It's All in Your Head

In his first lecture, Bruce Hood showed how our brains represent the world around us, but reality doesn’t necessarily match up with what’s in our head.

Try out some of the illusions from the show - and some additional illusions that didn't make it into the lecture.

Freaky Finger

Get a friend to place their hand palm to palm with your hand. Gently stroke both hands at the same time using the thumb and forefinger of your free hand. Many people feel an eerie sense of having a dead finger.

Your brain takes the information from all our senses and fits it all together. When information from one sense (e.g. touch) doesn’t match that from another (e.g. vision) the brain will come up with an answer. Sometimes it’s the wrong answer and we experience an illusion. Psychologists are fascinated by these false realities as they provide clues into the inner workings of our mind.

The Vanishing Head

Your brain copes surprisingly well with missing pieces of the puzzle. It fills in the holes in our experience all the time, without us even noticing! Check out Professor Richard Wiseman revealing one such gap.

Missing Movementt

Your brain regularly suppresses information coming from your vision system and it's not just your blind spot. Look in a mirror and focus on your left eye. Now look at your right eye. Can you see your eyes moving? Watch a friend do the same thing and you should be able to see the difference. This phenomenon is known as saccadic masking.

Your brain constantly fills in the gaps so that your experience is consistent and uninterrupted. If faced with conflicting or ambiguous information it will make its best guess.

Puzzling Perspectives

Take a look at this picture of two horizontal rails. Which one is larger?

The converging lines of the railway track make us think the upper horizontal rail is further away and therefore must be larger but in fact the two horizontal rails are the same size. Try cutting a piece of paper to the same length to check.

One of our favourite demonstrations from the lecture was the Ames room. Watch Andy describe some of the challenges of building it.

From a certain viewpoint, it looks like a normal square room but actually it is distorted - one corner is bigger and further away than the other. We see the two corners as the same size and distance away, leading to a very odd effect when people stand in the room.

Here's another great perspective illusion that didn’t make it into the lecture.

You can watch all of Bruce Hood's CHRISTMAS LECTURES^® on BBC iPlayer and right here on the Ri channel.