The concept that objects continue to exist even though they cannot be seen or heard is termed as: 

In cognitive development, children gradually understand that objects and people exist independently of their perception. 

Key Points

• The concept that objects continue to exist even when they cannot be seen or heard is called "Object Permanence." This term was introduced by Jean Piaget in his theory of cognitive development, specifically during the sensorimotor stage (birth to 2 years).
• Infants initially believe that objects disappear when they are out of sight, but as they develop, they begin to understand that objects have a continuous existence even if they are hidden.
• This realization marks a significant cognitive milestone and supports later skills such as memory, problem-solving, and symbolic thinking.

Thus, it is concluded that the concept that objects continue to exist even though they cannot be seen or heard is termed as Object permanence.

Hint

• Accommodation refers to the process of modifying existing cognitive structures when faced with new information.
• Assimilation is the process of incorporating new experiences into existing cognitive schemas without changing them.
• Mental equilibrium refers to the balance between assimilation and accommodation, allowing cognitive stability and learning progression.