9th September 2005 at 01:00
Visual psychologists love illusions, because they provide a means of understanding how the brain and the visual system interact. Here are a few well known ones.

The size of the surrounding circles affects our perception of the size of the centre circle

Another disruption of our perception of parallel lines: this time by horizontal and vertical interference

We tend to fill in the contours of the illusory triangle, rather than completing the circles

Muller-Lyer illusion: most people see the vertical line on the left as longer than the one on the right

More illusions can be found at http:\\

Log-in as an existing print or digital subscriber

Forgotten your subscriber ID?


To access this content and the full TES archive, subscribe now.

View subscriber offers


Get TES online and delivered to your door – for less than the price of a coffee

Save 33% off the cover price with this great subscription offer. Every copy delivered to your door by first-class post, plus full access to TES online and the TES app for just £1.90 per week.
Subscribers also enjoy a range of fantastic offers and benefits worth over £270:

  • Discounts off TES Institute courses
  • Access over 200,000 articles in the TES online archive
  • Free Tastecard membership worth £79.99
  • Discounts with Zipcar,, Virgin Wines and other partners
Order your low-cost subscription today