"The stroop test"

The Stroop Task is one of the classic cognitive psychological experiments named after John Ridley Stroop. He has done a series of experiments to find out “Stroop effect”, which demonstrates the delay in reaction time between compatible and incompatible stimuli conditions. For example, if there is a mismatch between the ink color and the word (e.g., GREEN), we will take longer time to name the correct ink of the word (e.g., Red). 
A game testing your own responses of Stroop effect

Reference:​

Stroop, John Ridley (1935). Studies of interference in serial verbal reactionsJournal of Experimental Psychology. 18 (6): 643–662. 

"How does child acknowledge the world"

A typical child on Piaget’s conservation tasks

Jean Piaget is a cognitive psychologist known for his work on child development. He created his conservation tasks to provide researchers with a way to evaluate the logic and reasoning abilities of children, and ultimately proposed a trajectory for cognitive development. Piaget explained that conservation is a cognitive understanding in which quantity remains the same even there are changes in appearance.

In this video, we can see how a 4.5-year-old child worked on Piaget’s conservation tasks and his cognitive understanding on number, length, liquid, mass, and area. In Piaget’s theory of cognitive development, the boy is at the “preoperational stage”. According to Piaget, children in this stage have not yet understood the concrete logic and cannot mentally “operate” information. 

Reference:​

Piaget, J. (1953). The origin of intelligence in the child. New Fetter Lane, New York: Routledge & Kegan Paul.