The understanding that objects continue to exist even when they cannot be seen or heard. For example, a toddler with object permanence would know that a hidden toy still exists, even if it is out of sight.
The tendency for young children to only see things from their own perspective and struggle to understand other people's viewpoints. This can contribute to the difficulty in searching for hidden toys since toddlers may assume others know what they know.
According to Piaget's theory, the first stage of cognitive development (from birth to around 2 years old), during which infants and toddlers learn about the world through sensory experiences and actions on objects. This stage is characterized by rapid cognitive growth and the emergence of basic mental representations.