pheromones

what is a pheromone?

a chemical produced and released into the enviornment by an animal affecting the behavior or physiology of others in its own species

what is some suggestion of pheromones in humans?

• menstrual cycles in groups of women

• olfactatoy recognition of a newborn by its mom

• exude different odors based on mood

primer pheromones

cause slow, long term physiological changes like hormone effects (maybe in humans)

signaling pheromones

produce rapid behavioral effects like mating

what are two potential human phereomones?

1. androstadienone (AND) in male excretion and sweat

2. estratetraneon (EST) in female urine

explain Zhou et al (2014)

• aim: see if AND or EST influences human mating behavior

• process: used four groups of straight men and women and gay men and women. they watched stick figures walk and determine the gender. in the first condition, they smelled cloves with AND then with EST then in control, nothing

• results: AND showed effects in straight women and gay males only showing they percieved walkers are masculine. EST biased straight men and some lesiban to femminine walks; pheromones influence the communication of gender info in a sex-specific manner

limits of Zhou et al

• exposed to high atrifical levels of pheromones

• not a clear study of sexual attraction but of percieving if a person’s walk was feminine or masculine; not reliable measure of sexual behavior

• small sample

explain Douce et al (2009)

• aim: role of secretion of areolar glands in suckling behavior in 3-day old infants

• procedure: compared infants breathing rate and behavior to different stimuli and types of milk and secretions from aerola

• result: showed infants sucked once exposed to secretions of areolar glands; increase in breathing rate; shows aerolar odor may initiate a chain of behavior/physiological events that lead to attatchment to mom

problems with pheromone arguments

1. human sense of smell is too complex with too many odor receptos and genetic variations

2. many body odors are caused by bacteria not sectretions; not everyone has these odors; less universal

3. culture tells us what smells good and bad

pheromones and aggression in animals

they will attack those of their own species if they feel threatened to protect themselves. male lions attack males but not females

how do prove a pheromone exists?

1. design a repeatable experiment, bioassy

2. show smell molecule (ordorant) causes a particular effect

3. isolate variables until you find protein, etc.

how do animals detect it?

through a structure called vomeronasal organ, a tube at the base of the nasal cavity directly behind the nostrils that is filled with sensory neurons. absent in birds and non primate mamals. removal eliminates territorial aggression and marking in males. humans lack this

explain Mishor et al (2021)

• aim:

• procedure:

• results:

what do evolutionary psychologists argue where our behavior come from?

our behaviors are result of natrual selection

explaim Wedekind (1995)

• aim: study the Major Histocompability Complex (a group of genes that influence immune system. MHC genes recognize pathogens. the more diverse genes, the stronger the immune system. they are expressed co-dominantly — equal expressed from both parents. we want partners of different MHC genes for strongest immune systems). evolutionary scientists argue that smell is a sign of MHC. Wedekind wanted to see if women are attracted to a man using MHC and smelly t-shirts

• procedure: with a wide variance of MHC, an equal number of men and women were chosen. men wore a tshirt for two nights. everyone’s sense of smell was wiped clean and women were trained on how to smell better. after a few days, the women smelled each of the 7 t-shirts during menstration. three of the seven boxes had shirts from men with different MHC, three with similar, one unworn as control. they scored the odors from 0-10 for intensity and pleasantness

• result: women score male body odors are better when they were different from their own. opposite though when the women were taking birth control

evaluate Wedekind (1995)

Benefits

• successfully replicated by Jacob et Al and supported by Yamazaki et al’s 1976 study with mice

• couples who suffer from multiple miscarriages share a higher proportion of their MHC than control couples. newborn babies of such couples usually have a reduced birth mass too

• demand characteristics were minimized by using a double-blind experiment

• met ethical standards as consent was given and debriefed

Limits

• reductionist approach; oversimplifies mating to MHC and ignores cognitive and sociocultural factors

• not very generalizable

demand characteristics

cues in a research setting that hint at the study's true purpose, causing participants to change their behavior to match what they think the researcher expects, rather than acting naturally

key ideas about epigenetics

• identical twins are born with the same genetic code but may change over time due to diet and stress (DNA same, expression not)

• changes passed down to next generation

• epigenetic info determines which genes are expressed

• shows genes are not deterministic

why is epigenetics important?

• who you are is a combo of genome and enviornment. nature vs nurture model outdated

• diathesis stress model is resulted from enviornmental factors

• stress, diet, and life habits affect gene expression. epigenome is inheritable

explain Hamer et al (1993)

• aim: examined the possibility of homosexuality being a sex-linked trait, linked to the x chromosomes. meaning the trait would be passed down to the offspring by the mom

• procedure: examined the family trees of openly gay men and dna samples from them.

• result: found a remarkable concordance for 5 genetic markers on a section of the x-chromosome Xq28 via linkage analysis. statistical probability of match being random was 1 in 100,000