Lev Vygotsky', a Soviet psychologist, has propounded the "Socio-cultural Theory". This theory implies the idea that social interaction plays a crucial role in the development of learners' cognitive ability. Vygotsky has proposed the concept of 'Zone of Proximal Development (ZPD)' in his "Socio-cultural Theory". ZPD refers to the:difference between what a learner can do on his/her own and what he/she can do with someone's help.distance between the learner's actual development level and his/her level of development under someone's guidance.range of task too difficult for the child to do alone, but possible with the help of adults and more skilled peersHence it could be concluded that the term Zone of Proximal Development (ZPD) is related to socio-cultural theory.HintBehaviorist Approach is largely responsible for establishing psychology as a scientific discipline through its objective methods and especially experimentation.Psycho analytic theory highlights the role of unconscious thoughts, feelings, memories, and early childhood experiences in determining behavior.Cognitive development theory suggests that a child first becomes aware of a concept, such as relative size, and only afterward do they acquire the words and patterns to convey that concept.Additional Information Other Important Terms Proposed by Vygotsky in his 'Socio-cultural Theory':Scaffolding: It refers to a process through which temporary support is imparted to the learners to enhance learning to achieve goals.More Knowledgeable Other(MKO): It refers to a person with a higher skill level and a better understanding of the concepts than the learners.