Ans. a. Sensory-motor stage (Ref: Niraj Ahuja 6th/156)In Piaget's theory of cognitive development 'out of sight, out of mind' and 'here and now' is seen in Sensory-motor stage.Jean Piaget Theory of Intellectual DevelopmentIntellectual development goes hand-in-hand with the development of physical and behavioral characteristics.According to Jean Piaget, it can be divided into the following stages:Sensori-Motor stage:Extends from birth to 2 years of ageCharacterized by:Actions related to suckling, orality and assimilation of objectsAbility to think of only one thought at a timeInanimate objects are given human qualities'Out of sight' means ceasing to existConcrete Thinking stage:Lasts from 2 years to 7 yearsCharacterized by:Egocentric thought with a unique logic of its own, involving a limited period of view and lacking introspectionInability to generalize from specific events and to specify from general eventsAbstract or Conceptual Thinking stage:Begins at 7 years of age and lasts till 11 years of age, although it may be said to continue throughout life.Characterized by:Ability to focus on several dimensions of a problem at one time, mentally.The thought process is flexible and reversibleAbility of abstraction, i.e. ability to generalize from specific and ability to find similarities and differences among specific objects.Adolescent thinking or Formal Operational Stage:Begins at 11 years of age and continues lifelong.Characterized by:Ability to imagine the possibilities inherent in a situation, thus making the thought comprehensiveAbility to develop complete abstract hypotheses and to test themBy the end of adolescence, the individual's intellectual ability is nearly completely developed, although learning and intellectual growth go-on throughout the life span of individual.