Social recognition depends on our sense of smell. It’s been known for some time that a part of the brain called the olfactory bulb (OB) plays a part in social recognition—our ability to recognize people we know. In this we are the same as almost all mammals. However the exact mechanism of this wasn’t known. Now a study, published in the latest edition of the journalBiological Psychiatry gives some clarity to this and some interesting titbits on depression and neurochemicals: oxytocin. Apparently what happens is that when we meet someone their scent is decoded by the OB and sent to the amygdala—the fear and protection hub of the brain. The amygdala decides whether the scent is of someone we like or dislike. If we like the person we get a shot of oxytocin—the bonding chemical—triggering recognition and all is well. If there is something faulty with the OB or the oxytocin system we get stressed and we don’t make the connection. If this goes on for any length of time we become depressed. I can’t help wondering if the burgeoning use of perfumes and deodorants (in both men and women) might be responsible in part for our increasing social isolation and the rise in the depression rate. It also explains, to some extent, why emails are linked to both stress and depression. Genetically we are geared for face-to-face communication where all the senses can be used to judge safety, trust and the like. Take that sensory experience away and things begin to go wrong.