Twins
The same factors that give rise to uncanny physical similarities between twins--similarities are mirrored in genetic similarities that can have more negative impact. Australian researcher David Hay has found that one type of identical twin seems to be plagued with developmental difficulties, especially in language acquisition, and that both parents and teachers add to these difficulties by responding more positively to the older of the two.
Hay has found that just as many identical twins are "mirror images" of one another--with the facial structure, dominant hand and even fingerprints of one exactly reversed in the other---their brains also seem to reflect the same phenomenon.
Questions about Identical Twins
"It is almost impossible to find identical pairs (of twins with the same brain structure)," says Hay, who presented some of his findings on twins at the International Society for Twin Study Conference in Amsterdam in September. "There is generally no relationship between how their brains function; the twins work and think differently." "The left half of the brain controls language skills in one twin while in the other it is the right half," he continues. "So one twin may have difficulty in the reception of language and the other in communication."
"We still have piles of questions about identical twins," he adds.
Hay heads one of the world's largest studies on twins at LaTrobe University in Melbourne, and has studied 587 sets of twins and their siblings over the last 10 years. He has found that both genetic and social factors combine to put twins at a disadvantage, but that steps can be taken to set the youngsters on the path to normal development. The twins who experience the bulk of the problems are the second of two types of identical twins, says Hay. The first type, comprising one-third of all identical twins, results when the fertilized egg splits three to four days after conception. These embryos have separate placentas. The second group forms when the egg divides four to eight days after conception. They share the same placenta, and are "mirror image" twins in about 70 percent of the cases. This group is at the highest risk for a range of social and learning problems, as well as for congenital abnormalities such as spinal bifida and cleft palate. Hay points out that twins traditionally have been known to have difficulties acquiring language sills." They're older when they say their first word, their sentences are shorter and baby talk persists longer that it does with other children, ' he says. "They are also known to develop a secret language they use to communicate with one another." Hay has found that this exclusive language is usually the result of one twin omitting letters and syllables as he or she hurries to get a message across before the other one interrupts." In a sense their language is very adaptive to their own environment, but unfortunately, maladaptive to other situations," he says. "Until recently it was believed language problems gradually diminished until around the time of starting school for all children. But now it appears that twins in particular develop a shaky foundation in this area that has to be corrected early."
Problems with Twin Boys
Hay has also found that "mirror image" identical twin boys are especially at a loss in trying to pick up language skills in school. They are at a double disadvantage, he notes, because boys are normally slower at language acquisition than girls are. According to Hay, as many as 90 percent of the "mirror image" boys at primary level had some reading problems while 23 percent were seriously learning-disabled. But environmental factors contribute even more heavily to twins' troubles, Hay believes. Identical twins, his research shows, have cause to challenge their parents' fairness. Parents tend to lavish more time and attention on the first-born twin, who is o

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