First of all both of the Vygotsky's and Piaget's theories interested in particular aspect of the cognitive development. However, Piaget's theory emphasizes the importance of stages (sensorimotor(0-2 years), pre-operational(2-7 years), concrete operational(7-11 years) and formal operations) for cognitive development, and learning as a function of age; according to Vygotskian perspective, development process from birth to death is too complex to to be defined by stages( Driscoll, 2005). Also, both of the theories belived that learning occurs from birth to death so it is a continous process. For both of the two theories, knowledge is internal for learner. For Vygotksy, learning occurs begins as social activities by interacting with other people and people internalize these processes and can use them independently. For Piaget, individual acquire knowledge from their interaction with the world and then take those concepts and makes sense the world through cognitive schemes and these schemes are changed as a result of individual actions on objects in the world. So, children might even learn playing his toys.
Piaget and Vygotsky also differ in terms of the view of learning and development. While Piaget's theory suggests that after cognitive development, learning occur, Vygotsky's theory claims that learning can lead development and sometimes after development learning occurs.
Another similarity between the theories of Piaget and Vygotsky is the acquisition of speech. Both of them considered that acquisition of speech is the major activity in cognitive development. However, they differ from each other in terms of the view of egocentric speech. For Piaget, egocentric speech is the characteristic of preoperational stage and this speech disappears when child moves from preoperational to concrete operational stage (Gredler, 2005). Egocentric speech reflects the egocentric thoughts, feelings and reasoning patterns for a preoperational child. In contrast, according to Vygotksy's point of view, egocentric (private) speech does not disappear but becomes inner speech. Moreover, egocentric speech is an important transitional stage between social speech and inner speech. Inner speech reflects the verbal thoughts for Vygotskian perspective and people think verbally to guide their thinking and actions during their life.
Piaget's instructional approach is based on constructivism. According to Piaget's theory knowledge is an individual constructs. The major principle of instruction is to use methods that include prior knowledge and the techniques that cause assimilation and accommodation. For Piaget, supporting the spontaneous research of the child gives opportunities for interacting with physical world and can lead discovery learning (Gredler, 2005). On the other hand, Vygotsky suggests the guided discovery in the classroom that students are still receving assistance from more knowledgeable partner during discovery process. For Piagetian Perspective, causing cognitive conflict by surprising students can gain students' attention and lead to make sense the world through cognitive schemes. Also, while Piaget's theory emphasizes that the instruction should be designed taking students' developmental stage into account because students do not yet have the mental capacity to solve such a problem Vygotsky's theory offers encouragement and providing assistance in the form of scaffolding, in order to the student to attempt and solve the problem. According to Vygotsky, with the help of more knowledgeable partner the child can complete a task when he cannot do unassisted. This refers the zone of proximal development, the gap between what child can do individually and what child can do with assistance, is one of the most important terms of Vykotsky's theory. In both of the theories instruction should be designed taking students 'active involvement into account.
For Vygotsky learning is a social process and begins as social activities by interacting with other people and people internalize these processes and can use them independently. So, applications of the theory in instructions should involve social interaction and a guided teacher or expert. Also, Piaget gives importance peer instruction for learning. Instructional scaffolding, reciprocal teaching, peer collaboration and apprenticeship are some applications of Vygotsky's theory which involves social interaction (Schunk, 2008). Moreover, providing opportunities for class discussion, allowing group work can help improve learning in a social environment.
Role of teacher
For both Vygotksy and Piaget, teacher has role as facilitator and guide. But guidiance of teacher is much more in Vygotsky than Piaget. According to Vygotskian perspective teacher is one of the required factors for teaching as they are more capable than students. For Vygotsky, teacher direct students while scaffolding process and try to provide assistance about how the learner can achieve his goal even without the assistance. A Vygotskian teacher's aim is creating self-regulated learners. In Vygotsky's theory, role of teachers is to provide the guidance required for learners to bridge the distance between their current skill level and a wanted skill level. But for Piaget, teacher is an organizer who guides stimulating plan and research. Teacher encourages stimulate and support exploration and invention and recognize and what provides disequilibrium and curiosity for children and how to use it in an appropriate way.
Like Vygotksy, Piaget also believes that cognitive skills develop through active interaction. Piaget emphasizes the importance of interaction which leads disequilibrium among peers. He views social interactions as source of cognitive conflict, equilibrium, and development. However, the basis of Vygotksy's theory is social interaction and culture. Vygotksky seems social interaction as only way of learning. According to Vygotksy, people learn with social interaction from environment then construct knowledge individually.
Vygotksy's theory empasizes that every higher mental function was interpersonal or social before, then it became an interapersonal mental function. However; for Piaget social interaction is one of the tools that help to occur disequilibrium.
For For both Vygotksy and Piaget's give importance prior knowledge form different aspects. In Piaget's theory children acquire new knowledge with accommodation and assimilation of existing knowledge. So, prior knowledge is an important term in learning for Piagetian perspective. Prior knowledge also important for Vygotskain view in terms of scaffolding. Because, teacher need to give less assistance if there is more prior knowledgeable person.
Role of the learner
For Piaget and Vygotksy learner are active in learning processes. According to Piaget, learner acquires his own form of existing knowledge through their personal construction of knowledge. For Vygotsky, children learn in a social interaction in a social environment, while for Piaget learning is made by the learner individually. Vygotsky claims that in learning process learner requires assistance of teacher or more capable peers. The guide of the others is not seen as much as in Piaget's theory as in Vygotsky's theory.