As one-year olds play, they start to recognize patterns and
understand shapes. They begin to sort familiar objects by one
characteristic, such as whether they are "hard" or "soft." They
may enjoy filling and emptying containers. They notice that
night is followed by day, and that socks go on feet before
shoes. They know that when an object is hidden, it is still
there. Many can also do simple insert puzzles when the puzzle
pieces show whole objects. Between 18-24 months, some children
will begin to use a few number words without understanding
quantity (e.g., imitates a simple counting rhyme). Some children
may also begin to understand the words "one" and "two" (e.g.,
distinguishes "one" or "two" from many; identifies pairs of
items as "two;" identifies three or more items as "many" rather
than as "one" or "two;" asks for "one" or "two" of something;
knows age; responds appropriately to the request, "Take just
one," or "Give me two."). Between 18-24 months, a few children
will begin to nonverbally and mentally