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CHAPTER 12 – PSYC 355
CHAPTER 12
Sex: Evolutionary, Hormonal, and Neural Bases
There are 4 stages of reproductive behavior:
1. Sexual attraction
2. Appetitive behavior
3. Copulation
4. Post-copulatory behavior
- Reproductive behavior is different from sexual
behavior
Stage 1: sexual attraction
- is 1st step in mating behavior for many animals
- Animals emit many stimuli such as visual cues
pheromones These attract members of the
opposite sex
- Pair bonds: this is a durable and exclusive
relationship between a male and female there are
2 types of pair bonds: social monogamy and sexual
monogamy, and they are different from each other
- An animal can have social monogamy with
another individual of the opposite sex but engages
in sexual relationships with other animals
- Social monogamy is important for the survival of
the offspring has evolutionary advantage.
- Oxytocin and vasopressin are implicated in
monogamy and in human pair bonding.
- Females are attracted to particular traits in males
such as feather types in peacock this is sexual
selection has evolutionary purposes.
- Sexual selection is the process by which members
of one biological sex chose one from the opposite
sex
& also refers to competition between individuals of
the same sex in order to access other mates from the
opposite sex
- Superior level of genetic fitness looks more
sexually desirable, looks more attractive.
- Females egg release is synchronised with her
fertility peak and readiness to copulate
Stage 2: appetitive behavior
- Establishes, maintains and promotes sexual
interaction.
- Appetitive behavior is species-specific.
- Proceptive behavior is when the females show
appetitive behavior.
examples in females: ear wiggling, darting and
hopping in female rats.
examples in males: sniffing, singing, nest
building.
Stage 3: copulation:
1. Coitus is the sexual act
- Involves intromissions (penis in & out of
vagina)
- Male ejaculates semen into female
2. Refractory phase: period during which the
individual cannot do copulation
Here there is a temporary decrease in the sexual
attractiveness of the partner
- Following ejaculation, there is a refractory phase
during which it’s impossible for the male to
ejaculate again
3. Coolidge effect: faster resumption of mating
behavior with a novel partner
- By the Coolidge effect, you can decrease the
refractory phase by introducing a new female to a
male.
- Female that is willing to copulate is called in heat,
or in estrus or sexually receptive
Stage 4: Post-copulatory behavior
- includes parental behavior to nurture offspring
- Copulatory lock is when the penis swells
temporarily and cannot be withdrawn from the
female. Occurs in dogs and some mice.
- There is temporary inhibition of sexual attraction.
- Copulation brings gametes together
- Internal fertilization tales place inside the female
body here the fusion of sperm and ovum
produces a zygote (fertilized ovum)
- External fertilization tales place outside the
female’s body example: some fish and
amphibians that release eggs in water.
- The hormonal cycle of female rats is 4-5 days it
releases an egg every 4-5 days and she display
proceptive behavior synchronized with egg release.
- The proceptive behavior includes ultrasonic
vocalizations to attract male rats these sounds are
very high pitched and cannot be detected by humans
- after the female emit these ultrasonic
vocalizations, the male is attracted to the female and
starts to mount her and grab her flanks.