Who would think that beneath that calm exterior there is a boiling mass of emotions? I'm not talking about Wimbledon champions here, but cows. Yes, cows; those creatures that we eat, and take milk from, but rarely think about. According to new research by scientists at Northampton University, cows have "best friends" and get stressed when separated.

In his book The Cow, the former butcher and poet Beat Sterchi invented an adjective to describe the way that cows stand placidly – "cowpeaceably". If you watch cows lying down in a field they will normally be ruminating (chewing on regurgitated grass), staring blankly into space and looking totally at peace. This state of total calmness makes the cow appear withdrawn and "otherworldly". This is perhaps why we assume there is nothing much going on between a cow's ears.

But we cow lovers have always known that cows have emotional depth. DH Lawrence wrote brilliantly about his relationship with Susan, a black cow that he milked every morning in 1924-5 on his ranch in Taos, New Mexico. He comments on her "cowy oblivion", her "cow inertia", her "cowy passivity" and her "cowy peace" and he wonders where she goes to in her trances. But he believes, quite rightly, that there is always "a certain untouched chaos in her", which is never far away. Some days, he writes, she is "fractious, tiresome, and a faggot". This is because she will deliberately do things to annoy him, such as swinging her tail in his face during milking: "So sometimes she swings it, just on purpose: and looks at me out of the black corner of her great, pure-black eye, when I yell at her."

To anyone who works, or has worked, with cows, it comes as no surprise that cows are capable of friendships. Within any herd there is a pecking order that results in cows coming into the milking parlour every time in more or less the same position in the queue. At the dairy farm I worked on as an agricultural student we had "Devilish Delilah", "Crafty Caroline" and "Pain-In-The-Arse Mary-Rose" – all of which were nicknamed because of their annoying or aggressive antics at milking time or feeding time. Dominant cows will push their way to the front of the queue, bully and intimidate more sensitive souls, and dictate when and where the group will move around their pasture. No submissive cow would want to be their "best friend".

Certain cows will always be the ring leaders when trouble occurs – bulldozing fences until they give way is often found out by accident, but then pursued with great joy by the felons. And woe betide anyone who gets in the way of a protective mother and her calf; she'll knock you for six and reverse over you for good measure.

But there are also the gentler cows who always appreciate a scratch behind the ear as you go past and the cows that Temple Grandin, the animal scientist, would describe as "curiously afraid". These cows, and most do exhibit this behaviour, will be curious of any new thing but terrified of it at the same time. The braver ones will come forward to investigate first, but will stand at such a distance that their necks and tongues will be stretched out as far as possible so they don't have to be too close. They will snort, sniff and try to lick the novelty until they decide after about 15 minutes that they are bored and will wander off. There's a lot going on between those hairy ears.