Oxytocin is a hormone produced in the hypothalamus (a region of the brain that links the nervous system to the endocrine system via the pituitary gland). It is released either directly into the blood via the pituitary gland, or to other parts of the brain and spinal cord. Oxytocin is often called the ‘love hormone’. It is known to increase feelings of generosity, relaxation, and facilitates relationship formation and positive communication. It was first acknowledged in 1900s, researchers recognized that it is released during breastfeeding which triggered certain emotional feelings in women. It was concluded that Oxytocin was related to social attachment or love.
At first, Oxytocin was also supposed responsible for stress reduction because the level of Oxytocin was seen to go higher when a ‘man would hug his wife’ - whilst feeling more calm. To see this if this theory was true, a recent study done by Morhenn et al. (2008) carried out a “massage experiment”. They randomly assigned 96 students to 3 different groups: massage and trust, rest and trust, and massage only group. The massage was 15 minutes long and the ‘rest’ part involved the participant to rest in the room for the same amount of time. The ‘trust’ part was measured the tip given by the participants. The first group that was given massage was tested immediately for oxytocin levels. The researchers concluded that the massaging itself did not make a significant rise in the oxytocin levels, however it seemed to prime participants to sacrifice money- an act that occurred as Oxytocin level raised. So, it was concluded that Oxytocin effect on behavior is to increase ‘generosity’ with others.
Another hormone that may affect behavior is Adrenaline. It is produced by the adrenal gland located in the kidney. When produced, the body stimulates the heart-rate, contracts blood vessels, dilates air passages, and has a number of other minor effects. Like Oxytocin, Adrenaline is naturally produced in high-stress or physically exhilarating situations. The term "fight or flight" is often used to characterize the circumstances under which adrenaline is released into the body. It is an early evolutionary adaptation to allow better coping with dangerous and unexpected situations. With dilated air passages, for example, the body is able to get more oxygen into the lungs in a timely manner, increasing physical performance for short bursts of time. In general, it makes the body either fight with the situation encountered or run away from it. A study done by Schechter, S. & Singer, J.E. (1962) showed that Adrenaline does not affect everyone. However, since a very few amount of people were not affected by the adrenaline they had injected, the proof may be unreliable. The experiment also lacked ecological validity and the participants were males.
Hence, these are the two hormones that affect the human behavior.
Refrences :
Peterson Book Psychology IB