IN THIS ISSUE
In This Issue
Early Life Experiences
Parents' stress leaves lasting marks on children's genes, according to Essex et al. (p. 58) in their longitudinal study of epigenetics, the expression of genes, which differs from the underlying sequence of DNA. A central part of epigenetics is methylation, in which a chemical group attaches to parts of the DNA in a process that acts like a dimmer switch on gene function in response to social and physical environments. Researchers measured methylation patterns in the cheek-cell DNA of more than a hundred 15-year-olds, then compared them to information gathered when the children were infants and preschoolers. Their parents reported on their own stress levels, including depression, family-expressed anger, and stress related to parenting and finances. Families represented a range of economic backgrounds and were primarily White; most parents were married. Results show that exposure to parents' day-to-day stress in early childhood can predict changes in DNA expression that can be seen in adolescence, with differences by gender and children's age.
Early life experience plays a crucial role in human development, but how it does so is not well understood. Early life experience could result in changes in the chemical coating of our genes, which affect how the genes function and serve as a mechanism for lifelong adaptation of genomes to the environment. Szyf and Bick (p. 49) provide an overview of a specific epigenetic process, DNA methylation, and present evidence from human and animal research supporting connections among early life stress, changes in DNA methylation, and phenotypic variation. Understanding the processes involved will shed light on issues of risk and resiliency.
Autism and Genetics
What causes autism? Although genetic analyses suggest a strong hereditary component of autism spectrum disorders (ASDs), genes can't be used to uniquely diagnose autism and environmental factors may play a role. Hu (p. 89) reviews the multifactorial nature of ASD and how different genome-wide (or genomic) approaches contribute to our understanding of autism, exploring genetics, epigenetics, gene expression, and environmental influence. Using integrative genomics may allow the development of a systems-level understanding of ASDs, which could in turn inform the development of targets and interventions for those affected by this disorder—1 in 88 people, according to the most recent data.
Efforts to understand the genetic basis of ASDs have moved forward considerably, but progress has been hampered by the genetic complexity of the disorders. A potentially productive strategy for reducing this complexity is to target endophenotypes, simpler biologically based measures that may involve fewer genes and constitute a more homogenous sample. Connolly, Glessner, and Hakonarson (p. 17) examined more than 500,000 genetic markers in more than 2,100 children (mean age of 8) from the Autism Genetic Resource Exchange and more than a million markers in more than 1,200 children (mean age of 7) from the Autism Genome Project to find eight significant associations. Their preliminary findings may help prioritize efforts to understand the genetic causes of autism.
Genetic Foundations, New Technologies
In the last few years, the ability to identify genetic abnormalities associated with a range of childhood disabilities and birth defects has dramatically improved due to chromosomal microarray analysis (CMA). CMA allows for the detection of any deleted (missing segments) or duplicated (extra segments) of a child's genome. Beaudet (p. 121) reviews CMA as a tool in diagnosing such disabilities as autism, schizophrenia, attention deficit hyperactivity disorder, and Tourette syndrome. Using such a tool to identify genetic causes allows for accurate diagnosis, counseling, and treatment.
Since the completion of the Human Genome Project, researchers have studied structural variation in human DNA and its impact on human development. Of late, they have focused on issues of the genome's activity and its regulation throughout development. In their review of the latter, Naumova, Lee, Rychkov, Vlasova, and Grigorenko (p. 76) highlight central concepts and methods used in studies of gene expression, with a focus on the brain. Among the topics addressed are the age-related transformation of the transcriptome—the set of RNA molecules that the genome produces in a cell or tissue at once—from a developmental perspective. As new technologies make studies of the transcriptome affordable, it's anticipated that such work will soon be incorporated into the portfolio of developmental research.
Powerful new gene-finding techniques have begun to be used to identify genes responsible for the widespread influence of genetics in children's development. Many genes are involved, the techniques suggest, each with very small effects that are difficult to detect. As a result, the genes found so far account for but a small fraction of the known heritability of traits—known as the missing heritability problem. Plomin (p. 104) describes three new advances in gene-finding techniques, which have revolutionized gene-finding research and identified many genes that contribute to the heritability of behavioral dimensions and disorders. Since the biggest effects of these genes are very small, suggesting that many genes are needed to explain heritability, the review describes ideas for finding the missing heritability.
Structural variation of the human genome sequence is the insertion, deletion, or rearrangement of stretches of DNA sequence sized from around one thousand to millions of base pairs. Over the past few years, structural variation has been shown to be far more common in human genomes than previously thought; it's also emerging that many genomic structural variants can be associated with atypical outcomes for child development. Together, these two phenomena form the foundation for the expectation that genomic structural variation will emerge as a significant factor in shaping the phenotypes of child development even within the normal range. Zhang et al. (p. 34) provide an overview of structural variation in the human genome sequence, describing the novel genomics technologies that are changing the way structural variation is studied, and providing examples of genomic structural variations that affect child development.
Pulling an All-Nighter
Regardless of how much a high school student generally studies each day, if that student sacrifices sleep in order to study more than usual, he or she is more likely to have academic problems the following day. And because students tend to increasingly sacrifice sleep time for studying in the latter years of high school, this negative dynamic becomes more and more prevalent over time. Those are the conclusions reached by Gillen-O'Neel, Huynh, and Fuligni (p. 133) in a longitudinal study of 535 high school students of a range of socioeconomic and ethnic backgrounds that focused on daily and yearly variations of sleep. The findings don't suggest that teens spend less time studying. However, they do suggest that students who sacrifice sleep on a given night to study are more likely to have academic problems the next day, even if that sacrifice was made for extra study time.
Ethnic and Political Violence
Ethnic and political violence in the Middle East can increase violence in families, schools, and communities, which can in turn boost children's aggressiveness, especially among 8-year-olds. That's the conclusion reached by Boxer et al. (p. 163) in a longitudinal study that examined about 1,500 children and their parents from Palestinian Arab families, Israeli Jewish families, and Israeli Arab families. Palestinian children were at the greatest risk for exposure to violence and showed the highest level of aggressive behavior. Boys were at greater risk than girls for all forms of exposure to violence and for aggression. And the oldest children tended to experience more violence than the younger ones, but they weren't uniformly more aggressive. By helping us understand how political struggles can spill over into the everyday lives of families and children, the study can inform intervention efforts.
Most low-income children whose mothers worked in the first 2 years after they were born—especially those whose moms worked in the first 9 months—had better emotional and behavioral health than their peers whose mothers didn't work, according to a study by Coley and Lombardi (p. 178). The benefits showed up whether moms worked full-time or part-time, were greater for African American children than Hispanic children, and were greater for children in informal child care (such as relative care) than those in formal child-care centers. The longitudinal study used data from the Three-City Study, examining 444 infants from Boston, Chicago, and San Antonio until age 7 and collecting information from their mothers. One of the first studies to look at the effects of moms working in exclusively low-income families, its positive conclusions run counter to studies of White and middle-class children.
The U.S. welfare system was reformed about 20 years ago to require participants to be employed or engaged in employment-related activities like job training or further education. Gassman-Pines, Godfrey, and Yoshikawa (p. 198) examined whether children' development improved when welfare mothers received the type of employment-related activities they preferred. They looked at 1,365 families with children between 3 and 5 that received welfare benefits in three U.S. cities as part of the National Evaluation of Welfare-to-Work Strategies, an early 1990s program that assigned moms by lottery to either employment or education programs. Five years later, teachers rated the children's social behavior as more positive when mothers received educational services, but only among mothers with strong preferences for those services. When moms' wishes for their own education were different from the program they were assigned to (e.g., when moms who wanted more education were assigned to an employment program), their children were said by their teachers to have worse behavior. The findings have implications for welfare policy.
Young children in lower income families who live in high-cost areas don't do as well academically as their counterparts in low-cost areas, according to a new study by Chien and Mistry (p. 209). Researchers used data from the Early Childhood Longitudinal Study-Kindergarten Cohort, a nationally representative sample of more than 17,500 children at more than 2,000 schools who started kindergarten in 1998. Among families with incomes below 300 per cent of the federal poverty threshold—below $66,339 for a family of four—living in a region with a higher cost of living was related to lower academic achievement in first grade, the study finds. This is the first study to show that income isn't enough; cost-of-living differences also matter for children's development, particularly for children from lower income families.
Babies in Action
Researchers have long studied infants' perceptions of safe and risky ground by observing their willingness to cross a visual cliff, a large drop-off covered with a solid glass surface. In crawling, infants grow more likely to avoid the apparent drop-off, leading researchers to conclude that they gain a fear of heights. Kretch and Adolph (p. 226) studied about 50 children, including 12-month-old experienced crawlers, 12-month-old novice walkers, and 18-month-old experienced walkers. They find that although infants learn to avoid the drop-off while crawling, this knowledge doesn't transfer to walking. This suggests that what infants learn is to perceive the limits of their ability to crawl or walk, not a generalized fear of heights. The findings have implications for understanding children's development as well as for infants' safety.
In the physical world, the “how” and “where” of an action are inextricably linked: As a ball rolls down a hill, the rolling motion (the “how”) and the downward motion (the “where”) happen together at the same time. But in human language, the “how” and the “where” are separated, as in the sentence, The ball rolls down the hill. Pulverman, Song, Pruden, Golinkoff, and Hirsh-Pasek (p. 241) examined whether almost fifty 7- and 8-month-olds noticed the “how” and “where” of actions as they watched a video presenting different actions, and whether they perceived these two action components as independent of one another. Findings: By the time babies learn how to crawl, they can tell the difference between the two action components, with girls slightly ahead of boys.
Ingroup Versus Outgroup
Children exhibit a subtle bias toward helping same-race versus other-race children, according to a study by Weller and Lagattuta (p. 253) that looked at about 75 European Americans aged 5–13. The children listened to dilemmas in which the desires of the central character conflicted with the needs of an unfamiliar child, and in which helping the central character required a sacrifice of a planned, fun activity. Racial bias across all age groups appeared in children's predictions that most children would feel better helping and worse not helping same-race versus other-race children in need. However, racial bias didn't appear in children's predictions of whether or not most children would help. The findings offer insights into the motivations underlying children's altruistic choices in daily life.
Across two different cultures, children prefer to learn from people who agree with one another, especially when they belong to the same social group as the children. That's the conclusion of two studies by Chen, Corriveau, and Harris (p. 269) that looked at how 4- to 7-year-olds from the United States and Taiwan weigh consensus cues and social/racial/ethnic group membership cues when learning new information. The studies, of more than 130 European American and Taiwanese children, find that although children favored claims made by a consensus, this preference depended on the racial/ethnic composition of the informants. When consensus members were of the same race/ethnicity as the children, they consistently preferred the information provided by the consensus, even after the consensus no longer existed. But when consensus members were of a different race/ethnicity, the initial preference for the consensus was lost when the consensus dispersed.
Infants' relationships with their caregivers, or their early attachment bonds, are key for children's adjustment. Kochanska and Kim (p. 283) looked at about 100 primarily White children when they were 1, then studied them again when they were 6 and 8 when teachers, parents, and the children themselves answered questions on their behavior. They examined ties between the quality of the infants' attachment with both moms and dads (who have assumed increasing roles as caregivers in many families), on the one hand, and with children's adjustment in middle childhood, on the other. Children who had been insecure with both parents were at a substantially higher risk for behavior problems than those who had been secure with at least one parent. But security with either parent could offset such risks, while security with both parents, surprisingly, conferred no additional benefits. By including dads as well as moms in their research, this study addresses a gap in the field and has practical implications for many families.
Young children from low-income families who respond in fearful, insecure ways to conflicts between their parents are more likely to have behavior problems because they have difficulty achieving such developmental milestones as regulating their emotions, asserting autonomy, and resourcefully solving problems. That's what Davies, Manning, and Cicchetti (p. 297) find in their longitudinal study of an ethnically diverse group of about 200 mothers and their preschoolers, beginning when the children were 2. The findings suggest that for children living in poverty, fears about parents' conflict can take a toll on children as early as the toddler period. The study can inform prevention and early intervention programs.
Although most children produce their first spatial prepositions (words like over, under, and around) before their second birthdays, little is known about when and how children make sense of the actions and events that those terms refer to. Because most spatial prepositions in English encode a figure's path (“The cow jumped over the moon”), the ability to detect trajectory changes is fundamental to learning these terms, as is the ability to look for similarities across actions and group them into categories. In three studies, Pruden, Roseberry, Göksun, Hirsh-Pasek, and Golinkoff (p. 331) investigated how more than a hundred primarily White and middle-class infants aged 7–9 months and 10–12 months made sense of a figure's path when other features of the event—such as how the figure is moving—changed. Taken together, these studies provide the first evidence that infants can form categories of paths when witnessing dynamic events, a component that's important to learning spatial prepositions.
In the early stages of language development, young children can learn both words and symbolic gestures—sometimes called baby signs—as names for things. They often use words and symbolic gestures together until they have enough vocabulary that they no longer have to rely on symbolic gestures. Suanda and Namy (p. 143) looked at more than sixty 18-month-olds during a period of development when words and gestures are closely linked and seem to serve the same communication functions. They find that young children interpret words and symbolic gestures differently, depending on the task involved, using smart learning strategies for words, but not for gestures. For example, if children see two things, one that they know (a bowl) and one that they don't (a whisk), children appear to use their knowledge of the word bowl to infer that a new word, whisk, refers to the whisk instead of the bowl. Children don't use a similar learning strategy in gesture learning. The results may inform the development of diagnostic tools for children with language delays and disorders.
By the time they're 3, English and French children can cope with variation in how words are pronounced in sentences in their native languages. That's what Skoruppa, Mani and Peperkamp (p. 313) find in their study of whether more than 70 preschoolers (aged 2½–3) take into account variability caused by assimilations when listening to words in sentences. Assimilations are processes by which the pronunciation of one sound becomes more similar to that of the sounds surrounding it, making the whole sentence easier to say (e.g., ten pounds can turn into tem pounds). English toddlers took assimilations into account from age 3 when hearing phrases in their native language, as did French toddlers when hearing phrases in their native language; this is earlier than previously reported. But French toddlers didn't compensate for a hypothetical nonnative assimilation process that doesn't exist in French, suggesting that processing of phonological variation has already adapted to the particularities of the native language by age 3.
Emotion and Cognition
Many factors in early life influence individuals' cognitive development and academic achievement. Bornstein, Hahn, and Wolke (p. 154) took a longitudinal look at about 550 children from infancy to adolescence who were part of the Avon Longitudinal Study of Parents and Children to determine which factors relate to later achievement. Findings: Infant abilities, proclivities, and experiences shape toddlers' and children's cognitive development, which in turn influence adolescents' academic achievement. By thinking of cognition from infancy in terms of developmental systems and cascades, the study sheds light on the nature and structure of intelligence and the multiple roots of academic achievement.
Early emotional skills affect how children perform cognitively later on in development, according to a longitudinal study by Blankson et al. (p. 346) that considered preschoolers' emotional and cognitive development together. The study examined more than 250 children of diverse backgrounds at age 3 and a year later, at 4, focusing on emotional control, cognitive control, emotion understanding, and cognitive understanding. By understanding the developmental links between emotional and cognitive processes, this research can help us better understand the interplay across domains that are often studied independently. The study also highlights the value of fostering early emotional development in preschool and other early intervention programs.
Teaching children strategies to regulate sad emotions improves their memory for educational information, according to Davis and Levine (p. 361), who studied about 125 children aged 6–13. When the children were taught to use reappraisal (which encouraged them to think of a negative event as unimportant or consider how things could get better), they were able to focus their attention on details of educational information that was later presented to them and remember that information better. Since children's capacity for attention is limited and emotions can divert attention from information, this study can inform efforts to help children regulate their feelings to give them an intellectual advantage in learning.
The Role of the Bystander
Some 13% of American students report being physically bullied, and 37% say they've been verbally bullied. In most cases of bullying, there are bystanders. Barhight, Hubbard, and Hyde (p. 375) asked why some intervene to try to stop the bullying while others don't. Unlike in other studies, they measured the heart rates of almost 80 fourth and fifth graders as the children watched videos of bullying and asked the children to rate their emotions; they also asked about 775 peers which children were most likely to intervene when someone was being bullied. Findings: About 43% of the children responded to the videos emotionally, becoming upset; the other 57% weren't distressed. The children who were emotionally upset when they witnessed someone bullying another child were more likely to intervene to try to help someone who was being victimized than the children who weren't upset. The results can inform the development of antibullying programs.