Your research shows that a man's brain

shrinks when he becomes a father.

>> Yes. In fathers, the brain is actually

losing gray matter volume. The parts of

the brain that are shrinking the most

are in what we call the mentalizing

network. And that's a part of the brain

that helps us understand other people's

feelings and intentions. And then you

also see volume reduction in the visual

areas, which is the back of the brain,

which is really important for

understanding when you look at an

infant's face what kinds of emotions

it's trying to tell you. Dads are mostly

changing in this top layer, the cortex,

which kind of controls our higher-order

thinking, reasoning, and executive

functioning.

>> The way that you described the part of

the brain that the man loses when they

become a father made it seem like

they're losing empathy.

>> No, they're actually improving in their

empathy because they're becoming more

efficient processors of social

information. So, the fact that where we

see the biggest changes are in these

what we call mentalizing social

cognition networks tells us that those

networks are really important for dads

to use when they become parents.

>> I thought you said that section of the

brain shrunk.

>> Yes, because the brain is becoming more

efficient.

>> Oh.

>> It's losing all the extra pathways and

you're sort of building a superhighway

for that specific social information.

>> Sounds a bit counterintuitive cuz I

imagine that my brain would grow when I

get better at something.

>> In this case, the brain is actually

shrinking. And I know it it sort of

feels like a puzzle to wrap your head

around, but it actually does reflect

that the brain is working better. And

it's working faster because you're sort

of clearing the debris and you're just

streamlined in how you're processing

information.

>> Is there a relationship between how

hands-on the father is and the amount of

shrinkage that happens in their brain?

>> Yeah, and my lab found that

relationship. So, when dads told us

before birth that they felt more bonded

to their unborn baby, when they wanted

to take more time off, and when they

told us 3 months after birth that they

enjoyed their babies more, they felt

more connected and bonded to them, and

they were spending more time taking care

of their babies, they had more profound

brain shrinkage. All of this seems to

support the contention that the

shrinkage is really adaptive, and it's

enabling men's adjustment to parenthood.