So 4 is an even number. An odd number cannot be shared equally into two groups. For example, these 3 cubes cannot be shared into two equal groups. You have a group of 2 cubes and a group with 1 cube.

A second group got the reverse: Odd-numbered cards had a reward, while even-numbered cards delivered bitterness. The bees learned—quickly. Even as researchers raised the number of shapes per ...