Fill your glass - and your wallet - with this perfect-for-the-bar trick

Then measure the height. Even with a boost from cellphones and notebooks, the rim's circumference...

Then measure the height. Even with a boost from cellphones and notebooks, the rim's circumference is bigger than the height of the glass. (Supplied)

Maila Rible, QMI AGENCY

, Last Updated: 9:42 AM ET

Most people are pretty confident they can believe what they see. But those willing to tear a page out of the illusionists' playbook, and channel their inner pitchman, can set themselves up nicely for some fun and profit.

If you're unsure of your ability to bluff your way through a bar bet, just remember: Science is on your side!

Start by identifying your mark. Maybe your friend owes you some cash, maybe you just want to take the dude wearing sunglasses at midnight down a peg or two.

Saunter up with a pint glass and plunk it down on the table. Ask him which he thinks is longer: The height of the pint glass or the distance around the rim (that would be the circumference, but keep it simple for the time being unless geek is part of your schtick).

If the guy says the height of the glass is the longer distance, ask him if he's willing to put his money where his mouth is. If the bet's on, you have a lot less work to do. Most people's first observational inclination is that the glass’ height is greater than its circumference. But if you've made a bet, they probably know you're up to something and will change their mind. Now it's time for the sell.

Grab something like a cell phone and place it under the bottom of the glass. Is the rim still greater than the height? Add a deck of playing cards. What about now? Stack up more handy stuff: A pack of cigarettes, a note pad, a business card holder.

While you're upping the height of the glass, up the ante as well. By the time you start closing in on 7 or 8 cm of extra height, chances are your mark will be sweating.

To determine the winner, grab something like a paper napkin, unfold it and use it as your measuring tape. First, wrap it around the glass, pinching the spot where the ends meet. Keep your fingers exactly where you left them and hold the napkin up to measure the height. Even on top of the pile, the glass is still shorter than the distance around the rim.

There is no sleight-of-hand here; the distance around the rim really is way longer than the height. So why is it so difficult to see?

Blame the human brain. We evolved to build a picture about the world around us and build that picture quickly. We also have certain innate expectations about what we see.

Since we can't easily compare the distance around the rim of the glass with the height, our brains make a judgment call. Too bad for your mark it's a costly one.

You'll be surprised just how much stuff you can pile up before the two distances equalize. Just be sure to practice ahead of time. One too many cellphones and you'll be paying up instead.

What You'll Need:

  • Pint glass
  • Things to stack under glass (cellphone, card deck, etc.)
  • Paper napkin
  • Fast talk

For more fun optical illusions, check out:

- llusions.org

- moillusions.com

- games.yahoo.com/brain-games/brain-teasers


Photos