What developmental milestone occurs when an infant can kick their feet to move a mobile?

The milestone of an infant kicking their feet to move a mobile is indicative of their developing understanding of cause and effect, which aligns with the concept of tertiary circular reactions. Tertiary circular reactions, a term coined by Jean Piaget in his theory of cognitive development, typically occur between 12 and 18 months of age. During this stage, infants begin to actively experiment with their environment. They learn that their actions can produce certain results, and they delight in exploring different ways to achieve the same effect.

For example, when an infant discovers that kicking their feet causes the mobile to move, they are engaging in a form of experimentation—possibly trying different kicks to see how the mobile reacts. This is a significant cognitive development step as it demonstrates purposeful action and the ability to manipulate the environment based on feedback they receive.

In contrast, secondary circular reactions, which occur between 4 to 8 months, involve infants repeating actions that produce a pleasurable outcome but lack the exploratory aspect of the tertiary stage. Reflexive stage refers to the earliest behaviors, where infants respond to stimuli reflexively rather than intentionally. Coordination of secondary reactions, seen between 8 to 12 months, involves the combination of previously established behaviors but does not yet include the active experimentation characteristic