Millions of people suffer from addictions worldwide - whether from drugs, alcohol, tobacco, gambling, theft or any number of vices and the biology behind seeking endless gratification that damages your life has been of interest to scientists for years.

Researchers pinpointed two brain circuits used to make the calculations behind addictive or compulsive behavior, according to a new report published online Sunday in Nature Neuroscience.

The better we understand our decision-making brain circuitry, the better was can target treatment, whether it's pharmaceutical, behavioral or deep brain stimulation, said Jonathan Wallis, psychology and neuroscience professor at the University of California at Berkeley and lead author.

Previously, scientists knew the two brain regions, technically known as the orbitofrontal and anterior cingulate cortex, played a role in how people make decisions. When the two regions were damaged, patients became poor decision makers.

The research team used macaque monkeys to measure the brain regions as the test subjects played a game that included relating pictures to rewards of juice.

The monkeys quickly learned which pictures gave a juice treat while scientists monitored their brain activities.

The researchers were able to view which brain areas the monkeys used to calculate their decisions as the animals weighed the costs, benefits and risks of reward.

The researchers concluded that the orbitofrontal cortex allows the switch between important decisions such as whether to get married versus trivial decisions like which restaurant to take a date.

In the case of addicts, the neural activity did not change depending on the gravity of the situation.

In the other region, the anterior cingulate cortex, researchers found that the monkeys continued to make poor decisions and didn't learn from experience.

This is the first study to pin down the calculations made by these two specific parts of the brain that underlie healthy decision-making, Wallis said.