Habituation technique,:
relies on the fact that children, like adults, lose interest if they look at the same object or event over and over again.　

violation of expectations’ technique:-

similar to the habituation technique but relies on the principle that people spend longer looking at events that they believe to be impossible.

One of the variants involves a possible event that is different from the original event, and the other variant is an impossible event, which is the same as the original event but made ‘impossible’ by some new feature -

Baillargeon (1986) experiment the rolling car