When on a strict diet, it can be very hard to resist a bar of chocolate if it is right under your nose. Are you likely to eat it there and then? Or wait until the end of the week to intensify the satisfying experience? Whatever your answer, researchers now say they can explain the difference in people's ability to resist temptation.
According to researchers from the Brain and Spine Institute in Paris, activity in the hippocampus of the brain - an area of the brain involved in forming, storing and organizing memories - is crucial in making the decision to delay rewards.
Previous studies have analyzed human's temporal choices, with researchers conducting brain scans while participants are asked to make monetary choices, such as $10 now or $11 tomorrow.
"However, these paradigms miss an essential feature of the inter-temporal conflicts we have to face in everyday life," says Dr. Mathias Pessiglione of the Brain and Spine Institute and leader of the study.
"[...] immediate rewards can be perceived through our senses, whereas future rewards must be represented in our imagination."
To reach their findings, published in the journal PLOS Biology, the researchers conducted a series of experiments on volunteers using more natural rewards that people come across in everyday life. For example, participants were asked if they would like a beer today, or a bottle of champagne in a week's time.
Imagining future rewards
The participants were presented with choices between immediate rewards that were presented as pictures, or future rewards that were presented as text, meaning participants had to "imagine" the long-term rewards.
The researchers found that the ability to select future rewards was linked to the amount of activity in the hippocampus.
They then conducted the same experiments on a group of patients with hippocampus damage as a result of Alzheimer's disease, alongside patients with behavioral variant of frontotemporal dementia (bvFTD) as a result of prefrontal cortex degeneration. The prefrontal cortex of the brain is known to implement behavioral control.
Results showed that those with bvFTD demonstrated high impulsiveness in all choices, but those with Alzheimer's disease showed more bias towards immediate rewards when long-term rewards had to be imagined.
Dr. Pessiglione says the reason for these results is because the hippocampus plays an important role in imagining future situations by building details that makes long-term rewards appear more attractive.