Mind Games 2: Answers

7. Cranberry switch:

Pick up glass number two and pour the cranberry juice into glass number five.

Many people are familiar with matchstick tricks, where you move a match from one place to another – and we assume that this puzzle similarly involves changing the position of a glass. But pouring is another kind of moving – one that requires a little lateral thinking. Back to Mind Games.

8. Red hat, purple hat:

Kiki’s hat is red. How did she know?

a.) All the models knew that Guido had only three red and two purple hats.
b.) So when Anastasia said she didn’t know the colour of her own hat, the other models learned that Anastasia was NOT looking at two purple hats on their heads – if she were, then she’d know her hat must be red.
c.) That means at least one of the two remaining hats – Kiki’s and Babette’s – was red.
d.) When Babette didn’t know the colour of her own hat, Kiki realised that Babette was NOT looking at a purple hat: if she were, she would know her own hat was red, since at least one of the remaining hats had to be red.
e.) Therefore, Babette was looking at a red hat on Kiki’s head. Back to Mind Games.

9. Lilac chaser

This illusion is due to several different effects. When the eye fixates on something for a few seconds, it adapts to that particular colour. When the background changes, the eye sees the complementary (opposite) colour. So, when a lilac spot disappears, we see a green afterimage. (If the discs were blue, we would see yellow: every colour has its complementary.) In normal life, this is not a problem, because the eye unconsciously makes frequent tiny movements and does not fixate.

Afterimages quickly fade away – but in this case, a new one immediately appears, a little further along the circle. This creates a second illusion: we see these afterimage dots as a single moving object, just as the frames of an animated movie seem to show smooth movement.

Eventually, the lilac discs fade and we only see the moving green disc. This is because of a third effect: when you fix your sight on a particular point, unmoving things in your peripheral vision fade away, especially if they are small, blurred or low-contrast. Back to Mind Games.

10. Magic castle

As with the lilac chaser, this trick uses the brain’s tendency to create an afterimage in complementary colours. Back to Mind Games.