Your attractiveness may be down to how you smell

We already know that imprinting is a crucial psychological mechanism for young animals to identify their parents. It’s why a group of ducklings will follow their mother, rather than some random duck that happens to be in the area. The biological reasons for this process, however, have been largely mysterious.

A study published in Neuron from the University of California San Diego attempts to shine some light on the cellular-level intricacies of family attachment. Over the course of eight years, a team of researchers, split between the university’s psychiatry department and the division of biological sciences, studied the neurobiology of tadpoles. What they found was a complex “switch” between different neurotransmitters.

Tadpoles are known to swim with family members in clusters. Tests by the scientists revealed this has a lot to do with specific olfactory cues; odours that are associated with kinship. They noticed that two- to four-day old tadpoles exposed to family members would tend to swim with them. If exposed to non-kin during these early formative days, they would also be inclined to swim with the group that generated the smell.

However, the researchers found that a process known as “neurotransmitter switching” happens between kin and non-kin bonds. When bonding with family members, the tadpole brains’ had high levels of the dopamine neurotransmitter. When bonding with non-kin tadpole, their brains switched to the GABA neurotransmitter.

“In the reversed conditions there is a clear sign of neurotransmitter switching, so now we can see that these neurotransmitters are really controlling a specific behaviour,” said Dulcis, an associate professor at UC San Diego.

“You can imagine how important this is for social preference and behavior. We have innate responses in relationships, falling in love and deciding whether we like someone. We use a variety of cues and these odorants can be part of the social preference equation.”

(Above: An image of a tadpole brain. Dopaminergic neurons are coloured green, and GABAergic neurons are coloured red. Credit: UC San Diego)

Further investigation at a genetic level led the scientists to isolate two microRNAs as being responsible for mediating the gene expression of different types of attraction (microRNA-375 and microRNA-200b, to be precise). These microRNAs affect the expression of the genes Pax6 and Bcl11b, which in turn dictate the Tadpole’s swimming behaviour.

There are many different factors that dictate how we interact with family members, or lovers, or friends, or co-workers, or household plants. While this latest study doesn’t quite offer a one-size-fits-all smell-based solution to attraction, one of the study’s authors and co-director of the Kavli Institute for Brain and Mind at UC San Diego – Nick Spitzer – suggested neurotransmitter switching could be crucial part of how was build social bonds.  

“Social interaction, whether it’s with people in the workplace or with family and friends, has many determinants,” said Spitzer. “As human beings we are complicated and we have multiple mechanisms to achieve social bonding, but it seems likely that this mechanism for switching social preference in response to olfactory stimuli contributes to some extent.”