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Comparison of human infants and rhesus monkeys on Piaget's AB task: evidence for dependence on dorsolateral
1Section of Neuroanatomy, Yale University School of Medicine, New Haven, CT 06510-8001.
Insights
The dorsolateral prefrontal cortex is crucial for object permanence in infants. Ablating this area in monkeys mimics infant performance, suggesting its maturation supports cognitive development.
Area of Science:
- Cognitive Neuroscience
- Developmental Psychology
- Primate Neurobiology
Background:
- The development of object permanence in human infants (7.5-12 months) is linked to cognitive maturation.
- The AB task (A not B) assesses object permanence and is sensitive to cognitive development.
- Dorsolateral prefrontal cortex (DLPFC) is implicated in higher-order cognitive functions.
Purpose of the Study:
- To investigate the role of the dorsolateral prefrontal cortex in object permanence using the AB task.
- To compare AB task performance in human infants and non-human primates with specific brain lesions.
Main Methods:
- Administered Piaget's Stage IV Object Permanence Test (AB task) to human infants longitudinally.
- Administered the AB task to intact and operated adult rhesus monkeys with bilateral prefrontal and parietal lesions.
- Compared AB task performance with Delayed Response task performance in rhesus monkeys.
Main Results:
- Human infants showed improved AB performance with age, tolerating longer delays.
- Rhesus monkeys with bilateral DLPFC lesions exhibited AB errors at short delays (2-5s), similar to younger infants.
- Intact and parietally operated monkeys, along with older human infants, succeeded at longer delays (10s).
- AB task performance in monkeys correlated with Delayed Response task performance.
Conclusions:
- Dorsolateral prefrontal cortex (DLPFC) is essential for AB task performance in rhesus monkeys.
- Maturation of the DLPFC in human infants likely underlies the developmental improvement in object permanence between 7.5 and 12 months.
- This cognitive ability involves maintaining a goal in mind without external cues and guiding behavior flexibly.
Abstract:
This paper reports evidence linking dorsolateral prefrontal cortex with one of the cognitive abilities that emerge between 7.5-12 months in the human infant. The task used was Piaget's Stage IV Object Permanence Test, known as AB (pronounced "A not B"). The AB task was administered (a) to human infants who were followed longitudinally and (b) to intact and operated adult rhesus monkeys with bilateral prefrontal and parietal lesions. Human infants displayed a clear developmental progression in AB performance, i.e., the length of delay required to elicit the AB error pattern increased from 2-5 s at 7.5-9 months to over 10 s at 12 months of age. Monkeys with bilateral ablations of dorsolateral prefrontal cortex performed on the AB task as did human infants of 7.5-9 months; i.e., they showed the AB error pattern at delays of 2-5 s and chance performance at 10 s. Unoperated and parietally operated monkeys succeeded at delays of 2, 5, and 10 s; as did 12 month old human infants. AB bears a striking resemblance to Delayed Response, the classic test for dorsolateral prefrontal function in the rhesus monkey, and indeed performance on AB and Delayed Response in the same animals in the present study was fully comparable. These findings provide direct evidence that AB performance depends upon dorsolateral prefrontal cortex in rhesus monkeys and indicates that maturation of dorsolateral prefrontal cortex may underlie the developmental improvement in AB performance of human infants from 7.5-12 months of age. This improvement marks the development of the ability to hold a goal in mind in the absence of external cues, and to use that remembered goal to guide behavior despite the pull of previous reinforcement to act otherwise. This confers flexibility and freedom to choose and control what one does.