Sometimes you meet somebody new and instantly click with them.
This feeling of being on the same wavelength as another person is now a measurable scientific phenomenon known as brain coupling.
The idea that like-minded people prefer to spend time with each other is not a new one and the proverb 'birds of a feather flock together' has been around since the 16th century.
Previous research around friendship formation has shown that people tend to naturally prefer to develop relationships with individuals of a similar age, gender and ethnicity.
Now science shows that close friendships run much deeper than originally thought with the brainwaves of friends matching so closely that brain scanners can be used to predict how close friendships are.
The study published in the journal Nature Communications scanned the brains of 42 students using a functional magnetic resonance imaging (fMRI) scanner.
As an electrochemical organ, the brain can generate as much as 10 watts of electrical power, through brainwaves which are produced by electrical pulses from communicating neurons.
These neurons lie at the root of all of our thoughts, behaviours and emotions and measuring the electrical activity from these brainwaves can give insights into how stimulated an individual is at any point in time.
The fMRI scanner can identify which parts of the brain are more active by measuring changes in blood flow.
The more blood flow needed, the more oxygen that region of the brain is consuming, indicating that there is more brain activity in that area.
In the study, the students were asked to watch over half an hour of short videos which included music videos, documentaries and comedies designed to evoke a range of emotional responses in the individuals.
While the volunteers watched the content, 80 separate anatomical regions of their brains were scanned to measure how the different content was interpreted by each area of the brain.
The results showed striking neural similarity between the brains of people who were close friends and much less similarity between two people who classed themselves as acquaintances.
The research showed the concept of neural homophily or the idea that people tend to be friends with those who see the world in a similar way to them.
So accurate was the brain data that the researchers could accurately identify if two people in the study were friends, acquaintances or complete strangers just by using the information from their brain scans.
What the study wasn't able to identify was whether people tend to make friends with individuals who see the world in a similar way to them, or if friendships evolve over time so that both individuals start to see the world in a similar way together.
These new findings add to a growing field of research showing that people's brains can connect in a social context and respond similarly when friends tell stories to each other or when they watch a film together.
The concept that brain coupling allows two individuals to feel a single, shared emotion can also progress to physical attributes over time with close friends showing similar body gestures and facial expressions as they start to mirror each other.
Although still in its infancy, the idea around individuals sharing similar brain waves and being able to emotionally connect in the same way has huge potential for educators and communicators to be able to increase engagement with those who are listening to them.
The next time you catch yourself saying 'great minds think alike' remember it's no longer just a figure of speech, but now a proven, validated phenomenon in neuroscience.
Dr Michelle Dickinson, also known as Nanogirl, is an Auckland University nanotechnologist who is passionate about getting Kiwis hooked on science. Tweet her your science questions @medickinson