Spot the Different One fills the board with matching pictures and hides one impostor among them. A cat among tigers. A tomato among apples. Find it.
What your child is learning
This is a game of visual discrimination: noticing small differences between things that look alike. It is the same skill that later separates "b" from "d", "was" from "saw", and 6 from 9.
It also trains a child to search in an organised way, to keep going until the whole board has been checked, and to concentrate for a little longer each time.
The pairs have been chosen to be similar but not identical: two round fruits, two yellow fruits, two kinds of ball, two faces. The first questions show four pictures. After that there are six, and the last few show nine.
How to help
Let your child look first. Often the odd one simply jumps out, and that quick recognition is worth praising.
When it does not, look in order. Point along the top row, then the next, as you would read a page. This left-to-right, top-to-bottom sweep is good preparation for reading.
Ask how it is different. "What is not the same about this one?" Putting it into words, "it has stripes", or "it is a different yellow", deepens the looking.
Name both pictures: "These are all frogs, and this one is a turtle."
If your child taps at random, cover part of the grid with your hand and check a few at a time.
Taking it further
Line up toys with one odd one out. Lay out spoons with one fork among them.
Spot-the-difference pictures in comics and activity books build the same skill.
No reading is needed. For careful-looking practice, HTML5 games like this one are quick, cheerful and easy to repeat.