The effects of neglect on the developing brain

     To learn about the effects of a bad environment on a developing human brain, researchers obviously can’t conduct the same kinds of experiments they might perform on rats or monkeys. Instead, they have to rely on data gathered from “natural” experiments.

     Recently, hundreds of Romanian orphans were adopted into good homes after having suffered unconscionable neglect in orphanages under the Ceausescu regime. The conditions in those orphanages resembled the kind of “impoverished” environment that researchers impose on rats in biological experiments. The orphans were confined to cots, with few playthings and little attention from caregivers.

     When they arrived in their adoptive countries, the orphans were severely impaired in their development. By following their progress, researchers have been able to gather data about what age, if any, is too late to fix brain development problems caused by early deprivation.

The researchers have mostly good news to report. For most of the children, cognitive catch-up was essentially complete within a few years. At the same time and here is where the encouraging  findings need to be qualified the older adoptees haven’t caught up completely.

The encouraging conclusion is that the human brain is very resilient. Even severe deprivation during the first few years of life can be overcome to a remarkable degree. For the Romanian orphans, there was no point at any time during the first three and a half years of life when any development window slammed shut. 

The influence of inherited genes

     Most types of Specific Language Impairment (SLI) are caused by the failure of many genes to interact as intended. However, a recent study has identified a single gene responsible for a language disorder found in about half of the members of one family living in London. Though they are all normal in other ways, their speech disorder is so obvious that people outside the family can’t understand them. It appears to result from the disruption of a single gene on chromosome 7, in the same area as a gene that has been linked to autism.

     Many researchers believe that some class of SLI may not be specific to language at all. In their view, the disorder may sometimes result from a problem with working memory, a short-term memory system for storing information, manipulating it, and using it to solve a problem. Some SLI sufferers may have difficulty with their short-term memory for speech sounds. In other cases, the short-term memory problem may be more general. One experiment showed that some SLI children have difficulty remembering and repeating back any sequence of sounds that they hear, even if they are not speech sounds. A well-functioning working memory helps with performance on a variety of language and reading related skills, such as building a good vocabulary, learning a foreign language, and becoming a proficient reader.

Specific language Impairment

     There are, however, exceptions. Mental retardation or deafness can block a natural path to acquiring a language. Chemical influences or physical accidents suffered by a fetus, or genes that are activated in abnormal ways, can make normal language learning difficult for otherwise healthy, intelligent children. A number of these diversities have been lumped by psychologists under the general name of Specific Language Impairment, or SLI

     These SLI disorders relate only to language ability. They are not part of some general problem of cognitive development, intelligence, emotional trauma, or impoverished environment. The fact that some children are apparently born with brains that function well in all skills but language may mean that there are specific genes that code for language-processing regions of the brain and that may go awry. All the language disorders are more common among boys and girls, and all have a tendency to run in families. SLI are mainly caused by the failure of genes.

Language learning

     Children all over the world have a natural urge to learn language built into their genes. Virtually any infant is genetically equipped to develop the motivation and brain circuits needed to learn the one or more languages it hears spoken around it, without any special help or instruction. Parents need never give lessons in how to change a verb into the past tense, or explain the significance of the difference in sound between for and far. A normal child learns such things just by listening.

     By the age of four, a child will have become fluent through a sequence of stages that are pretty much the same for any child, and for any language, the world over. One-word utterances at age one lead to multi-world phrases a year later. A one-and-a-half-year-old’s vocabulary of 50 words expands to 10,000 within five years. A tow-year-old’s baby talk matures by age seven into mastery of the full repertoire of all the sounds in the language. On average, as the language-learning systems within the brain unfold, girls have a tendency to be a little more precocious than boys. 

Processing visual information

     Strategies for processing visual information also change as a child’s brain develops. Tests of toddlers  vs.  preschool children show that the younger ones recognize people by picking out specific visual clues such as  a moustache, hairline, glasses or skin color. That’s why at Halloween, for example, a toddler might burst into screams when daddy puts on a funny nose. In the child’s eyes that difference is enough to turn a familiar loving face into a complete stranger. Older children’s brains have developed sufficiently to use the adult strategy for recognizing faces as being familiar or strange. They are able to scan quickly for an overall abstract pattern of lights, darks, hues and forms.

     But, of course, there’s only a correlation to some degree between information-processing speed in infancy and IQ later in life. Why only to some degree? Assuming processing speed is stable, there must be other factors that bear on a person’s developing intelligence. What factors?  You can see how an interest in novelty would do little good if the environment  didn’t  provide enough new things to explore, while a richer environment might help an infant learn more skills even if the brain processes information a little more slowly. All children have a natural urge to learn and explore. The only thing that can really get in the way of that inborn predilection is a lack of things to explore. In this sense, environment always has the final say in the development of intelligence. 

“Short looker” or a “Long looker”

     Psychologists have also found that some babies are “short lookers” and others are “long lookers.” That  is, some fix their attention for a longer period of time on a new object the first time they see it. You might think long lookers are taking in more. In fact, though, short lookers may have an advantage. Long lookers need more time to investigate the same amount of information as short lookers, and sometimes even take in less information overall than short lookers. Short lookers may be more adept, in other words, at taking in and processing new information.

     Many neuropsychologists think this kind of speed of information processing might translate into better performance on an IQ test a few years down the road, assuming that information processing speed is something built into our brains from birth and, therefore, fairly stable throughout life. Some researchers even propose that a positive response to novelty defines intelligence. There does seem to be evidence that some brains operate relatively more quickly, in this way, than others. Researchers have found that infants who are quicker in the novelty tests also, on average, perform better on IQ tests in early and middle childhood. So some people may have an advantage over other from infancy.

An early sign of intelligence

     Many parents are proud of their children if they learn how to do something – walk, talk , tie shoelaces – at a younger age than the neighbor’s child. Is it true that more precocious development leads to greater ability or intelligence later in life? Are there other kinds of infant behavior that have this kind of predictive value? Can you tell how smart the ten-year-old is going to be by looking at the ten-month-old? And is there anything you can do about it?

     Observers of child development, including mothers with more than one child, know that infants and children have their own timetable for learning and acquiring skills. Intelligence unfolds over years, sometimes in spurts that some researchers think correspond to rapid development of synapses between brain cells. The order of stages can’t be changed, and most researchers believe that the developmental stages can’t be accelerated. Different kinds of learning require different developmental stages to have been reached, and there’s nothing parents can do about it. A child can’t learn mathematical set theory, for example, before the ability to understand symbols and the concept of categorization have been installed in the developing brain.

All tongues, but what an infant hears, becomes foreign

     Most of us have heard the claim that infants can produce the sounds of any language before they learn which small subset of that universal inventory their own language requires. Actually, this claim isn’t quite true. All infants find some speech sounds easier to produce than others. Vowels are easy, as are consonant sounds such as “b,” “n,” or “d.”  Fricatives (“f,” “th,”  etc), affricates (“ch”), and                liquids (“r,” “l,”) are universally harder to produce and are, therefore, relatively rare at this early stage.

     On the other hand, a very young infant does have a remarkable ability to hear all the sounds, and differences in sounds, exploited by any of the world’s  3,000 languages – despite the fact that most of those distinctions are ones their own mother tongue doesn’t use. For example, a four-month-old Japanese infant can easily differentiate an “l” from an “r” sound, even if the parents can’t.  And an American four-month-old  born into an English-language environment can discern differences between Chinese-language tones that are beyond the abilities of its parents.

     What quickly begins to happen, though, is that the infant’s ears become less acute. Of course, it’s not literally the ears that are changing, but the brain, which is adjusting its phonetic-perception circuitry to the needs of just one language.