Our research found that when the father mouse is removed from the litter after the birth of the pups, the young mice grow up socially impaired.
From the time of Sigmund Freud and continuing through the development of the Bowlby-Ainsworth attachment theory until today, the mother figure has attracted more attention than that of the father in childhood development. In fact, the role of the father has been highly neglected in psychology and—especially—in neuroscience. My research has tried to fill this gap.
Californian (Peromyscus californicus) mice are a species very similar to humans for parenting behavior: mothers and fathers form a permanent bond and both are involved in raising the pups (huddling, licking, grooming, carrying, etc.). For this reason, this species is considered a good model to study the consequences of father absence in a laboratory setting.
Our research found that when the father mouse is removed from the litter after the birth of the pups, the young mice grow up socially impaired. We also found that parts of their brains associated with social interaction were different.
We permanently removed fathers from one group of litters and left the fathers in another group of litters. Then, when pups become adult, we tested them with different situations to understand their behaviour. We first paired them, male-male and female-female, and monitored their interactions. We found big differences when one or both of the mice in these pairs was “paternally deprived” (PD).
When two PD males are put together, there is a dramatic reduction in social investigation (sniffing, trailing, crawling over) and they are more “socially anxious” during the approach. This effect disappears when one of the males had a father present.
Females showed even greater reductions in social behaviour and, furthermore, this reduced social behavior was evident even when only one of the two mice was paternally deprived.
Females, when exposed to amphetamines, were also more susceptible to their effects, meaning a stronger predisposition eventually to develop addictive behaviour.
We also conducted a range of brain tests, using electrophysiology, that is a technique allowing to record the electrical activity of each single neuron in the brain. We found changes in the medial prefrontal cortex of the brain, that is an area where cognitive, social and emotional behaviours are controlled. In particular in this area, the dopamine system that regulates emotional behaviour, additive behaviour and aggression, was impaired along with serotonin and glutamate transmission, implicated respectively in mood regulation and cognition.
We observed the two groups of litters, one group with fathers and one with, to see what differences there were. In paternally deprived litters there was less rough and tumble play. Perhaps this has a role in developing social competence.
Could it be that the issue is not the absence of the father but the increased stress of the mother without the father present? But we saw no change in the mother’s behaviour in paternally deprived litters. Indeed, she did not increase her care at all in the absence of the father.
Even if human beings are, of course, more complex than humans, these experiments in a controlled setting, allowed us to confirm that changes in mice are similar to the effects of paternal deprivation previously observed in human children, namely less social behaviour, less intellectual and linguistic competence, fewer relationship skills and increased risk of addiction for girls.