But, in adolescence, a whole new set of impulses kick in, "from sex to drugs to rock and roll," Aber said. "There are a number of underlying biological changes with hormones and marketing consumption."
Now, with the advent of brain imaging, scientists know that the prefrontal cortex does not fully form until a person is in his or her mid-20s.
"The insurance actuarials learned that first," he said. "You have to be 25 to rent a car. It turns out, that's about the average age that structural part of the brain matures."
An adult is often fine for 20 or 30 years and then develops one of the degenerative conditions of aging and can lose self-regulation. Certain forms of drug use -- Parkinson's disease medications, for example -- can trigger gambling addictions. Brain lesions can also affect impulses.
Psychiatrist Kafka, who has not treated Weiner, said that those who exhibit repetitive impulse control problems -- "guys who look at porn, masturbate a lot and expose themselves" -- rather than a single incident, often have an underlying psychiatric disorder.
When these men eventually get to a psychiatrist, they are diagnosed with mood disorders, attention-deficit disorder (ADD) or have abused drugs or alcohol.
"Some people have low-grade depression," he said. "Others have spectrum bipolar disorder with brief hypomanic periods that last a day or two. During that time, they get revved up or impulsive and have a propensity for sex or spending money or not making good decisions."
Those with ADD can have "boredom intolerance," which is associated with risky behavior.
Weiner was adamant that he hasn't had a physical relationship outside of his marriage and some of his constituents have said they are less concerned about his sexting habits than his lies about them.
But Kafka said compulsive sex habits cannot be explained as just rogue behavior that somehow extends late into adulthood.
"I am sure someone may differ with me," Kafka said. "But I don't think it's just a personality thing. I always see it as pathology. ... Usually, it's a mistreated psychiatric disorder, not a character disorder."