Perhaps young infants, brand new in the world, experience their environment as a kind of nonsensical dream in which even the simplest properties of objects surprise them. Wow, they wonder, where does the world go to when I close my eyes?Or perhaps they do have some intuitive understanding that objects continue to exist even when they can't be directly experienced? This is the question psychologists have been trying to answer while researching what infants in their first year of life understand about 'object permanence'.
Object permanenceObject permanence is the understanding that objects continue to exist even when we can't actually see them. Famous Swiss psychologist Jean Piaget thought that children couldn't properly grasp this concept until they were at least 12 months of age.This idea was challenged by a series of studies carried out by Professor Renee Baillargeon from the University of Illinois and colleagues. These studies used children's apparent surprise at 'impossible' events to try and work out whether they understood object permanence.
A blocked roadIn one study infants as young as 6.5 months watched a toy car travelling down a ramp. Half way through its journey, though, it went behind a screen out of the baby's view before exiting the other side, once more visible. In one condition the infants saw a block placed behind the screen in the way of the toy car. And yet when the car was released, experimental trickery was used so that the block didn't stop the car's progress. Miraculously it still appeared from the other side of the screen.This 'impossible' condition was compared with another condition where the block was placed near, but not in the way of, the car's progress - the 'possible' condition.Baillargeon found that the infants looked reliably longer at the seemingly impossible scenario. This suggested they understood that the block continued to exist despite the fact they couldn't actually see it. They also must have understood that the car could not pass through the block. This seems like reasonable evidence that infants can understand object permanence.
Simple explanationIn further studies Professor Baillargeon tested all sorts of variations on this theme. Toy rabbits, toy mice and carrots were all used, with some defying the laws of nature in the 'impossible' conditions and others studiously following them in the 'possible' conditions. Each time, though, infants looked longer at the apparently impossible events, perhaps wondering if they were dreaming. These studies have now shown that infants as young as 3.5 months seem to have a basic grasp of object permanence. While others have argued for alternative explanations and interpretations, when all these studies are taken together the idea that children understand object permanence is arguably the simplest explanation.
Intuitive physicistsUsing these results Baillargeon and others have argued that young infants are not necessarily trapped in a world of shapes which have little meaning for them. Instead they seem to be intuitive physicists who can carry out rudimentary reasoning about physical concepts like gravity, inertia and object permanence.
Sunday, July 13, 2008
Infants first Word
An infant's very first step in their year-long journey to their first word is perhaps their most impressive. This first step is discriminating and categorising the basic sound components of the language they are hearing.
To get an idea how hard this might be think about listening to someone speaking a language you don't understand. Foreign languages can sound like continuous streams of noise in which it's very hard to pick up where one word starts and another word begins.
Young infants face an analogous challenge but not initially at the level of words, but at the lower level of pure noise. Their first struggle is to tell the difference between the most basic components of speech, the individual sounds we are making, the phonemes.
Noticing the difference between 'b' and 'p'Until a classic study carried out by Peter D Eimas and colleagues from Brown University in 1971, psychologists were not sure how soon infants could discriminate phonemes.
Eimas and colleagues' study used infants aged between just 1 and 4 months old and tested their ability to discriminate between a 'b' sound and a 'p' sound (Eimas et al., 1971). To get an idea of how difficult this is, consider the fact there's only a 10ms difference in timing between the two. To be able to hear this difference, a baby has got to have a very fine-tuned ear.
The method they used for intuiting whether the infants had noticed a change from one sound to the other was pretty ingenious. They were hooked up to a fake nipple which measured their rate of sucking, the idea being that this was a proxy for how interested they were in what was going on around them. The more interested, the faster they suckled.
First, infants' suckling rates were measured while they were exposed to one repeated sound, say the 'b'. Initially infants found this interesting and sucked a bit faster. Then after a while they get bored and there suckling rate reduced.
Here's the crucial part: in some experimental conditions the sound is changed to a 'p', while in other conditions it continues with the same 'b'. The question is whether infants notice this change, as evidenced by an increased suckling rate, and thereby demonstrate that they can discriminate the tiny difference between a 'b' and a 'p' sound.
Innate ability to discriminate phonemesWhat Eimas and colleagues found was that even the one-month old infants appeared to be able to tell the difference between a 'b' sound and a 'p' sound.
This findings, and more like it, suggests to many psychologists that infants are born with skills which enable them to categorise sounds that only slightly vary. This skill is one of the basic building blocks of language learning.
Most languages contain about 40 distinct phonemes and an infant's ultimate task is to master all of them. During their first three months of life infants make all kinds of sound, but none of them bear much resemblance to speech.
But, partly because of this innate ability to discriminate the components of speech, by 3 months they start producing vowel-like sounds. They've conquered their first few phonemes and are well on their way to their first words.
The first wordWhile infants seem to be born with an ear fine-tuned for language, this starts to subtly change at around 11 months of age. Subsequent findings have shown that adults cannot successfully distinguish as wider a range of phonemes as infants.
This is because until about 11 months of age infants are masters of discriminating phonemes used in all different types of languages. But after 11 months infants settle down with one set of phonemes for their first language, and lose the ability to discriminate the phonemes from other languages. Infants are beginning to specialise in their own language.
The specialisation at 11 months in one set of around 40 phonemes, along with other linguistic processes, is clearly crucial as it quickly brings a magical moment: the first word.
To get an idea how hard this might be think about listening to someone speaking a language you don't understand. Foreign languages can sound like continuous streams of noise in which it's very hard to pick up where one word starts and another word begins.
Young infants face an analogous challenge but not initially at the level of words, but at the lower level of pure noise. Their first struggle is to tell the difference between the most basic components of speech, the individual sounds we are making, the phonemes.
Noticing the difference between 'b' and 'p'Until a classic study carried out by Peter D Eimas and colleagues from Brown University in 1971, psychologists were not sure how soon infants could discriminate phonemes.
Eimas and colleagues' study used infants aged between just 1 and 4 months old and tested their ability to discriminate between a 'b' sound and a 'p' sound (Eimas et al., 1971). To get an idea of how difficult this is, consider the fact there's only a 10ms difference in timing between the two. To be able to hear this difference, a baby has got to have a very fine-tuned ear.
The method they used for intuiting whether the infants had noticed a change from one sound to the other was pretty ingenious. They were hooked up to a fake nipple which measured their rate of sucking, the idea being that this was a proxy for how interested they were in what was going on around them. The more interested, the faster they suckled.
First, infants' suckling rates were measured while they were exposed to one repeated sound, say the 'b'. Initially infants found this interesting and sucked a bit faster. Then after a while they get bored and there suckling rate reduced.
Here's the crucial part: in some experimental conditions the sound is changed to a 'p', while in other conditions it continues with the same 'b'. The question is whether infants notice this change, as evidenced by an increased suckling rate, and thereby demonstrate that they can discriminate the tiny difference between a 'b' and a 'p' sound.
Innate ability to discriminate phonemesWhat Eimas and colleagues found was that even the one-month old infants appeared to be able to tell the difference between a 'b' sound and a 'p' sound.
This findings, and more like it, suggests to many psychologists that infants are born with skills which enable them to categorise sounds that only slightly vary. This skill is one of the basic building blocks of language learning.
Most languages contain about 40 distinct phonemes and an infant's ultimate task is to master all of them. During their first three months of life infants make all kinds of sound, but none of them bear much resemblance to speech.
But, partly because of this innate ability to discriminate the components of speech, by 3 months they start producing vowel-like sounds. They've conquered their first few phonemes and are well on their way to their first words.
The first wordWhile infants seem to be born with an ear fine-tuned for language, this starts to subtly change at around 11 months of age. Subsequent findings have shown that adults cannot successfully distinguish as wider a range of phonemes as infants.
This is because until about 11 months of age infants are masters of discriminating phonemes used in all different types of languages. But after 11 months infants settle down with one set of phonemes for their first language, and lose the ability to discriminate the phonemes from other languages. Infants are beginning to specialise in their own language.
The specialisation at 11 months in one set of around 40 phonemes, along with other linguistic processes, is clearly crucial as it quickly brings a magical moment: the first word.
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