In psychology, cognitive development is the study of neuroscience and the development of how a child processes information, social skills, language and other abilities.When studying cognitive development, there are three approaches to consider: biological, cognitive, and sociocultural. Psychologists study the development of a child’s brain and look closely at the biological, social, and cognitive factors in their environment since those can be influential. Important theories in cognitive psychology like Jean Piaget’s theory of child cognitive development, Lev Vygotsky’s sociocultural theory, and brain development with the support of Chugani (1999) will be evaluated.Jean Piaget was a swiss psychologist that focused his work in child development, and is most known for his theory of cognitive development. His theory stated that a child’s brain development happens in stages and they must complete one stage in order to go to the next. Children had to complete four stages: Sensorimotor stage occurs when the child is between 0 to 2 years-old which focuses on sensory and movement. The Pre-operational stage occurs between ages 2 to 7 years-old which involves symbolic thinking and restraints. The Concrete Operational stage occurs when the child is 7 to 11 years-old and children start solving problems logically. Lastly, the formal operational stage occurs at ages 11 to 16 years-old and children develop abstract thought. Piaget’s ideas influenced psychology and he changed the way psychologists perceived children while changing the methods of studying them, but his theory failed to acknowledge sociocultural factors on development. While he received praise for his work, his methods to conduct his theory received criticism. For example, Piaget had his children perform in an experiment known as the three mountain task. In this task, the children are shown a three-dimensional model of three mountains with a doll facing the mountains from a viewpoint different from the child’s. His research of the three mountain task was repeated many times and showed that children are able to see someone else’s point of view. Some argued that this test was too complex and unfamiliar to the children which resulted in bias. Also, Piaget would conduct interviews and observations on own children alone, which can result in massive researcher bias. He was only relying on his interpretations instead of having another researcher to compare data with. Similarly, the conservation tests have been argued to be too complex as well. This inspired further research which has been said that if the conservation task was more simplified, the children would be able to understand the concept much more easily. However, Piaget was correct in showing that children were capable for showing a bit of understanding logical structures. Piaget’s work is deemed valuable because he created the first comprehensive theory that changed developmental psychology and generated further research. Lev Vygotsky was a soviet psychologist who developed the sociocultural theory and later died because his ideas were too controversial for the Soviet ideology. Vygotsky’s theory stresses that the development of a child cannot be viewed separately from the child’s social culture. He emphasizes that the role of social interaction and language is important in a child’s cognitive development. An important part of his theory is the concept of “Zone Of Proximal Development” which is defined through three areas: what the child can do by themselves, what they can do with the help of an adult, and what they can’t do even with the help of an adult. His theory was said to be too “theoretical” with a lack of supporting studies, but Vygotsky died at the age of 37 which left much of his work unfinished and to be interpreted by other researchers. As for being too theoretical, his goal was to create a new paradigm in psychology which required much theoretical work. Most of Vygotsky’s research was based on a combination of experiments, interviews, observations, and clinical interviews because he was against artificial experimental conditions. As a result of this, all of his experiments are considered not to be strong experiments. Vygotsky’s work is demonstrated to add value to understanding cognitive development. When studying the development of the brain, researches used brain imaging technology to get an insight into the structure and processes of the brain. Chugani (1999) used PET scans to investigate glucose metabolism in newborn babies. This research demonstrated that glucose metabolism in newborn babies was most prominent in sensory and motor cortex. Brain imaging technology is practical and allows for individuals to be tested more than once. However, it can be limited because it cannot be used on everyone. PET scans require a patient to be injected with radioactive tracers which can be invasive and it is possible for a patient to be allergic to the tracer. PET scans are unable to do longitudinal studies and are very expensive. To conclude, brain imaging technology does have advantages and disadvantages, but contributes to investigating the brain in cognitive development. In conclusion, cognitive development is the study of how a child develops and processes new information, social skills, language and other abilities. Important theories and psychologists have helped contribute to further research in this field. Jean Piaget’s theory of child cognitive development has inspired and generated further research when it comes to children. His methods have been criticized, but those criticisms have helped advance his theory. Lev Vygotsky’s sociocultural theory created a new paradigm in psychology which required much theoretical work. As a consequence of that, all of his experiments were considered not to be strong experiments. Finally, brain development with the support of Chugani (1999) used brain imaging technology which contributes to further research in cognitive development and is shown to be useful in certain situations.