You don't always have to be thinking saucy thoughts to get sexually turned on. Here are some common trouser arouser triggers:

First thing in the morning

Sometimes your old fella can take on a life of it's own, often from the moment you wake up. The stiffy you find as you stir from sleep is generally known as a 'morning glory'. It doesn't mean you've been dreaming about sex - it's simply a result of changes in your brain pattern while you're snoring. It can occur several times in the night, in fact. It's just you'll only be aware of the one you wake up with. They're perfectly harmless, however, and will quickly power down without a helping hand from you - that is, if you choose to leave it alone.

On the bus

So there you are, sitting by the window at a red light. There's nothing remotely sexy about your fellow passengers - and the old lady beside you smells of wee and bleach. Which is why you're so freaked out by the hard on currently causing havoc in your pants. What's going on here? Does it mean you're some kind of bus freak? No. It's simply something to do with the throb and hum of the engine - often your dick picks up on physical sensations that you don't consciously notice. So leave it alone, and nobody will pay it any attention so long as you don't make a big song and dance about it.

In the pool

Why oh why does this happen? We don't know, but it can be hugely embarrassing and not easy to cover up, particularly if you've been parading around in skimpy Speedos (although there's a lesson in there somewhere). That's why you need to keep in the water if you want to stay out of trouble with the pool attendant, and aim to occupy your mind with non-sexual thoughts such as knitting, arithmetic and jigsaw puzzles - it'll calm down in no time. Otherwise, burn off the tension by doing some lengths, so to speak - anything but backstroke.

Is that a penis in your pocket?

Yes, it can happen - there's always a chance that your unwanted state of excitement is spotted and suddenly you're left facing questions that are one part amusement and two parts alarm. The key is not to defend your dick, (especially if it hasn't been charged by idle fantasies, but the position in which you've been sitting). Instead, just see it for what it is, a physical stirring that has no bearing on what you're thinking. Chances are the attention you're getting will see your soldier stand down pretty quickly, so there's no need to run for cover or throw yourself onto your front until it goes - not in a busy street, at least.

What else is normal?

• Getting hard-ons for no reason: Blame your hormones, sit down, and put a jumper on your lap.
• Not getting one during a sexy situation: When you're feeling shy or anxious, it's a passion killer. And yes, it does happen to just about everyone sooner or later.
• An erection that bends a bit to the side: If it has always been like that, it just means that one of the chambers inside the penis is slightly larger than the other.
• The angle of a man's erection changing as he gets older: It can go from almost vertical to horizontal, and still work perfectly well.

What isn't normal?

Priapism: An erection, nearly always painful, that won't go away. The mechanism that allows blood to flow out of the penis is damaged, possibly due to surgery, trauma, drugs, alcohol abuse or blood disorders. If it doesn't subside, bite the bullet and get down to your GP or Accident and Emergency. They will be able to give

Peyronie's disease: This begins in adolescent or older men, and can produce tender lumps in the penis, or sharp bends in it during erection, and sometimes pain in the shaft. It's due to the formation of tough fibrous plaques, but the cause is not certain (it may be due to injury or genetic predisposition). It may be something the sufferer can live with, and often does not get any worse. If the condition worsens, there are several treatments that include drugs, localised shockwave therapy, or surgery (in extreme cases only).

Updated: 17/01/2007