Final answer:
In Piaget's sensorimotor stage, secondary circular reactions refer to repeated actions by infants to cause effects in their environment, which aids in understanding causality.
Step-by-step explanation:
In the sensorimotor stage of cognitive development, a substage known as secondary circular reactions occurs. During this phase, which typically spans from about 4 to 8 months of age, infants start to repeat actions that produce effects in the environment, independent of their own bodies. For example, a baby might accidentally hit a mobile and delight in the movement and sounds it creates. The baby then intentionally hits the mobile again to repeat the enjoyable experience. This illustrates how children at this stage learn about cause and effect relations in their surroundings by engaging in behaviors that have observable outcomes.