A group of Swedish researchers have discovered why humans get goose bumps and nipples get erect regardless of the physical or emotional trigger.

According to Metro.co.uk, the researchers found out new information about the sympathetic nerve system, which is behind the involuntary reactions that have baffled scientists.

Previously, it was thought that the cells respond in the same way as others in the body, regardless of the physical or emotional trigger.

It is effectively beyond our control, and has long been considered to produce the same response – no matter what type of physical or emotional cause stimulates it.

Earlier research had not been able to definitively show that different cell types would have different functions.

For this study, the researchers carried out a large-scale analysis of sympathetic nerve cells, from which they were able to show that there are several different types of sympathetic neurons and they are associated with different functions.

Study lead author Doctor Alessandro Furlan said: “We’ve shown that the sympathetic system consists of many types of neuron that regulate specific functions in the body.

“For example, one thing we found was that goose bumps and nipple erection are caused by neurons that are specialised to regulate these functions by controlling the erectile muscles in these tissues.”