Motivation and emotion/Book/2017/Serotonin and motivation
How does serotonin affect motivation?
Overview[edit | edit source]
Motivation occurs in your everyday life. Did you feel like getting out of bed this morning? Having a glass of water? Did you go to the gym today? If you answered yes to these questions then your motivation to complete everyday tasks is high. However not everyones motivation is. Sometimes you can't get out of bed, don't want that glass of water, or to go to the gym. The question asked by psychologists is why though? What makes an individual do these things? Or better yet, not do these things. Many scientific studies have investigated this question from Drive Reduction theory to Instinct Theory. Recently scientists have been looking at the effect of serotonin on motivation. That being, how does this neurotransmitter affect a concept as broad as motivation? Throughout this chapter the individual roles of serotonin and motivation are discussed, along with an in-depth view of the research discussing the current question "How does serotonin affect motivation?".
Serotonin[edit | edit source]
Serotonin (5-HT) plays a key part in the reactions of the brain and other tissues. Serotonin-producing neurons are located in an area of the brainstem called the raphe nuclei. Because these neurons project their axons to multiple brain regions, serotonin acts widely across the brain (Champalimaud Center, 2017) affecting the activity of nerve cells leading to a key role in arousal, mood, aggression, and the sleep-wake cycle (Oxford University Press, 2016).
Serotonin has commonly been associated with the modulation of emotional states, circadian rhythm, food intake, reproduction and cognition. Recent studies have found that emotional dysregulation and cognitive control failures may by modulated by 5-HT and because of this historically focused role of serotonin on emotional regulation, there have been fewer studies investigating the effects of 5-HT on motivation (Izquierdo, Carlos, Ostrander, Rodriguez, McCall-Craddolph, Yagnik, and Zhou, 2012).
How might this neurotransmitter physiologically affect motivation?
Research in this area is new and therefore it remains unclear what the effect might be. For example scientists found that stimulation to the raphe nuclei reduced mice locomotive speed by up 50% (Champalimaud Center, 2017). This means that the stimulation caused an increase of motivation in mice, however locomotive speed was affected only when the animals were not immersed in a particularly engaging task at the time of stimulation. The same stimulation did not have any effect if the animal is already engaged in a specific task, such as running to get a reward (Champalimaud Center, 2017). This shows that the motivation within this study was subjective and may not always occur. However, the remaining question is how else might serotonin affect motivation. Is it always an increase motivation or can it also decrease motivation?
Motivation[edit | edit source]
The study of motivation has been a prominent part of research in psychology. Early on many studies were done to investigate drive-based learning theories as a function of arousal, incentive, and habit. From this branched motivation studies in personality, social, clinical, industrial and organisational psychology (Kanfer, 1990). Motivation comes from the latin term 'Movere' , which means "to move". Where a students' motivation is referred to as what "moves" them to pick up their textbook and what "moves" them to continue reading that textbook (Jang, Conradi, McKenna and Jones, 2015) .
Motivation can also be defined through six factors; described through reading (Jang et al., 2015):
- Attitude: a set of acquired feelings about reading that consistently predispose an individual to engage in or avoid reading
- Interest: A positive orientation toward reading about a particular topic
- Value: An individual's beliefs about the extent to which reading is generally useful, enjoyable, or otherwise important
- Self-efficacy: An individual's judgment of ability to accomplish a specific reading task
- Self-concept: An individual's overall self-perception as a reader, including a sense of competence and the role ascribed to reading as a part of personal identity
- Goal: An individual's orientation and intentions toward reading
It is said that there are three main approaches surrounding motivation, these are:
- Humanistic Approaches: Maslow's Hierarchy of Needs, Alderfer’s ERG Theory, Herzberg’s Two Factor Theory, McClelland's Learned Needs Theory
- Cognitive Approaches: Expectancy Theory, Equity Theory/ Social Comparison, Goal Setting Theory
- Biological Approaches: Instinct Theory, Drive Reduction Theory, Arousal Theory
Serotonin's possible affect on motivation theory
Serotonin is said to affect emotional states, circadian rhythm, food intake, reproduction and cognition. This means that serotonin's affect on thoughts, feelings and mood might lead to an effect on an individuals motivation. For example if there is a lack of serotonin an individual might become depressed, this depressed state might lead this person to feel a lack of motivation in day to day life. Additionally an individual might feel more or less motivation to eat depending on their serotonin levels.
Psychological Theory and Research[edit | edit source]
How does serotonin affect motivation?
The first way to consider this question is to look back at the six motivational factors: attitude, interest, value, self-efficacy, self-concept and goals. A depletion or negative intention towards these factors can lead to a reduction in motivation. Serotonin can be a cause of this depletion (Oxford University Press, 2016) due to its role in regulating eating, sleeping and moods. More specifically, an individualsinterest, value and goals could be a victim to the depletion of serotonin in the system, as one may feel more depressed, fatigued and uninterested. However while this is important to consider, there is limited to no research to directly support such claims and therefore is it required to discuss in further detail the theories and studies behind the relationship between motivation and serotonin.
Maslow Hierarchy of Needs[edit | edit source]
[[wikipedia:Maslow's_hierarchy_of_needs|Maslow Hierarchy of Needs]] states that people are motivated to achieve certain needs. When one need is fulfilled a person seeks to fulfil the next one, and so on. This lead Maslow (1943) to create the hierarchy pyramid with five levels stated below (Poston, 2007):
- Biological and Physiological needs - air, food, drink, shelter, warmth, sex, sleep.
- Safety needs - protection from elements, security, order, law, stability, freedom from fear.
- Love and belongingness needs - friendship, intimacy, affection and love, - from work group, family, friends, romantic relationships.
- Esteem needs - achievement, mastery, independence, status, dominance, prestige, self-respect, respect from others.
- Actualisation needs - realising personal potential, fulfilment, seeking personal growth and peak experiences.
One must satisfy lower level basic needs before progressing on to meet higher level needs. Once these needs have been satisfied, one may be able to reach the highest level called actualisation (Poston 2009).
This leaves the question of how does serotonin affect the hierarchy and therefore motivation. Simply put a person must start at the bottom of the pyramid with biological needs, and serotonin has the potential effect on food and water intake, sex and sleep. Therefore if there is a lack of serotonin than an individual will not be able to move to safety needs and so on. However if there is an excess amount of serotonin it may be possible that an individual become extremely motivated, therefore meeting biological needs and so on, unless there are other influences on this happening. As shown above in the serotonin section, this increase in motivation is possible as the mice were found to have a 50% increase in locomotive speed (Champalimaud Center, 2017).
Drive Reduction Theory:[edit | edit source]
Drive Reduction Theory of motivation became popular during the 1940s and 1950s as a way to explain behaviour, learning, and motivation and was created by behaviourist Clark Hull. According to the theory, the reduction of drives is the primary force behind motivation (Cherry, 2017). Hull (1943) built the theory around the concept of homeostasis and suggested that all motivation arises as a result of these biological needs.
Hull (1943) used the term "drive" to refer to the state of tension or arousal caused by biological or physiological needs. Thirst, hunger and the need for warmth are all examples of drives. A drive creates an unpleasant state; a tension that needs to be reduced (Cherry, 2017). To reduce this state of tension humans seek ways to reduce this tension, for example when you're thirsty you get a drink, when you're hungry you eat.There a two categories of 'drives'. Primary drives, which are innate drives (hunger, thirst ect.) and secondary drives, which are learnt through conditioning (e.g. Money).
The drive reduction theory is similar to the biological needs in Maslow's hierarchy of needs. How drive reduction states, that it is the reduction of the drives that motivates an individual. Therefore an individual will want to eat, as it reduces the uncomfortable feeling of the drive to eat. What this means for serotonin's affect is that there could be lack of drive created there for a lack of reduction. If serotonin is affecting an individual's drive to eat, drink or have sex in a depleting way, then the individual may not perform these acts. This is showing a direct lack of motivation due to the lack serotonin. However similarly to the hierarchy, an increase of serotonin could create a motivation to reduce the drives to an extreme level . Meaning an individual may feel the motivation to eat or drink more than normal. This could have extreme negative outcomes as over eating and drinking can become dangerous. However it is important to remember that if serotonin levels are at normal, they might be contributing a great deal to these motivations in a safe way.
Limitations[edit | edit source]
Maslow's Hierarchy of Needs
A major question asked of the Hierarchy is how well does it relate directly to humanistic psychology. The primary limitation is that anyone in society can regress back to, or value an alternative aspect of the hierarchy pyramid in a way that is not parallel with Maslow's model (Poston, 2009), that being there is no ecological validity. Another major limitation of this theory is the concept of self-actualisation (Poston, 2009), that being how does one actually reach this point and is it fair to say one person is not actualised, even if they themselves feel satisfied.
Drive Reduction Theory
A major limitation of drive reduction theory is that it fails to explain human actions that produced, rather than reduced, tension (Strickland, 2001). Many people enjoy riding roller coasters or watching scary movies (pleasure-seeking activities), despite the fact that these activities may cause fear and anxiety. There are also limitations in the theory having trouble explaining why humans and other animals voluntarily increase tension by exploring their environments, even when they are not hungry or thirsty (Stricklans, 2001) along with proponents of drive-reduction arguing that one is never in a state of complete fulfilment, as there are always drives that need to be satisfied.
Research[edit | edit source]
After looking at the theories of Drive Reduction and Hierarchy of Needs, it is important to also consider the empirical research done on serotonin's affect on motivation.
Motivational influence of aversive stimuli[edit | edit source]
An aversive stimulus is an unpleasant event that is intended to decrease the probability of a behaviour when it is presented as a consequence (i.e., punishment). However, an aversive stimulus may also increase the probability of a behaviour when it is removed as a consequence, and in this way it will function as negative reinforcement (Pritchard and Chong 2011). Hebart and Gläscher (2014) examined this further in reference to serotonin through their study titled: Serotonin and dopamine differentially affect appetitive and aversive general Pavlovian-to-instrumental transfer. Their aim was to investigate the effect of dopamine and serotonin in a general Pavlovian-to-instrumental transfer (PIT) task. This was then used to measure the effect of appetitive and aversive Pavlovian cues on instrumental responses (Hebart and Gläscher 2014). Results demonstrated a differential involvement of serotonin and dopamine in motivated behaviour. Researchers suggested that reductions in serotonin enhance the motivational influence of aversive stimuli on instrumental behaviour (Hebart and Gläscher 2014).
Overall, Hebart and Gläscher (2014) were able to demonstrate a casual relationship between serotonin and motivation. The results showed that a reduction in serotonin enhanced an individuals negative behaviour towards goal directed behaviour. This also fits in with an individuals orientation or intention towards the goal (Jang et al., 2015).
Sexual Motivation[edit | edit source]
The Selective Serotonin Reuptake Inhibitor (SSRI), fluoxetine reduces sexual motivation in male rats (Matuszcyk, 1998). This study aimed to enable further characterisation of the mechanisms underlying SSRI-induced sexual side effects. Matuszcyk (1998) found support for the assumption that SSRIs reduce sexual drive in male rats. SSRIs are typically used as antidepressants in the treatment of major depressive disorder and anxiety disorders. They are believed to increase serotonin (Sangkuhl, Klein & Altman, 2009). This means that the increase of serotonin used through an SSRI leads to a lack of sexual motivation, at least in male rats and possibly human males as well. Providing evidence for the hierarchy of needs and drive reduction theory, as sexual motivation is a biological need/drive in both theories.
Serotonin uptake inhibitors[edit | edit source]
Focusing on the area of SSRIs again Amit, Smith, and Gill (1991) focused on its effect on motivated consummatory behaviours such as food, alcohol and drugs. There is increasing evidence indicating that food consumption and fluid intake are attenuated by 5-HT uptake inhibition. Findings from the study suggested that 5-HT uptake inhibition may result in nonspecific modification of motivated behaviour in general. So while this did not answer the specific question presented, the study did show the serotonin may affect motivated behaviour in general .
While these findings are not easily applicable, they are indicative of serotonin affecting food, alcohol and drug intake. Meaning, that with further research in this area, it could be possible to conclude that these consummatory behaviours that underly motivational theory, could be affected by serotonin.
Incentive Motivation[edit | edit source]
Browne and Fletcher (2016) conducted a study that aimed to find if acute pharmacological elevation of serotonin activity decreases operant responding for primary reinforcers. This suggesting that serotonin reduces incentive motivation. Experiments examined whether chronic and acute disruptions of serotonin transporter actively altered incentive motivation through the measurement of responding to three different reinforcers: a primary reinforcer a conditioned reinforcer, and an unconditioned sensory reinforcer (Browne and Fletcher, 2016). Results showed a powerful inhibitory function for serotonin in the control of incentive motivation.
Within this study incentive motivation is said to be an individual's motivation to do things because of external rewards (Arana, Parkinson, Hinton, Holland, Owen and Roberts, 2003). Therefore results showed that serotonin causes an inhibitory function in the motivation to do things because of external rewards. While it is believed that individuals should not do things only for an external reward, it is a big motivator within society. People will be more motivated if they are going to receive money (the external reward) for doing a chore, than if they were to receive no money.
Jennifer is 28 year old woman who normally leads a busy, happy life of work and family. However recently Jennifer has come to you stating that lately she feels less happy and it's as though she has no motivation to get out of bed, or go to work. However she is happy to stay at home and be with her family. Jennifer has no prior medical and psychological issues, but has stated that she has felt like this before.
From what you've read why might Jennifer be feeling this lack of motivation in her work life?
Hint: Consider both theory and biological aspects
Implications[edit | edit source]
Many implications can come out of identifying a casual relationship between serotonin and motivation. One of these implications is being able to gain a better overall understanding of the psychological aspects of motivation. Current and past studies on motivation have been majorly theoretically based; therefore attributing serotonin to the activation or depletion of motivation can help the area to expand. Leading to a more reliable understanding of motivation. However there is still a long way to go in the research and serotonin is not the only neurotransmitter that could affect motivation, e.g Dopamine.
Another implication is that serotonin can possibly affect goal directed behaviour. Goals are used in everyday life, people set individual goals, daily goals, yearly goals and so on. However one thing people struggle with is the motivation to complete these goals, especially long term ones. Therefore learning that a lack of serotonin can lead to negative attitudes towards goal orientated behaviour (Hebart and Gläscher 2014), means that with further research scientists may be able to identify how much serotonin is needed to for a positive attitude towards goal orientated behaviour. This could be particularly helpful in situations such as university, weight loss, ect. (if proven ethical).
Most importantly from the research and theories above there is a clear indication that serotonin affects an individual's motivation to eat, drink, sleep ect. For eating and drinking behaviours it could prove to be effective in many ways. For example eating, a person that is struggling to lose weight because they are motivated to eat more than usual or on the other end of the scale and is anorexic, they might be able to change their serotonin levels to increase or decrease their motivation to eat. Similar goes for alcoholics, in that they might be able to decrease their serotonin levels in order to reduce their motivation to drink.
Test Your Knowledge[edit | edit source]
Conclusion[edit | edit source]
Serotonin (5-HT) acts widely across the brain affecting the activity of nerve cells leading to a key role in arousal, mood and aggression. These factors and many more can lead to serotonin affecting an individual's motivations. Motivations can be described through one's attitude, interest, value, self-efficacy, self-concept and goal. All these factors along with motivational theory could be affected by serotonin. Maslow's Hierarchy of Needs and Drive Reduction Theory were highlighted as important key theories due to their biological components. Investigating these theories constructs and more was done through research on sexual motivation, serotonin re-uptake inhibitors and more. All together these points provide important implications for the future including help with goal oriented behaviour and eating behaviours.
Currently the studies contributing to the understanding of "how does serotonin affect motivation" are broad and unclearly defined, particularly in how it does it. However from the above research it is evident that serotonin plays a role in affecting motivation. Research is suggestive of serotonin affect food and water intake, goal behaviours ect. Therefore future directions for this research should continue to investigate the overall role of how serotonin affects motivation. However more specifically, future studies should clearly define the current findings, that being to what extent does serotonin affect an individual's motivation to drink, eat, goal attitudes/behaviours and so on.
Jennifer Case Study:
Jennifer has had a depletion in serotonin levels, leading to those feelings of depression and lack of motivation. Her family gives a natural rise in her serotonin levels, hence her feeling motivated to be with them. SSRIs may be helpful in returning her to a normal life.
See also[edit | edit source]
- Serotonin and emotion (Book chapter, 2014)
References[edit | edit source]
Arana, F. S., Parkinson, J. A., Hinton, E., Holland, A. J., Owen, A. M., & Roberts, A. C. (2003). Dissociable contributions of the human amygdala and orbitofrontal cortex to incentive motivation and goal selection. Journal of Neuroscience, 23(29), 9632.
Browne, C., & Fletcher, P. (2016). Decreased Incentive Motivation Following Knockout or Acute Blockade of the Serotonin Transporter: Role of the 5-HT2C Receptor. Neuropsychopharmacology, 41(10), 2566-2576. http://dx.doi.org/10.1038/npp.2016.63
Champalimaud Center for the Unknown (2017). More Serotonin, Less Motivation? It Depends on the Circumstances. NeuroscienceNew. Retrieved February 14, 2017 from http://neurosciencenews.com/serotonin-motivation-6112/
Cherry, K. (2017). How Does Drive Reduction Theory Explain Human Motivation?. Verywell. Retrieved 31 October 2017, from https://www.verywell.com/drive-reduction-theory-2795381
Hebart, M., & Gläscher, J. (2014). Serotonin and dopamine differentially affect appetitive and aversive general Pavlovian-to-instrumental transfer. Psychopharmacology, 232(2), 437-451. http://dx.doi.org/10.1007/s00213-014-3682-3 Heffner, D. (2017). Chapter 7: Section 2: Motivation | AllPsych. Allpsych.com. Retrieved 5 November 2017, from https://allpsych.com/psychology101/motivation/
Izquierdo, A., Carlos, K., Ostrander, S., Rodriguez, D., McCall-Craddolph, A., Yagnik, G., & Zhou, F. (2012). Impaired reward learning and intact motivation after serotonin depletion in rats. Behavioural Brain Research, 233(2), 494-499. http://dx.doi.org/10.1016/j.bbr.2012.05.032
Jang, B., Conradi, K., McKenna, M., & Jones, J. (2015). Motivation. The Reading Teacher, 69(2), 239-247. http://dx.doi.org/10.1002/trtr.1365
Kanfer, R. (1990). Motivation theory and Industrial/Organizational psychology. In M. D. Dunnette and L. Hough (Eds.), Handbook of industrial and organizational psychology. Volume 1. Theory in industrial and organization psychology (pp. 75-170). Palo Alto, CA: Consulting Psychologists Press.
Matuszcyk, J. (1998). The Selective Serotonin Reuptake Inhibitor Fluoxetine Reduces Sexual Motivation in Male Rats. Pharmacology Biochemistry And Behavior, 60(2), 527-532. http://dx.doi.org/10.1016/s0091-3057(98)00010-0 Poston. (2009). the surgical technologist (pp. 347-353). Retrieved from http://www.ast.org/pdf/308.pdf
Pritchard, & Chong. (2011). Aversive Stimulus. Encyclopedia Of Child Behavior And Development, 190-190. http://dx.doi.org/10.1007/978-0-387-79061-9_265
Sangkuhl, K., Klein, T., & Altman, R. (2009). Selective serotonin reuptake inhibitors pathway. Pharmacogenetics And Genomics, 19(11), 907-909. http://dx.doi.org/10.1097/fpc.0b013e32833132cb
Serotonin (2016). (2nd ed.) Oxford University Press.
Strickland, B. B. (2001). The gale encyclopedia of psychology (2nd ed.). Detroit, MI: Gale Group.