Critically evaluate the evidence supporting the nativist claim that infants of around three to four months of age have core knowledge of objects, including object permanence.
Over the past decade, a vast amount of research has examined young infants’ knowledge of objects. Nativists claim that infants have innate core knowledge about the world. Research by authors such as Baillargeon and Spelke proposed that very young infants are aware of object permanence, and the properties of objects, which allows them to ‘reason’ about events. The majority of research in this area was conducted using the habituation-novelty technique while measuring looking time. However, older research by authors such as Piaget claimed that object permanence does not develop until around eight to nine months of age. This finding was based largely on research involving errors made in object-search tasks. This assignment will critically evaluate the evidence supporting the nativist claim that infants of round three to four months have core knowledge of objects, including object permanence.
The nativist argument is insistent that infants are born with innate core knowledge about the world. Authors such as Baillargeon believed that this knowledge does not allow infants to represent the world exactly as adults do, but that this innate core knowledge is modified during development. Recent research has examined the habituation-novelty technique as a measure of object knowledge. This technique is a variation of methods used by Bower, whose research focused on object tracking and violation of expectation as a measure of object knowledge. Bower (1966) proposed that if young infants do in fact have knowledge of objects and object permanence then it would evoke surprise when objects disappear. This was demonstrated by Bower’s test for object permanence, in which young infants were presented with an object which was then occluded by a screen. After a short delay the screen was moved to either reveal the object or reveal nothing. Further research by Bower (1982) demonstrated that infants as young as 20 days old displayed surprise in the second condition, which was indicated by a change in heart rate. However this reaction occurred only when the object was occluded for a short period of time. This was described as a violation of expectation, that the infant would expect the object to reappear from behind the screen (lawful disappearance), when the object does not hence the violation of the expectation, that the object would appear (unlawful disappearance). Although this study would suggest that young infants demonstrate object permanence, many authors have failed to replicate these findings. Consequently, allowing us to question the validity of these results.
Baillargeon and colleagues used a number of methods similar to that of Bower, however these methods were based on a different rationale. Baillargeon used the habituation-novelty technique, in which an infant is repeatedly shown a lawful event, then shown two test events; either a lawful or an unlawful event. If infants have knowledge of objects then they should look less at the habituation stimulus as it is familiar, whereas they would look longer at the unlawful event as it would be unfamiliar and novel. Baillargeon, Spelke and Wasserman (1985) demonstrated this method with the “Drawbridge study”, in which five month old infants were habituated with a repeated event where a flap or “Drawbridge” rotated from a flat position 180° until flat against the table again, and then rotated back to the original position. Infants were then presented with two test trials in which a block was presented behind the flap as to obstruct the full rotation, in the possible event test the flap rotated to occlude the block and stopped on contact with the object. In the impossible event test, the flap made a full rotation and appeared to annihilate the block. The authors found that five month olds looked longer at the impossible event. Baillargeon later found these results with 3 and a half month olds and 4 and a half month olds. Baillargeon et al. (1985) therefore concluded that 5 month olds do have knowledge of object permanence and can understand that objects continue to exist when occluded by a flap. A criticism of this study is that the impossible event seemed to be more visually similar to the habituation event, this would therefore suggest that children would look longer at possible event as it was visually more novel. Rivera, Wakeley and Langer (1999) suggested that infants simply look longer due to preference of a longer rotation, however this is lost due to habituation. Rivera et al. (1999) found that by omitting habituation trials infants showed preferences to the 180° rotation, whether there was an object in the path of the drawbridge or not. This would therefore suggest that infants do not have knowledge of objects at this age and alternative explanations for longer looking times could be more valid.
Further research by Baillargeon (1986) found that infants of around six and eight month of age were able to detect an impossible event of a truck moving through a block, in which a truck ran down a track with a screen at the bottom of the ramp, the truck passed behind the screen and reappeared at the other side. Infants were familiarised to trials where the screen was lifted to reveal the track, then presented with two test events. The impossible event revealed a block placed behind the track, which was then covered by the screen suggesting that the block would not obstruct the truck. The impossible event revealed a block on the track suggesting an obstruction in the truck’s path. In both trials the truck emerged at the other side of the screen. Baillargeon and DeVos (1991) found similar results with four month olds. This would suggest that infants have knowledge of object permanence as knowledge is required to understand the block still exists even though it is out of sight, therefore infants are capable of understanding a truck cannot penetrate the block.
Baillargeon and DeVos (1991) showed three month old children can represent objects when they are covered behind a screen by representing the height of the object. The authors showed three-month-olds toy rabbits that were either short or tall. The objects disappeared behind a screen, in which a window was cut out at the top, and then reappeared. In the first condition infants were presented with a short toy rabbit, which was below the window level and therefore would not reappear until the object had passed fully from behind the screen. Infants were also presented with a tall toy rabbit in the second condition, which was tall enough to be seen through the window. In both test trials neither rabbit reappeared at the window, which was an impossible event in the tall rabbit condition. Infants looked longer at the impossible event, Baillergeon and DeVos (1991) concluded that infants can reason about the visibility of an object by representation of the height of the object. In addition the authors inferred that infants expected the rabbit to appear and their surprise that it did not shows that infants are aware of the existence of objects that are out of view. This demonstrated further the children understand object permanence. In contrast, research by Bogartz, Shinskey and Speaker (1997) challenge this notion, and argued that the methodology used by Baillargeon and DeVos (1991) was flawed. Bogartz et al. (1997) argued that with the short rabbit condition, infants were attracted to the facial features of the rabbit and therefore followed the screen at that height, not noticing the window within the screen. In the tall rabbit condition the infants scanned the screen at a greater height, noticing the window, therefore looking longer in the test trial due to the change in the screen. Detection of this change is determined by the infants’ attention during habituation. Bogartz et al (1997) conducted a replication of Baillergeon and DeVos’s study, but counterbalanced whether infants were habituated with lawful or unlawful events. The results showed that differences in looking time were explained by perceptual mismatches in habituation and test trial events, and not due to recognition of impossible events. The flaws in experimental methods allow us to question the validity of research findings, when alternative methodologies have offered a more plausible explanation.
Although it would seem superficially that these studies provide clear evidence that very young infants have knowledge of objects, research has not gone unchallenged. Haith (1998) argued that there are “Many factors affect looking, including variations in perceptual dimensions of objects and people, familiarity, novelty, recency, predictability and time lapse between stimulus exposures” (p.4), and therefore the limitation of using this method is that results rely on the interpretation of the researcher. In addition, Haith (1998) also argued that researchers must examine every possible interpretation of results to suggest that findings are only contributed to by one variable. It is overly deterministic to suggest that increased looking time provides evidence that infants have core knowledge of objects.
Older interpretations of object permanence in infants come from authors such as Piaget (1954), who took a more constructivist approach and proposed that infants are “little scientists”, in that, by interacting with the world children gain knowledge and can mentally represent reality. According to Piaget, infants do not demonstrate object permanence before the age of nine months, and object permanence does not fully develop until around two years of age. Piaget believed that infants were not born with knowledge of the world, instead this is gradually developed through the infants’ own experiences. This was explained by Piaget’s four stages of cognitive development, the first of which will be discussed. The sensorimotor stage, which occurs within the first two years of life, has six sub-stages. During the primary circular reaction stage (one to four months) Piaget suggested that children are egocentric and cannot differentiate between themselves and the world. This suggests that infants do not have core knowledge of objects at this age. In the secondary circular reaction stage (four to ten months), infants now begin to focus on objects rather than themselves. In the tertiary circular reaction stage (12 to 18 months) infants learn about objects through trial and error methods, and discover the properties of an object. In the final internal representation stage (18 to 24 months), Piaget proposed that infants are able to make representations of objects.
The key method Piaget used examined infants’ responses to object search tasks. Before nine months infants were unresponsive when an object was hidden, even if the infant was previously interested in the object which would motivate the infant to find the object. Piaget therefore claimed this showed if the object was out of sight it was therefore out of mind. Following nine months, infants reactions to hidden objects changed, in that the infants would successfully search and find the object, indicating the ability to mentally represent the object although absent. Furthermore, Piaget suggested that infants can only represent objects that are absent in one place, in the location in which it was found previously. Infants cannot represent objects which are moved to a new location, they search for the object in the old location, described as the A not B error. Therefore, if the nativist argument is correct, why is it that infants fail to search for hidden objects around 9 months of age, and continue to make search errors until around 18 months old? This may suggest that infants do not display object permanence at the early age of three to four months as claimed by the nativist psychologists. Although, a criticism of Piaget’s argument is that much of his research was carried out on his own three children, therefore this would suggest a bias or possibly lack of validity. However, a number of controlled experiments have been carried out which have found to replicate Piaget’s Findings.
An alternative explanation provided by Diamond (1990) suggested that the A not B error arose due to immaturity in the prefrontal dorsolateral cortex, associated with working memory. Diamond argued that infants can represent objects, and can make appropriate responses but cannot do these together due to the frontal cortex immaturity. Diamond suggested that infants display difficulty in retaining a short-term representation of an object and its’ location, and therefore make errors in object search tasks. Therefore until the brain has fully developed, infants do not demonstrate complete knowledge of objects, and not simply because the infant has not reached a certain stage of development. In addition, Bremner (1985) suggested that errors in object search tasks do not explain about infant’s knowledge of objects, but inform us of infants’ knowledge of location through successfully finding hidden objects. This contradictory evidence could be an alternative explanation as to why infants make search errors, due to having a different agenda to the experimenter.
To conclude, research carried out on infants to investigate their knowledge of objects and object permanence has not gone unchallenged. As demonstrated, there is a great deal of research supporting the nativist claim that children of three to four months old have core knowledge of objects, however the findings are all dependent on the researchers interpretation of the results. Previous research has not concluded that infants have innate capabilities of understanding objects, but have found contradictory evidence that it is learned through experience and development. However, this research has also been challenged. The nativist arguments can be described as too deterministic, not taking into account alternative explanations for infants increased looking time. Additionally, is it appropriate to suggest that looking time is an indicator of infants understanding of objects and object permanence? Or is a more sophisticated approach needed, possibly from a cognitive neuroscience approach? Either way, research on very young infants is still particularly tricky, and designing an ultimately fool proof experiment to measure infants knowledge of objects may be a task verging on the impossible. Further evidence is needed before we can accept the nativist claim that infants are inborn with knowledge of objects.
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