Abbey street is busy on a chilly autumn afternoon and the two euro shop is selling its last pair of fairy wings. A little girl waits for a luas. She is standing alone and dressed in a wine-coloured pinafore. She has an enormous pair of hazel eyes and a face entirely covered with freckles. There’s an incongruence in her features that is really beautiful. I’m thinking that she should play the lead role in a French art-house movie, when she sees me looking and says ‘What the fuck are you looking at you fucking bitch?’

I am so taken aback that I turn and walk away but I sense her youthful venom following me. She’s about eight.

A few weeks later I’m at the bus stop opposite my house when the hooded figure of a man pulling a bin bag shuffles towards me. It’s dark and the street is quiet. Instinct prevails. I move away to the corner of the road pretending I am looking out for taxis. His eyes are fixed on me. I can feel it. The two pedestrians I was counting on have passed on by. I fumble for my keys. He’s on to me. I make to cross the road and he erupts, calling after me in language he learnt from the lead role in an art house movie. I don’t excuse his French. I rush up my steps and let myself in, missing the bus that he is too drunk to hail.

I wasn’t always like this. Once I was walking along the canal coming up to Ranelagh and four cider-drinking, tracky-clad boys were having a laugh. Few cans, a bit of banter – a little mock fighting: nothing serious. I forced myself not to cross the road. After all, it was a summer’s afternoon in a leafy suburb and I was at one with the world. I strolled by, listening happily to my sunny- day music when two of them pounced out at me, blocking my way and pulling at the cord of my earphones  ‘Oy gissus yer oipod will ya?’, they laughed as I dodged under their arms. They released the earphones and guffawed at my reaction. Scurrying away sheepishly, I conceded that I almost deserved their farcical affront. Almost. They had smelt out my political correctness.

Sensory perception is an enormous area of research in psychology. They’ve labelled the occipital lobe, explored haptic contact, identified the primary auditory cortex, stimulated the taste buds and developed expensive machinery to produce odours. When it comes to how we see into ourselves, smell out dangerous people, touch on a delicate issue and describe those around us as having ‘taste’ however, the issue becomes blurred and resistant to empirical research.

Social perceptions are in the way we speak, look, move, socialise, perceive and educate. It’s hoopy earrings, whether your money comes from your builder dad or your doctor mum, luminous boob tubes, gym membership, your use of the habitual present tense and whether Lillie’s Bordello makes you puke before or after your visit. It is so blatant that it achieves subtlety in mature discourse. It is ingrained and chemically mapped. It is a system of immediate classification that occurs largely unconsciously. It’s what conjured up images of an abusive family life in a small and dirty flat when the little angel girl spat venom. It’s what makes me want and not want to cross roads.

Lawyers can become experts in questions of boundaries, engineers can construct bridges and teachers can convey principles of respect. Neuroscientists can breed impulsive rodents, geneticists can link genes to personality traits and social psychologists can construct an ABC model of attitude. Somewhere along the way we all know to learn or learn to know not to look everybody in the eye.