USING THE TOILET
It seems the right time for using the toilet often becomes clear in the child's behaviour. The child becomes aware of his bowel movements and peeing, becomes more and more interested in what is in his diaper, in the toilet, and he will eventually show interest himself in using the toilet or potty.
Many children will be interested at first, and even use the toilet regularly for a time, and then regress to a diaper for a while. It may simply be that their interest and learning focus is elsewhere, and that the toilet business is too much to be aware of as well. Being positive, noting habits and rhythm, being attentive to their body language and where their attention lies can help support the transition to using the toilet without pushing them into it before they are ready.
 Davis, Laura and Janis Keyser. Becoming the Parent You Want to Be. Broadway Books, New York 1997
The bath by Mary Cassat
FROM ONE TO THREE