At which stage of cognitive development can a child reason the following All toffees are sweet. This candy is toffee. Therefore: This candy is sweet.?

Option 3 : concrete operational stage

Jean Piaget made a systematic study of cognitive development among children of different age groups and he categorized it into different developmental stages. He is also known as the father of child Psychology. According to him, development is based on the physical environment or Biological abilities, he ignores social aspects.

According to him stages of the cognitive development are-

• Sensory-motor:(birth to 2 years) 
• Preoperational: (from age 2 years to 7 years)
• Concrete operational:(from 7 years to 11 years) 
• Formal operational: (from11+ - adolescence and adulthood).

 Concrete Operational Stage:

• 'Concrete Operational Stage' lasts around 7 to 11 years of age which refers to the later childhood stage of child development.

• In this stage, children can classify objects into groups and subgroups and gain the ability to conserve numbers, area, and volume.
• Children show attainment of the concept of reversibility, seriation, and transitivity as a cognitive capacity.
• Logical mapping begins in a child so they analyze the problem, then think critically about it then comes to conclusion.
• Reversibility is the understanding that a child develops to know that things that have been changed can be returned to their original state.
• Children can conserve numbers (age 6), mass (age 7), and weight (age 9). Conservation is the understanding that something stays the same in quantity even when its appearance changes.

Thus logic mapping starts in the concrete operational stage, so the child can easily reason the logic in the given question. 

• Sensory-motor stage - This is a stage of the child from just after birth to two years. In this stage-
  • Senses are teachers.
  • Reflex action shows in children.
  • Intimate behavior by the child is shown.
• Pre-operational stage - This is a stage of the child from two years to 6 years. In this stage, there are many changes are shown in the child such as-
  • ​Language development starts.
  • Irreversibility in a child.
  • Egocentrism
  • Animism​
• Formal Operational Stage- According to Jean Piaget, this is a stage for a child who belongs from the age group of 11 years till adolescence. Changes are as-
  • Hypothetical- deductive logic begins.
  • Divergent/Convergent thinking.
  • Creative thinking.