Hormones & Pheromones (and their effect on human behavior)

Hormones

any chemical substance that is secreted naturally into the blood and can influence physiological processes & thereby influence behavior

Oxytocin: affects social bonding, affiliation & trust (mother-child attachment)

Cortisol: at moderate levels increases sugar levels and boosts energy; at high levels causes stress and affects memory

Adrenaline: responsible for arousal and fight or flight response

Cahill & McGaugh (1995): Hormones Study

Adrenaline & Emotional Memories Study

Aim: to investigate the role of adrenaline and the amygdala in the creation of emotional memories

Procedure: participants were split up into two conditions, with two types of stories

• neutral story: heard a boring story about a hospital visit

• emotional story: heard a dramatic story involving a traumatic accident

• Two weeks later, participants were tested on their memory of the story's details

  • in a follow-up experiment, participants in the emotional story condition were given a beta-blocker to prevent adrenaline from accessing the amygdala

Findings: those in the emotional story condition recalled significantly more details about the story than those in the neutral story condition did

• when adrenaline was blocked, details recalled by the emotional story group were similar to that of the neutral story condition

Adrenaline plays a key role in memory consolidation for emotionally arousing events

Baumgartner et al.: Hormones Study

Aim: investigating whether increased levels of oxytocin would affect levels of trust

Procedure: one player (the investor) is given a sum of money and decides whether to keep it all or share it with the other player (the trustee)

• if the sum is shared, it is tripled

• the trustee then decides if they will keep the tripled money or share it back with the investor

• some participants were given oxytocin, while others were given a placebo drug (control)

• participants were repeatedly told that their trust had been betrayed

• Participants placed in an fMRI scanner

Findings: The placebo group's trust was reduced after betrayals, causing them to invest less money

• the oxytocin group continued to trust at the same level despite the betrayals (invested the same amount of money)

• fMRI showed that oxytocin group had reduced activity in the amygdala (area of the brain associated with fear) than that of the control group

Oxytocin plays a role in maintaining trust even after a betrayal

Pheromones

chemical substance produced and released into the environment by an animal affecting the behavior or physiology of others or its own species

ANIMALS release pheromones

Signalling Pheromones: type of pheromone that produces rapid behavioural effects in animals

Wedekind (1995): Pheromones Study

Major Histocompatibility Complex (MHC): molecules that help the immune system to identify pathogens and activate immune responses

• each person has a unique MCH footprint; has an effect on our body odor

Aim: to determine whether one's MHC would affect mate choice

Procedure: sample of female and male students whose MHC genes were tested; a wide range of MHC genes represented

• men were asked to wear a t-shirt for two nights, wash with non-perfume detergent, and not use perfume or cologne or engage in acts that would affect their smell (eating spicy food, having sex, smoking, drinking)

• 3 of the t-shirts were worn by men with a similar MHC gene to the woman, 3 worn by men with a dissimilar MHC gene, and an unworn T-shirt as a control

• women were asked to rank the smell of the 7 shirts in terms od intensity, pleasantness and sexiness

Findings:

• women scored the body odors of men with different MHC genes higher than those of men with similar MHC genes to them

• this pattern wad reversed when the women were taking oral contraceptives

People are attracted to people with different MHC genes as a greater diversity/varying of MHC genes results in offspring with a stronger immune system

Limitations:

• Strengths

  • highly standardized and easy to replicate

  • used double-blind control to eliminate both researcher bias and demand characteristics

  • controls set for diet, sex, and an individual's sce

• Limitations:

  • has been mixed results of the replications of this study

  • original premise that rat's selection of mates is based on MHC has been disproven

  • is not about a pheromone but rather a human scent that is created as a result of genetic coding for the immune system

  • human smell is not only influenced by MHC but also by bacteria and diet

  • difficult to argue that it signaled "mating behavior"

  • "pleasantness”that was measured is not the first step of pheromonal mating that takes place in animals

Zhou et al. (2014): Pheromones Study