Despite many detailed descriptive accounts of the developmental forms of memory, perception, and cognition in various phases of childhood (e.g. Piaget's work), often missing is an explanation for how or why the child develops these psychological processes (Karpov 2003: 138).
Because of its attention to causal dynamics, the neo-Vygotskian theory has been called "the most comprehensive approach to the problem of determinants and mechanisms of child development (Karpov 2003: 138)."
For example, children who lack opportunities to engage in rich, well-developed sociodramatic play during their preschool years appear to have greater difficulty with self-regulation and impulse control, characteristics associated with the diagnosis of attention deficit hyperactivity disorder (ADHD) (Bodrova & Leong 2007: 99) The proposed sequence of leading activities is not strictly determined by biological age, but rather by the typical age-related forms of adult and peer interaction in a given society (Chaiklin 2003: 48).
Karpov (2005) reviews recent empirical findings of Western researchers, which are highly consistent with the neo-Vygotskian analysis of child development through engagement in leading activities.
During the first year of life, emotional communication with caregivers is seen as the leading activity and context in which the developmental achievements of infancy occur.
While Piaget believed that infants' sensorimotor manipulation of objects came through spontaneous body movements and exploratory actions, evidence suggests otherwise.
Infants accept adults as mediators of their relations with the world, and show increasing interest in the actions they can perform with cultural tools and objects (Bodrova & Leong 2007).
Most often in recent Western psychology, the term "joint attention" has been used to describe these various triadic social skills and interactions (Moore & Dunham 1995).
Like Piaget (1963), Vygotsky believed that young children develop sensory-motor thinking, in which they solve problems with objects by using motoric actions and perceptions.
For instance, toddlers learn that different objects can serve the same function (e.g. that one can "drink" from a cup, mug, or bottle) (Bodrova & Leong 2007).
Perceiving culturally designated colors, shapes, and basic tastes are early examples of sensory standards that toddlers' learn through object interactions with adults (e.g. "Hand me the orange block").
As psychologist Karl Buhler put it, language is a tool or means for "one to inform the other about the things" (Bühler 1934, as cited in Müller & Carpendale 2000).
This language acquisition, in turn, is thought to restructure and develop children's other mental processes during the second and third years of life, including perception, attention, memory, and thinking.
In some historical or present traditional societies, however, role play may not be the leading activity during this age period, and children may engage more directly in apprenticeship and adult forms of work (Elkonin 2005a) Contrary to popular belief, adult mediation is critical in helping to children to achieve what Elkonin (2005b) called "mature" sociodramatic play.
It is important that children be exposed to various social roles, situations, and institutions in their schooling and life experiences, in order to have rich material for play.
They include: inhibition of impulses and self-regulation through adhering to playing a sociodramatic role; the overcoming of "cognitive egocentrism" by learning to take other points of view through playing various social roles; the development of imagination through voluntarily entering the imaginary situations involved in play; the ability to act on an internal mental plane; the integration of emotions and cognition; further development of object substitutions and symbolic thought; and development of the "learning motive" to continue to grow toward adulthood, which helps to propel children's next leading activity of learning in school (Karpov 2005).
To guide themselves, children often use speech or phrases that they have heard during collaborative action with peers or adults, and sometimes even imitate their caregiver's voice (Luria 1961).
For instance, rather than passively waiting for children to reach an appropriate developmental level before teaching certain concepts, as he interpreted Piaget's viewpoint, Vygotsky (1962) proposed that schooling should "march ahead of development and lead it."
Karpov (2005) emphasizes that children should also learn procedures for when and how to apply scientific knowledge to problem solving and everyday situations, and he gives some examples of this.
This includes the essential developmental ability to solve problems using abstract, theoretical information that goes beyond mere personal experience (Karpov 2003).
These theoretical reasoning capabilities are thought to be crucially important in children's transition to the next leading activity, interaction with peers (Bodrova & Leong 2007; Karpov 2005).
Authors point out that adults are still important mediators of adolescents' activity during this period, only less directly than when children were younger (Karpov 2005).
This further contributes to the development of formal-logical thinking in adolescents, making them capable of analysis of their feelings, goals and ambitions, morality, history, and their place in society, the existence of which they have just "discovered" (Karpov 2003: 150).
This motive has not been clearly defined in the literature, whether it has to do with cognitive advances, a desire to take on more adult roles, or sexual attraction to peers based in the reproductive developments of adolescence (Karpov 2005).