The factor of need can sharply hone the perceptual process.
Mothers, for example, who lived near the elevated railway lines in New York could hear their baby’s tiny cry from another room against the very loud background roar of the trains passing by their window.
Piaget notes that a certain degree imbalance in the child’s (our) life is good in that it creates the need to adapt.
Needs, then, that are within the scope of the child’s ability to resolve will aid in the development of expectancies and hence, perceptual skills.
In other words, it isn’t necessary or even preferable to anticipate and meet every need for a child before it arises!
Short-Terms Sets: Most of the tricky examples that I have used above are short term sets.