Chapter 8: Social behavior Flashcards
What is social behavior?
Encompasses interactions between individuals from which one or more of the individuals benefit
Aggressive behavior
Affiliation
Courtship
Parental behaviors
Affiliation: social behaviors that bring animals together
Territorial/Aggression: social behaviors that keep animals apart
Affiliation
social behaviors that bring animals together
Territorial/Aggression
social behaviors that keep animals apart
Origins of Prosocial Behaviors
Mcdougall hypothesized that prosociality was a natural consequence of parental instincts, the result of “tender emotions” originally directed towards offspring that were later co-opted to promote the helping of others.
Oxytocin would seem a likely substrate for these tender emotions.
Oxytocin increases activation in reward system and empathy system.
Hormones (like Oxytocin) associated with regulation of parental behavior may have co-opted over evolutionary time to serve as modulators of prosocial behaviors.
Vampire bat
shares meal with offspring and may also share with unrelated animals
Relies on social recognition, social memory, strong social bonds, and reciprocity
Social behavior as an ‘offshoot’ of parental behavior
Social vs. solitary behaviors:
species and seasonal differences
Breeding season predicts social behavior in female meadow voles
Territorial aggression vs. affiliation
During winter months, females prefer contact with other females to males; do not have to compete for males
Costs of group living
Increased ease of disease transmission
Increased competition for food, mates, and nesting sites
Increased susceptibility to predators
Benefits of group living
Group defense of resources
Elevated foraging efficiency
Anti-predator detection and defense
Increased mating opportunities
Social Affiliation Behavior
Thought to have evolved from parental and reproductive behaviors
In many instances, hormones that mediate reproductive and parental behaviors, mediate affiliation as well.
Hormonal systems for social behavior highly conserved.
Nonapeptides
An oligopeptide containing 9 amino acyl residues
Examples: oxytocin, vasopressin
Overlap between romantic and maternal love activation patterns in brain?
Compared the neural circuitry underlying both types of love
Adults shown pictures of loved ones and pictures of people they know while in fMRI scanner.
Mothers were shown pictures of their babies or other infants.
Found overlapping areas of brain activation including the Basal Ganglia, as well as the Medial Insular and Anterior Cingulate Cortex.
Emphasizes that affiliative behaviors likely evolved from parental behaviors.
Brain regions with the most activation either are part of the brain’s reward circuitry (mesolimbic DA—ventral tegmental area, nucleus accumbens) or contain a high density of oxytocin & vasopressin receptors.
the brain’s reward circuitry
mesolimbic DA
ventral tegmental area
nucleus accumbens
Social bonding:
Partner preference
Prairie voles form partner preferences and long-term bonds
Social preferences can be determined in the 3-chamber preference apparatus
Partner preference is stable
Social bonding and partner preference not the same as sexual monogamy
Hormones underlying social affiliation:
Oxytocin (OT)
Using autoradiography the oxytocin receptor of monogamous and polygamous voles have been characterized.
Species difference also true for vasopressin V1aR too
Prairie Voles
Monogamous
Long-Lasting Pair Bonds
Pair bond doesn’t form if OT receptor blocked.
Lower circulating testosterone concentrations
Lower sperm numbers
Smaller testes
Meadow and Montane Voles
Polygamous
Higher circulating testosterone concentrations
Higher sperm numbers
Larger testes
Hormones underlying social affiliation:
Testosterone
Correlations between blood T concentrations and testis size, sperm counts, and social affiliation
(monogamy vs polygamy)
Lower T could indirectly mediate approach behaviors needed to care for offspring.
Hormones that evoke affiliation thus serve as a means of bringing about this cooperation.
Supplemental T to a monogamous vole will not induce promiscuity, just as castration of a polygamous vole will not induce monogamy.
_____ is more important in pair bond formation in females
Endogenous Oxytocin is more important in pair bond formation in females
_____ is more important for males
Endogenous AVP is more important for males
Oxytocin has role too
Yet distribution of receptors is same in males and females
Pair bond formation is rewarding
PreFrontal Cortex, Nucleus Accumbens (NA), VP —> reward and pair bond circuitry
Other hormones and factors that influence partner preference
Endogenous OT is more important in pair bond formation in females
Endogenous AVP is more important for males, though OT has role too
Yet distribution of receptors is same in males and females
PFC, NA, VP- reward and pair bond circuitry
Pair bond formation is rewarding
Opiod system.
Endogenous opiod antagonism prevents partner preference
Pair bond leads to increase in Dopamine and dopamine receptors in Nucleus Accumbens
Mating in prairie voles increases Dopamine turnover in reward system
Pair bonding also increases Dopamine receptor D1
Dopamine acting on D2 receptors in Nucleus accumbens leads to formation of pair bond following sexual encounter with new partner
Pair bond formation is rewarding
D1
Pair bonding increases Dopamine receptor D1
D1 receptor has no effect on initial formation, but a role in maintenance of social bond
D1 receptors mediate aggression toward stranger to solidify pair bond with partner
After bonded, D1 receptor increases linked to aggression towards stranger females.
Bonded males will prefer partner and attack stranger female. D1 antagonist blocks attacking stranger, D2 has no effect.
Meadow voles (the polygamous ones) have higher D1 receptor expression than prairie voles. Antagonizing D1 in meadow voles also increases time spent with females.
D2
Dopamine acting on D2 receptors in Nucleus Accumbens leads to formation of pair bond following sexual encounter with new partner
No affect on aggression
Involved in making a meadow vole monogamous.
Making a meadow vole monogamous?
Overexpress V1aR receptor in nucleus accumbens (ventral pallidum) of meadow voles
Partner preference can be induced
Also D2 dependent
Oxytocin and social monogamy in humans:
Heterosexual men self-described as “passionately in love”
Effect of oxytocin on reward system activation (fMRI) while viewing pictures of partner or attractiveness and feature matched stranger
Both ventral tegmental area (VTA) and nucleus accumbens (NA) show greater activation to partner than unfamiliar if OXY given 1st
Oxytocin Modulates Social Distance Between Males and Females
Participant asked to choose ideal distance to stand from an attractive female experimenter (in some, had to advance (far), in others had to retreat (close)
Oxytocin increased ‘ideal’ distance between male participant and female experimenter in men in a relationship
Single men showed no effect of oxytocin to increase social distance
No effects of oxytocin when experimenter was male (heterosexual subjects)
Oxytocin and autism
Oxytocin receptor polymorphisms seen in some autistic individuals, no difference in oxytocin levels overall.
Intranasal oxytocin can increase ‘empathy’ related brain activation, eye contact, and perception of social cues in high functioning autistic individuals
Oxytocin increases salience of social cues
Still unclear if intranasal oxytocin gets into brain
Clinical trials underway; concern about chronic treatment during development
Human-dog affiliative behavior and Oxytocin
Measure dog-owner interactions
Dogs that gaze more at their owners show higher Oxytocin following a 30min interaction, as do their owners
Not so in hand-raised wolves, where eye contact is aggressive or threatening to prey
Aggression
Social behavior that keeps animals apart
Overt behavior with intention of inflicting damage or unpleasantness on another
Superficially, the opposite of affiliation
Mediated by partially distinct circuits rather than differential activity of the same neurons
Types of aggression
Conflicts over limited resources such as territories, food, and mates arise
Each type has a different physiological cause and is expressed in different environmental and social context
A social interaction decides which animal gains access to the resource.
Gains can be substantial, but costs as well, even for ‘winner’…
Maternal, inter-male, territorial, sex-related, rank-related are all mediated by hormones
Some are evoked in the lab: irritable aggression (restraint), fear-induced (shock), resident-intruder tests
Costs of aggression
Tradeoff between time & resources spent on aggression/winning, and time & resources spent on foraging, hunting, immune function etc.
Hormones, season and aggression:
Red deer
Red Deer- live peacefully most of the time, in late summer antlers come into “hard horn”
Move to grassy areas and fight for control of the areas in early fall
Fierce battles, inflict damage
Social rank is based on ability to win the battles and oldest males are most experience fighters
After rutting season, shed antlers, aggression is reduced, go back to their bachelor groups
Seasonal changes in aggression
At the end of the summer, T levels increase and peak in mid autumn, the rising androgen levels are accompanied by antler growth, and aggressive behavior.
Mating occurs for about 2 weeks in mid autumn.
After mating, Testosterone levels diminish, aggressive behaviors wane, and males engage in few agonistic interactions.
Hormones and aggression in Red deer
New, soft antlers develop in High Testosterone levels destroy the velvet and it sheds at the end of summer
Low levels of Testosterone in winter cause stags to cast their antlers
Castration mimics reduction in testosterone and cause males to shed their antlers prematurely and thus plummet in rank
What happens if implanted with slow release testosterone capsules either in winter or summer?
Winter:
retained antlers due to constant supply of Testosterone, more aggressive, climbed in social rank
Summer:
climb in social rank even before antler development, aggressive before “weapon”
Mating still occurred during the appropriate autumn breeding season, suggesting that the estrous females generate a cue that stimulates the mating behavior.
Steroid hormones act on the brain to promote aggressiveness and act on the antler- the effectors of aggressive behavior
Aggression in rodents
Territorial during breeding season, social & interactive during winter
At the end of breeding season undergo reproductive regression due to lower concentrations of androgens
Breeding season: control resources, promote survival of themselves & offspring, defend resources
Winter: group living, conserve energy, enhance survival. Reduction in aggression allows this.
Some male rodents don’t undergo reproductive regression.
Advantages? Disadvantages?
They maintain testicular function and produce sperm & androgens during winter conditions.
High behavioral and energetic costs.
Capable of continuous breeding
Superior in fitness
May remain too aggressive during the winter to benefit from communal huddling
Give up energy savings
In many species, inter-male aggression rises during the breeding season that parallels the rise in Testosterone.
Activational —>
castration reduces, T replacement reinstates
Too much or too little testosterone has fitness costs
Seasonal changes in aggression in primates
Inter-male aggression during breeding season (i.e. lemurs & monkeys)
Human males:
Peak incidences of crime in North America are associated with high temperatures and peak androgen concentrations
Increased aggression for prisoners in a Maryland prison during the summer
Increased abuse reported by women in the U.S. during summer
Puberty
Testes grow larger
Increased amounts of androgens are secreted into the circulatory system
Increased reports of aggression- specifically inter-male and isolation-induced aggression are first observed at this time
Aggression often peaks at puberty, often actually decline into adulthood
Is it adaptive to have increased aggression during puberty?
Males of many rodent species disperse during this time, putting them in dangerous situations (encroaching on other males’ territories, competing for food, mates, etc.)
They have evolved to be aggressive to increase their odds of survival
Aggression often peaks at puberty and declines once adulthood reached
Aggression in primates
Dispersal also occurs in primates during puberty, and young male rhesus monkeys become the target of adult aggressive behaviors, and must find a new group to join
Either burst into a new group, or hang in the periphery until the right time and sneak in!
Bursting into a new group could come with resistance and aggression towards the newcomer, but sneaking in also has disadvantages- could starve or succumb to illness.
What strategy to choose?
Sons of a high ranking females tend to be outgoing, venture far from mother, low autonomic reactivity, low cortisol concentrations.
They tend to burst in.
Son of a low ranking female have high autonomic activity, high cortisol levels (experience more stress).
Early life stress exposure can decide these things for emergent adults.
Sex differences in aggression
Overall, males are more aggressive than females
Sex differences appear at a very early age
Why are there differences?
Males have higher concentrations of circulating androgens
Males are exposed to androgens prenatally, wiring of brain therefore facilitates aggression
Boys are encouraged, girls discouraged
Male mice castrated before PD6 treated with Testosterone during adulthood
Low levels of Aggression
ORGANIZATIONAL!!!
Females ovariectomized before PD6 treated with Androgens in adulthood
Little to no Aggression
Gonadectomized male or female treated with Testosterone perinatally prior to PD6, AND in adulthood
Typical levels of aggression seen in normal males
IS the sex difference in aggression due to higher adult blood concentrations of androgens in males than in females, or are males more aggressive than females because their brains are organized differently by perinatal hormones?
So what does these result mean?
Aggression is organized perinatally by androgens but also requires the presence of androgens after puberty in order to be fully expressed.
Proclivity to act more aggressive (in males) is organized perinatally by androgens but also requires the presence of androgens after puberty in order to be fully expressed
Experience with social behaviors influence hormones:
Winning
Behavior can feed back and affect hormone concentrations
Social defeat in many species is correlated with a reduction in levels of circulating androgens for many days after!!
Winning increases circulating androgens in males for the following 24h
True in humans too.... Home vs away: higher T before home games Challenging team: if hard opponent, higher Testosterone before game, esp. in goalies
Just before a home game, testosterone levels in soccer players are higher than in away games.
Testosterone levels are also higher before playing against a challenging team than a moderate one.
Fans:
2002- osu beats michigan and had a perfect season —> riots started, couches burned
Winning:
California mice
Winning a fight increases the male mice subsequent motivation to fight and enhances the ability to win- only if the previous winning experience was in his home cage
winning on one’s own turf potentiates further aggression.
Winning in a place that’s familiar/important to you must be a factor.
Winner Effect
mediated by androgens and associated with an up-regulation of androgen receptors in brain areas involved in reward, ventral tegmental area (VTA) and nucleus accumbens (NA).
Giving testosterone is more effective at increasing aggression in subsequent conflicts if paired with a winning conflict (testosterone following win)
…
Conditioned Social Defeat
CSD
Refers to losing a confrontation
Defeat of Syrian hamster in the home cage leads to failure to defend their own home territory even if the new intruder is smaller
Evokes stress response: elevated HPA activity, ACTH, CORT and decreased T and prolactin
Physiological and behavioral responses can last up to 33d and maybe through adulthood
Few female hamsters exhibit CSD, display low levels of submissive or defensive behaviors, results only last through the first test.
Strong sex difference.
CSD in males is a profound and persistent behavioral change
