Sadness from heartache, elation at finding a long-lost friend, anxiety before a job interview -- you might like to think you're completely in control of what you feel and that you understand what causes those feelings. But your brain can be sneaky sometimes.
A lot is going on inside your head, and your brain and its complex processes are even manipulating your emotions. In other words, there's way more behind that angry feeling than the car that just cut you off. Much is involved in interpreting emotional circumstances and crafting your responses to them, and your brain is affecting how you feel and how you respond to those feelings in ways you're probably not even aware of. This leads us to ask: What's going on up there, and just how is your brain influencing your emotions? Keep reading to find out.
Even though we think of emotions as internal states, psychologists define emotions as a combination of cognitions, feelings and actions [source: Kalat]. This means what we think of as "emotions" includes not only how we feel, but also how we process and respond to those feelings.
To understand this, it's helpful to consider the purpose of emotions. In 1872, Charles Darwin first published "The Expression of the Emotions in Man and Animals," which established that emotions serve an important evolutionary purpose. In order for a species to continue, it needs to survive and pass on its genetic information. Emotions like fear serve to protect you from danger so you can survive to pass on your genes. The "fight-or-flight" response that primes your body to defend itself or run away from danger is also an emotional reaction. Emotions like love and lust give you the desire to reproduce.
For these reasons, the brain takes on the function of evaluating a stimulus -- such as a dog that's about to attack or a beautiful woman batting her eyelashes -- and crafting an emotional response to it. The brain thinks in terms of how it can best respond to a situation in order to survive and reproduce, and it uses emotions as the catalyst to convince the rest of your body to act accordingly.
Your brain is a complex network that processes vast quantities of information every second. Part of the brain's information-processing network includes neurons, or cells that transmit signals throughout the brain. Neurons send signals through neurotransmitters, which are chemicals some release and others receive. These chemicals essentially let the parts of the brain communicate with each other.
The three most commonly studied neurotransmitters are dopamine, serotonin and norepinephrine. Dopamine is related to experiences of pleasure and the reward-learning process. In other words, when you do something good, you're rewarded with dopamine and gain a pleasurable, happy feeling. This teaches your brain to want to do it again and again. Serotonin is a neurotransmitter associated with memory and learning. Researchers believe it plays a part in the regeneration of brain cells, which has been linked to easing depression. An imbalance in serotonin levels results in an increase in anger, anxiety, depression and panic [source: Nazario]. Norepinephrine helps moderate your mood by controlling stress and anxiety.
Abnormalities in how the brain receives and processes these chemicals can have a big effect on your emotions. For example, when you do something rewarding or pleasurable, the part of your brain that processes that information interacts with the chemical dopamine. If your brain can't receive dopamine normally, the result is that you feel less happy -- or even sad -- after what should have been a happy experience. Studies of people with major depressive disorder (MDD) have shown that they have fewer serotonin receptors in their brains [source: National Institutes of Mental Health].
Your brain is made up of many different parts that all work together to process the information it receives. The main part of the brain responsible for processing emotions, the limbic system, is sometimes called the "emotional brain" [source: Brodal].
Part of the limbic system, called the amygdala, assesses the emotional value of stimuli. It's the main part of the brain associated with fear reactions -- including the "fight or flight" response. A person who has a seizure in the temporal lobe (the location of the amygdala) sometimes reports an intense feeling of fear or danger [source: Fiori].
The part of the brain stretching from the ventral tegmental area in the middle of the brain to the nucleus accumbens at the front of the brain, for example, has a huge concentration of dopamine receptors that make you feel pleasure [source: Banich]. The hypothalamus is in charge of regulating how you respond to emotions. When excitement or fear causes your heart to beat faster, your blood pressure to rise and your breathing to quicken, it's the hypothalamus doing its job. The hippocampus turns your short-term memory into long-term memory and also helps you retrieve stored memory [source: BBC]. Your memories inform how you respond to the world around you, including what your emotional responses are.
Because different parts of the brain process different emotions in different ways, injury to any part of the brain can potentially change your moods and emotions.
If you were to crack open your skull and take a look at the gray matter contained within it, you'd see that the brain appears to be divided into two equal-sized halves. These are your brain's hemispheres and, while they work together to keep you functioning, they each take responsibility for processing different types of information. The left side of your brain thinks in concrete ways, such as the literal meaning of words and mathematical calculations, while the right side thinks in more abstract ways, such as symbolism and gestures [source: Gutman].
Because the two sides of your brain process information differently, they work together to keep your emotions in check. Here's an easy way to explain it: The right hemisphere identifies, and the left hemisphere interprets. The right brain identifies negative emotions, like fear, anger or danger. It then alerts the left brain, which decides what to do by interpreting the situation and making a logical decision about how to act in response.
It's a great system, unless something happens and one side of the brain can't do its job. Without the left brain, the right brain would be overcome with negative emotions and not know how to respond to them. And without the right brain, the left brain would not be as good at identifying negative emotions [source: National Institute of Neurological Disorders and Stroke].
It may seem like common sense: Recalling a negative memory can put you in a bad mood, and thinking about a happy memory can put you in a good mood. But there's actually scientific evidence to back that up. Studies even show that this effect is taking place whether or not we're aware of it.
So what's the big deal? It turns out that memory recall can be used to regulate mood in people who are experiencing depression, because thinking about positive memories causes the brain to release dopamine. So when someone tells you to cheer up, it may be a simple matter of thinking happy thoughts [source: Gillihan].
Not surprisingly, memories of previous experiences influence how you respond emotionally to situations. If you once nearly drowned, you might experience fear around water. If a previous love had a wandering eye, you might feel jealousy when a current flame looks at another person. What's more, the intensity of the previous experience affects the intensity of the current emotion. For example, a soldier who has had extensive combat experience or traumatic combat experience will likely have more intense anxiety later on.
Preconceived ideas also affect your emotions. Anticipation and your expectations, which are driven by memories of previous events, affect the intensity of an emotional reaction [source: Frijda].
Want to know more about the brain and your emotions? The links on the next page will give your brain some new information to process.
HowStuffWorks finds out why people often ignore their instincts and whether they should listen.
More Great Links
- Banich, Marie T., and Rebecca J. Compton. "Cognitive Neuroscience, Third Edition." Cengage Learning, 2011.
- BBC. "A Job for the Hippocampus." (July 24, 2011). http://www.bbc.co.uk/radio4/memory/understand/hippocampus.shtml
- Brodal, Per. "The Central Nervous System: Structure and Function, Second Edition." Oxford University Press, 2010.
- Dozier, Rush W., Jr. "Why We Hate: Understanding, Curbing, and Eliminating Hate in Ourselves and Our World." Mcgraw-Hill Professional, 2003.
- Fiori, Nicole. "Cognitive Neuroscience." Armand Colin Publisher, 2006.
- Frijda, Nico H. "The Emotions." Press Syndicate of the University of Cambridge, 1986.
- Gillihan, Seth J. at al. "Memories affect mood: Evidence from covert experimental assignment to positive, neutral, and negative memory recall." Center for Cognitive Neuroscience, Department of Psychology, University of Pennsylvania, July 20, 2006. (July 13, 2011). http://www.psych.upenn.edu/~mfarah/Emotion-Memoriesaffectmood.pdf
- Gorman, Phil. "Motivation and Emotion." Psychology Press, 2004.
- Gutman, Sharon A. "Quick Reference Neuroscience for Rehabilitation Professionals." SLACK Incorporated, 2008.
- Kalat, James W. "Biological Psychology, Tenth Edition." Cengage Learning, 2009.
- Lewis, Michael at al. "Handbook of Emotions, Third Edition." The Guilford Press, 2008.
- Licinio, Julio, and Ma-Li Wong. "Biology of Depression: From Novel Insights to Theraputic Strategies, Volume I." Wiley-VCH, 2005.
- Michael-Titus et al. "The Nervous System." Elsevier Health Sciences, 2007.
- National Institute of Neurological Disorders and Stroke. "Brain Damage Disrupts Emotions and Mood." National Institutes of Health, May 5, 1992. (July 13, 2011). http://www.ninds.nih.gov/news_and_events/news_articles/pressrelease_braindamage_050592.htm
- National Institutes of Mental Health. "Imaging Identifies Brain Regions and Chemicals Underlying Mood Disorders; May Lead to Better Treatments." National Institutes of Health, May 6, 2008. (July 20, 2011). http://www.nimh.nih.gov/science-news/2008/imaging-identifies-brain-regions-and-chemicals-underlying-mood-disorders-may-lead-to-better-treatments.shtml
- Nazario, Brunilda, MD. "Serotonin: 9 Questions and Answers." WebMD. (July 21, 2011). http://www.webmd.com/depression/recognizing-depression-symptoms/serotonin
- Nicholas, Lionel. "Introduction to Psychology, Second Edition." UCT Press, 2008.
- Thompson, Jason. "Emotionally Dumb: An Overview of Alexithymia." Soul Books, 2009.
- Zillmer, Eric et al. "Principles of Neuropsychology." Cengage Learning, 2008.