There are many theories in psychology that are related to different schools of psychology such as cognitive, humanistic, behavioristic, etc. These theories are propounded by eminent psychologists to provide a framework to understand different aspects of human behavior.'Lev Vygotsky', a Soviet psychologist, has propounded the "Socio-cultural Theory". This theory implies the idea that social interaction is the most important part of language learning and plays a crucial role in the learner's cognitive development. According to Vygotsky, social interaction is the primary cause of learners' development as his theory emphasizes that children learn through interaction and collaboration with skilled and knowledgeable people.Important PointsLev Vygotsky emphasizes the importance of social interaction in his theory by introducing three concepts which are as follows:More Knowledgeable Other(MKO)It refers to a person with a higher skill level and a better understanding of the concepts than the learners.ScaffoldingIt refers to a process through which temporary support is imparted to the learners to enhance learning to achieve goals.Zone of proximal development(ZPD)It refers to the difference between what a learner can do on his/her own and what he/she can do with help and guidance. HintMentalism refers to those branches of study that concentrate on perception and thought processes: for example, mental imagery, consciousness, and cognition, which are studied in cognitive psychology.In linguistics, mentalism is associated both with generative linguistics and the more modern approaches that go under the heading of cognitive linguistics. Mentalist linguists describe the mental patterns of language or the internalized grammar that underlie linguistic behavior.Hence, it could be concluded that mentalism term is not related to Vygotsky's socio-cultural theory.