GLASGOW buses can be pure theatre. Some trips are uneventful; others travel along a spectrum that arcs from generic freak show to something Samuel Beckett would have scripted on a good day. That’s why I like being on the bus. As a seasoned passenger, I’ve learned to take the good with the bad, the rough with the smooth. The other day, though, I was not sure whether it was good/bad/rough or indeed, harmless. That was the problem. I didn’t know.

To set the stage, I was ensconced in my preferred downstairs window seat with my newspaper (yes, some folk still actually buy one), rucksack on my lap and my rather large handbag occupying the seat beside me. The bus wasn’t busy so I didn’t feel too anti-social positioning my bag as a discreet, non-paying passenger. Near the city centre, a chap got on and, despite the abundance of available seats, sat beside me. I only glanced at him for a nano-second, yet I realised there was something strange about him. In the blink of an eye and with millions of years of evolution rushing to my aid, my brain rapidly alerted me to the fact he was just plain creepy. I was uneasy beside him and contemplated moving seats.

An internal dialogue raged along the lines of: "Just say excuse me and get off. Will I make him feel bad? Maybe he’ll get annoyed?" The more socialised part of my brain argued back: "Don’t be silly! It’ll seem rude. He’s not going to harm you …”

The fact was that I just didn’t know how to interpret the signals I was picking up from this guy. There was an ambiguity about his intent and ambiguity about the threat he did or indeed, didn’t pose. And he smelled bad.

Results of a recent international survey of 1,340 people published in the USA have given more insight into what we perceive as creepy.

According to this research, consistent markers include peculiar smile; bulging eyes; laughing at odd times; greasy/unkempt hair; displaying too much/little emotion; steering conversation toward one topic (especially sex); making you feel trapped; asking to take a picture of you; standing too close; lack of eye contact; too much eye contact. Men and women overwhelmingly reported that a typical creepy person is much more likely to be male.

The four most creepy occupations, in order, were: clown, taxidermist, sex shop owner and funeral director. Interestingly, the profession perceived as the least creepy was "meteorologist". The creepiest hobbies were activities that involved collecting things like dolls, insects or body parts such as teeth or fingernails and other activities that involved "watching" such as taking (unsolicited) pictures of people, children and even bird watching.

Many of the characteristics cited are not overtly threatening but people who display unusual patterns of non-verbal behaviour, odd emotional tics or distinctive physical markers are outside of the norm and, by definition, unpredictable. It is this very unpredictability that triggers our alarm. The creepiness comes from not knowing how a person is likely to behave towards us, particularly if they are saying one thing, but signalling something quite different by the way they look at us or via body language or appearance. This is what I experienced on the bus. I was getting conflicting signals about the reality of the threat the creepy guy posed for me. In this instance, ignoring my alarm didn’t result in harm. But for some people, ignoring their instinct about a person’s creepiness can be devastating. Think of Jimmy Savile.

Savile, probably this country’s most prolific paedophile and sex abuser of vulnerable women and men, was seen as creepy right from the start of his career as a DJ in the 1950s and 1960s. He was the embodiment of the dark triad of personality traits: narcissism, Machiavellianism and psychopathy. He managed to mask these traits as eccentricity, free-spiritedness and saintly blokeyness. He was an expert predator, targeting the most vulnerable. Over and over again, accounts given by those Savile abused, mention that he came across as creepy or weird. Like a rattlesnake, he would strike quickly, when his victims least expected it, under cover of his "idiosyncrasy". In the end, he was predictably unpredictable, abusing and violating whenever and wherever the notion took him.

Savile was king of creeps; his celebrity reign dazzled those around him into silence. How differently things might have turned out if those in authority and especially those responsible for protecting children and vulnerable persons, had not ignored their creep alert. Sometimes, it pays to take instinct seriously.