode straight into the reward center of a rat’s brain and gave it an opportunity to trigger the lever which activated the electrode. The rat pressed the lever so often that it eventually died, ignoring all other vital stimulus. But why did the brain evaluate the pleasure from dopamine so high and let the animal die, instead of stopping the process to eat, drink and breed? The answer is because active release of dopamine is stimulated by anticipation of reward. The rat kept anticipating from each push a new reward, because it released much more dopamine than she could get from a really important stimulus. In its turn, humans have found a lot of different ways to stimulate release of “pleasant hormones”. We voluntarily put ourselves in place of that rat with electrodes in the brain via use of drugs that directly affect the brain chemistry, we play video games that use evolution mechanisms to make your brain encourage you.
Feeling of happiness
No matter how we get a feeling of happiness, it is always controlled by special hormones: dopamine, endorphin, oxytocin and serotonin, which are released when our brain notices something good for our survival. On the other hand cortisol, adrenaline and norepinephrine are three major stress hormones. Each of these chemicals triggers a different emotion and its surge is controlled by special parts of the brain: limbic system, basal ganglia, ventral tegmental area (VTA) and prefrontal cortex.
The limbic system structures (hippocampus, amygdala, thalamus and hypothalamus) are involved in forming our emotions and motivations. This includes fear, anger, emotions related to sexual behavior and also feelings of pleasure related to our survival like experience from eating and sex. Additionally, the limbic system is responsible for memory formation, integration, olfaction and mechanisms to keep ourselves safe.
Each of the hormones was made to regulate special functions and is involved in different circuits. I will describe only the most important behavioral actions and motivations to help understand the nature of happiness and satisfaction
These hormones do not flow constantly. The brain motivates us to search for better resources and improve the quality of life by letting us crave for a bigger portion of hormones to get a feeling of happiness again, or by forcing us to avoid unpleasant feelings triggered by cortisol. However, we all have unique ways to turn on the release of those hormones, because we build neural pathways from our unique life experience. The electricity in the brain flows through the path of least resistance and does not flow easily along the neurons we have never activated before. Our brain evolved to store experience, not to remove it. That is why sometimes we like things which can be not good for us or we can feel the anxiety while experiencing something harmless.
Below are two examples when that evolutionary mechanism can give us negative consequences:
- A popular episode in psychiatry: a girl who suffered in a car accident started to get panic attacks when she heard a laugh. With a psychiatric help she found out that before the accident she was in the car, joking and laughing with her friends. Her brain made a connection between laugh and an immediate strong pain after it. Of course consciously she understood that laugh was not a cause of the accident, but cortisol paths were activated before the cortex could filter the information and alerted her about “coming pain” forced her to do something. As a result she experienced a great fear.
- A common domestic case: a girl has been experienced a break up with her boyfriend, she is in a bad mood, but buys and eats a chocolate cake by that triggering her level of dopamine to go up. Survival-enhancing sugar is the easiest way to get energy and was always encouraged by evolution. In this case her reward circuit is activated, hippocampus starts to store the memory about an “easy way to get a reward”. The next time she feels anxious or a little bit sad, her brain will give her a clue what to do. That is why some people end up with weight gain problems after being stressed.
The mechanism is strong, and as Schopenhauer noted in his book “The World as Will and Representation” make our existence like a wheel of desire. We want, we satisfy our desire, for some time we feel pleasure, which very fast grows into boredom, that in its turn soon is replaced with a new desire. Every release of dopamine ends and it’s possible to get more only when your brain sees another chance to achieve a better reward. Dopamine will be released only when we find something more relevant to survival instead of wasting energy on easily available things. If it is easy to get a reward very soon it will not bring any excitement.
The fleetingness of dopamine was illuminated by a famous study by W.Shultz  where monkeys were trained to get a spinach as a reward, that produced small dopamine spikes. Then the reward was replaced with tasty juice, perceived as a better sugar-rich reward. After few days a curious thing happened — there were no dopamine spike in response to getting juice. The brain stopped reacting to rewards that just came on their own and took it for granted. In other words, when there is no new information, there is no need of dopamine. Besides, the experiment had a dramatic final when the reward was switched back to spinach and the monkeys reacted with fits of rage. They had learned to get juice and even though it didn’t make them happy, losing it made them mad.
It is important to remember that it is challenging to stop release of cortisol, because our brain was made to defend us from different threats. Our ancestors went through hunger and cold, defeated predators only because cortisol made them feel bad until they found the way to stop it from being released. However, when we have satisfied our physical needs, our attention switches to the social threats.
Sometimes switching attention to a different activity helps us to deal with cortisol, that eventually makes us form different habits like drinking alcohol and gambling or exercising and meditating. We make a choice ourselves and brain helps us to memorise it as a way of avoiding cortisol trigger. Playing video games that help to relax and switch attention from the real world could become such habit as well.
Video games and neurotransmitters
Unlike animals, in addition to playing humans have invented games. The biological basis for existence of a game entity is the same as for a play that was described before — to get a portion of “happy hormone” reward or as a way to avoid cortisol triggers. Distinctions between both are highlighted in definitions:
- Play is an open-ended activity in which make-believe and world-building are crucial factors as defined by .
- Game is a system in which players engage in an artificial conflict, defined by rules, that results in a quantifiable outcome . In a game a player makes choices to overcome challenges which can change the state of the game and with certain amount of chance make it unpredictable to find a perfect choice to win .
The game world is usually a contrast to our reality and provides full spectrum of desirable hormones.
Dopamine is released after meeting the game goals, finding what you seek, stretching body and mind to its limits. Examples from games:
- Acquisition of new skills / abilities / items
- Accomplishment of new levels / quests
- Discovery and exploration of new areas
- Winning a competition
- Getting a reward box to open
- Longer quest stimulates longer surge
Serotonin is released with experience of comfort, dominance in the social group. Historically, it has been connected with an easy access to food resources, which inside a group usually depended on a high social status. In game context it is released in following situations:
- Social interactions
- The pride of associating with a certain stature (guilds / groups)
- The feeling of being “right”
- Respect from others
Oxytocin is released with feeling of belonging and safety, because from evolution point social trust improves survival prospects. Situations in gaming context are:
- Social trust (feeling supportive)
- Social bonds
- Feeling bonded to be in the same situation with others
Cortisol is released every time the brain realises we are encountering survival threats. A big burst of cortisol we call “fear”, a small one — “anxiety or stress”. In the context of gaming we experience it in the following situations:
- Technical issues
- Difficult interface comprehension
- All scary situations (Adrenaline might partially compensate bad experience)
- Gacha (big anticipation against low level reward)
- Social conflicts
- Waiting (anticipation of immediate feedback is ruined)
- Overly hard-to-achieve goals
- Status maintenance and etc.
To understand how video games affect our brain we need to look at a process called neurotransmission or synaptic transmission, which is fundamental to how the brain works. Our brain mostly consists of cells called neurons and glial cells. Neurons have:
- A cell body as all cells do,
- Dendrites — the branched projections of a neuron which are used to collect signals coming from other cells,
- An axon — a long projection of a neuron cell that conducts electrical impulses to other neurons.
At the end of an axon is a synaptic or axon terminal, that makes very close apposition with the next neuron’s dendrite or another cell. Inside the axon terminal are small vesicles that contain special substances called neurotransmitters, for example dopamine, serotonin and oxytocin.
The way the neurotransmission works is that a nerve impulse called “action potential” caused by ions (charged molecules) starts in the cell body and propagates down the axon.
When impulse reaches the axon terminal it triggers the release of neurotransmitters from the presynaptic cell. They cross the synapse (the gap between two cells) and bind to membrane receptors (specific proteins) on the postsynaptic cell conveying an excitatory or inhibitory signal, so the next cell can be activated. The process can go on along the chain containing many nerve cells. This is how circuits or pathways maintain communication and eventually to produce some function.
When it comes to understanding how we get happiness from playing games or understanding the game addiction, the synapse is the most important part.
The image above shows a nerve terminal containing storage vesicles with dopamine inside. There are receptors on the postsynaptic cell. When a nerve impulse invades this nerve terminal, the vesicles fuse with the membrane and secrete the neurotransmitters into the synaptic space where they diffuse and bind with receptors. The neurotransmitter-receptor combination is what produces the signal in this postsynaptic cell. The signal has to be discrete, that means eventually stopped. In other words, the neurotransmitter has to be removed from the synaptic cleft.
Neurotransmission is a quick on-off process and in case with dopamine the molecules, that have not bound with the receptors, are going back to the presynaptic cell with the reuptake pump. The uptake also restricts the spread of dopamine.
There are neighboring neurons that also take part in neurotransmission releasing compounds called a neuromodulators. They are substances which have little or no effect on their own but can enhance or inhibit the action of neurotransmitters. Endorphins are neuromodulators in dopamine transmissions.
Games and dopamine craving circuit
Now let’s look at an example of the dopamine craving circuit activation while playing a game:
A player completes quests killing different enemies to get a powerful weapon. Then he uses it to fight the final enemy and unlocks a new ability. The player reaches his goal and explores something new. The brain perceives it as something very important — our ancestors would have experienced it when discovering new plants to harvest, new water source or even a new partner.
Reaching goals and exploring are actions that evolution has taught us to encourage by sending an electrical impulse through a dopaminergic neuron. Dopaminergic neurons are predominant components of ventral tegmental area (VTA), accounting to around 60%. The dopamine released from VTA propagates to many different parts of the brain:
- Amygdala is responsible for memory, decision-making and emotional reactions. Right amygdala induces negative emotions like fear and sadness. Left amygdala is able to induce both pleasant emotions like happiness and unpleasant like fear, anxiety, sadness. In the example with the player it induced positive emotions because the player finally got a desirable ability.
- Nucleus accumbens is involved in the encoding of new motor programs. It helps players to memorize fast mouse clicks, successful combinations of the hotkeys, etc.
- Prefrontal cortex is involved in planning complex cognitive behavior, personality expression, decision making and moderating social behavior. It helps player to stay focused on the game and not divert his attention.
- Hippocampus is responsible for the formation of memories that helps to remember what causes good feelings. The player remembers what he accomplished, how he killed enemies, how fast he had to react, if he used a PC or console, if he was sitting in a internet cafe or at home and so on.
This dopamine-reward circuit is intended to make us remember ways of getting good emotions, force you to repeat and reinforce.
Before the player reached his final goal of unlocking a new ability he had completed a list of small tasks like killing a lot of enemies. Before he learned how to do it, he had to learn many things, for example — how to run, how to use the weapon, how to use the ultimate ability. With the help of basal ganglia he has formed a special chunk of actions which led to activation of the reward circuit. The player has formed a habit of killing enemies without thinking about how he is doing it — what we, in gaming terms, call “grinding”.
Our brain always tries to save resources, that is why everything that is easily accessible will not provide a lot of reward. That is why eventually “grinding” is perceived as something boring.
Chunks of action and game addiction
The ability to form such chunks of actions is necessary in our everyday life. Repeating a sequence of actions A1+A2+A3 to get a special outcome will eventually form a chunk, which our brain will remember how to do without processing each action separately. These are “autopilot actions” or “habits” that make us do things much faster because making a deliberate action always requires time. After dozens of repetitions we do not think how to tie our shoelaces, though in the beginning it required all our attention and was pretty slow. If we mistype a word, for many of us it is easier to retype it than go to the middle of the word and fix that concrete mistake. However, chunking has its own disadvantage, once the chunk has started it will go through the whole sequence and will happen regardless of the outcome. In a few words:
- Chunks or habits are fast but inflexible
- Deliberate actions are slow but flexible
Addiction is based on this mechanism. Habits do not even need a positive reward to be done. In the following I illustrate two different situations showing how game addiction may be formed in one of them:
- A player returns to a game once in a week and gets his portion of dopamine. He plays infrequently and his dopamine level has time to go back to normal. He enjoys the game from time to time and feels nothing but a satisfaction.
- A player returns to a game more than 1–2 times a day. He gets his dopamine reward the first time and is very excited. He is ready to repeat again and get more because it was good before. This person has enough time to do it again many times. Dopamine is released again as well. But what if after the player has completed an easy task he choses a difficult one? He almost gets a reward, but fails, however, his dopamine level increases, because he was close to get what he wanted and anticipation caused a dopamine surge. Completing the difficult task will only make the circuit stronger because the reward for it is bigger and better. This is how games become so desirable and sometimes even addicting to us. Immediate feedback, formed chunks of actions, full stack of “happy hormones” get players hooked.
Each of game mechanics can be explained from the neurobiological point of view. It becomes easier to see and emphasize the element that makes a mechanic successful or to explain why it does not work well.
Once we know how dopamine circuit works, it becomes easy to understand why endless collecting might be one of the best game mechanics and still a popular hobby. The first benefit of collecting — it is not directly connected to cortisol surges unless you are involved in some conflicts or challenges. It helps you to get over disappointment — a collector is always in a search. When he finds what he seeks, the dopamine level goes down and a new search starts. It creates an illusion of different needs that have to be satisfied. Besides, during collecting the brain process a lot of new information and as a result is less affected by stress hormones. If a collector is more successful than his colleagues-collectors, he also gets a portion of serotonin. The only one requirement to continue that pleasant condition — a person has to keep searching.
Invisible simulation of stretching the limits
M. Csikszentmihalyi in his book “Flow” said: “The best moments usually occur when a person’s body or mind is stretched to its limits in a voluntary effort accomplish something difficult or worthwhile.”  This is not surprising since stretching the limits has all the prerequisites for a good dopamine portion: attaining what you seek and something new you have never experienced before. Finding a way to make players feel like they stretch their limits even if they do not can be very beneficial for both developers and players. It is a relatively cheap way to add some moments of awesomeness to a game, but it should not be obvious at least to an average player. Of course it is not trivial and, but many companies use this trick to make experience better.
In Bioshock if you would have taken your last pt of damage you instead were invulnerable for about 1–2 sec so you get more “barely survived” moments.
— Paul Hellquist (@TheElfquist) September 1, 2017
Assassin’s Creed and Doom value the last bit of health as more hit points than the rest of it to encourage a feeling of *JUST* surviving.
— Jennifer Scheurle (@Gaohmee) September 1, 2017
Many games have competition as the main feature. The player has to stretch his skills to meet the challenge provided by the skills of the opponent. The roots of the word “compete” are the Latin con petire, which means “to seek together”. Each person seeks a way to actualize his potential and it becomes easier when someone else forces us to do our best. It is important to remember that competition can become a distraction if the extrinsic goals like impressing an audience, beating an opponent are what a person is concerned about.
Aleatory games are enjoyable because they give us an illusion of controlling the future. The experiments by Cambridge neuroscientist W.Shultz  gives an explanation why. He followed a simple protocol: he sounded a loud tone, waited for a few seconds and then squirted some drops of juice into the monkey’s mouth. While the experiment was unfolding he monitored the neurons’ activity. At first the dopamine neurons fired only when the juice was delivered, it was a response to the actual reward. However, after few trials monkey learned that the tone happens before the arrival of juice and the same neurons began firing at the sound of the tone instead of the juice reward. Shultz called these cells “prediction neurons”, since they were more concerned in predicting rewards than actually receiving them.
However, if the cellular predictions proved correct and the rewards arrived right on time, then the primate experienced a brief surge of dopamine, the pleasure of being right. However, if the pattern was violated by not supplying juice after the tone, then dopamine neurons decreased their firing rate. This is known as a prediction-error signal. The monkey felt upset because its prediction of juice was wrong. The brain is designed to amplify the shock of these mistaken predictions.
Social engagement and mirror neurons
Another thing that helps to maintain a strong desire to continue playing is mirror neurons. Activation of mirror neurons makes social connections easier and happens when you see someone you care about being rewarded or in danger. That induces a release of same hormones as for the other person, but in lower amount. If other players around you celebrate their goals and experience joy, you would likely desire to experience the same feelings.
When something goes wrong
It is not a fresh idea to use neurobiology and psychology in designing better game user experience, but it is still possible to avoid some design mistakes using a deeper understanding of how our brain works. Sometimes developers chasing an objective of giving “the best experience”, try to raise more dopamine by giving an extremely appealing content, but face the trouble of getting the opposite effect. Loot box designs are a good example how dopamine can spoil the efforts your team puts into development of high-quality animations and items. When creating a jaw-dropping animation seems to be a logical and the only way to go, it is important to remember that big anticipation needs a big reward. If in Overwatch it is justified, then The Division presents an unsuccessful approach where a complex ceremony leads to a disappointing reveal of icons for bottom-of-the-barrel goodwill finds and gun skins. Even experiencing it again, the brain will still expect a relevant reward. It is important to remember — cheating will not work with the brain as it has been trained for thousands of years of evolution.
Many video games offer a highly effective reward schedule. The feedback they provide is very fast, the pleasurable moments are brief, but they have a rapid onset and are repeated often.
Most good games are not only highly addictive, they also require a variety of cognitive and motoric capabilities, and can be seen as an intense training of skills relating to these. For example, platformer games stimulate growth of gray matter in brain areas crucial for spatial navigation, strategic planning, working memory and motor performance. Playing platformer games can reduce the incidence of certain diseases, by counteracting risk factors such as diminished prefrontal cortex volume which is associated with PTSD and schizophrenia . On the other hand, there are dozens of people who have died because of game addiction, trying to make themselves happy by exploiting their dopamine circuit, but neglecting essential physiological needs. We have to remember that our brain does not differentiate between the dopamine reward released from sex, computer games or drugs.
We want to get pleasure and satisfaction from our lives, and this drive keeps us evolving and helped us survive for hundreds of thousands of years. All living organisms struggle to satisfy their daily vital needs. Fortunately, most humans do not spend much time finding food and keeping themselves safe. However, evolutionary mechanisms change slowly, that is why we still want to get more pleasure from our lives even when it seems every need is fulfilled. We can not ignore this craving from our lives and strive to find joy and the meaning of life, that in itself is a long term goal that brings us the greatest satisfaction. To fill our lives with new experiences every day, we need to be inventive and have enough resources. Unfortunately, sometimes we choose to activate our dopamine neurons in ways that can lead to addiction. In the list of things that can help us get a quick portion of happy hormones, video games look pretty compelling, especially if we consider elements of training and learning. As developers we should aim to make our games pleasant and satisfying, rewarding players wisely, making them feel good from time-to-time without abusing their nature-given reward circuits.
Hormones perform a broader list of functions than I have described and this was just a brief overview of what we are dealing with when we design game features. It is absolutely possible to design a great game without knowing these underlying mechanisms, simply by following common practice and relying on predictable results. But even though some experiences will generate the same results for large audiences, there will always be individuals who experience things differently. The neural pathways of the individual are shaped by their unique life experience.
 Nunes, S., Muecke, E-M., Lancaster, L.T., Miller, N.A., Mueller, N.A., Muelhaus, J. & Castro, L. 2004. Functions and consequences of play behaviour in juvenile Belding’s ground squirrels. Animal Behaviour
 Ferchmin, P. A. & Eterovic, V. A. Play stimulated by environmental complexity alters the brain and improves learning abilities in rodents, primates and possibly humans. Behavioral and Brain Sciences
 Rules of play Katie Salen & Eric Zimmerman 2003, p.96
 Flow: The Psychology of Optimal Experience Mihaly Csikszentmihalyi
 How We Decide by Jonah Lehrer
 Nolte’s The Human Brain 7th Edition
 Richard M. Ryan · C. Scott Rigby · Andrew Przybylski The Motivational Pull of Video Games: A Self-Determination Theory Approach Pdf
 Playing Super Mario induces structural brain plasticity: gray matter changes resulting from training with a commercial video game 2014 link
 S. Smith Playing action video games may be bad for your brain, study finds 2017 link
 Nauert PhD, R. (2015). Video Game Lowers Stress Hormone link
 Sociable Killers: Understanding Social Relationships in an Online First-Person Shooter Game Pdf
 Impact of videogame playing on glucose metabolism in children with type 1 diabetes link
 Bo Kampmann Walther Playing and Gaming. Reflections and Classifications link
 D.W. Pfaff Hormones, brain and behavior 3d edition