Ah, true love. Who can quantify that heady rush, the joy of another’s company, the unshakable bonds between one lover and another? Well, vole experts can.

This tiny rodent is not just an anagram of love, it can also teach us a lot about why we fall. And why we sometimes stray. Prairie Voles form lifelong monogamous bonds, together until death they do part. Almost identical Meadow Voles don’t, living the single life, and mating at will. It all comes down to brain chemistry. And it turns out, some of us are more Prairie Vole than others.

Featuring Dr Larry Young from Emory University, and author of 'Sex at Dawn', Chris Ryan.