They discovered that when people are offered an unfair split, a primal part of their brains known as the anterior insula sends out signals of disgust and anger.

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The reason for this, the UCLA life scientists found, seems to be that a brain region called the anterior insula, which is linked to disgust and is important for discerning untrustworthy faces, is less active in older adults.

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Interestingly, however, when people with hoarding disorder made similar decisions about discarding junk mail that didn't belong to them, they again showed unusual levels of activity in the anterior cingulate cortex and insula but in this case, their brain activity was much lower than normal.

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