This study is the first, to our knowledge, to have longitudinally assessed associations between media exposure in infancy and subsequent developmental outcomes in children from US families with low SES. Regarding our first hypothesis, total duration of media exposure at age 6 months predicted lower cognitive and language development at age 14 months. More important, children with 60 minutes of media exposure had approximately one-third SD lower developmental scores in both domains compared with those who had no exposure. Although children with the longest durations of media exposure had adjusted developmental scores in the normal range, the differences found are likely to be important at the population level.34,35
Regarding our second hypothesis, exposure to media with older child/adult–oriented content at age 6 months was associated with adverse developmental outcomes at age 14 months. In contrast, significant associations in either direction were not found for exposure to educational and noneducational young child–oriented content. Taken together, our findings provide strong evidence in support of the American Academy of Pediatrics recommendations of no media exposure prior to age 2 years. In demonstrating adverse effects of older child/adult–oriented media, these findings suggest that even media likely not focused on by very young children36,37
may have adverse effects, possibly owing to interference with interactions and play.38,39
In demonstrating lack of benefit related to educational media exposure in infancy, these findings contradict industry claims40
and provide further support for these recommendations.
In documenting adverse associations between overall media exposure in infancy and development at age 14 months, this study has provided an important addition to the existing literature. Two studies performed in Thailand have investigated the effect of media exposure in infancy on the development of toddlers from families with low SES, with only 1 finding positive results. Chonchaiya and Pruksananonda41
performed a case-control study that found that children exposed to 2 hours or more of television daily prior to age 12 months were 6 times more likely to have language delay. Ruangdaraganon et al42
performed a longitudinal study that did not find associations between media exposure and development; however, only 8% of the sample had developmental delay, limiting the authors’ power to find associations. In addition, 3 longitudinal studies of associations between media and development in US populations that are not economically disadvantaged have been published. In an analysis of National Longitudinal Study of Youth data, Zimmerman and Christakis13
found that average viewing prior to age 3 years was negatively associated with cognitive outcomes at age 6 years. In a US longitudinal analysis of predominantly white, Mid-western families with relatively high levels of education and income, cumulative prior media exposure was associated with reduced vocabulary at 30 months.43
However, in a longitudinal analysis of families in Massachusetts with similar sociodemographic characteristics who are not economically disadvantaged, no associations were found between media exposure prior to age 2 years and language development at 36 months.44
Our study, the first to longitudinally study effects of media exposure on development in the United States, suggests real possibility for harm in the vulnerable population of families with low SES.
A strength of our present study was the use of detailed media diaries to quantify duration based on content. Based on these diaries, exposure in infancy to older child/adult–oriented content not appropriate for young children was specifically associated with adverse developmental outcomes. Previous studies in older children have shown adverse effects in association with developmentally inappropriate content, including associations between media violence exposure in elementary school and aggressive behavior12
and associations between older child/adult–oriented media content and externalizing behaviors21
in older toddlers. Our present findings extend these associations to very young infants.
Regarding educational content, we found limited associations (positive or negative) with developmental outcomes. Our single finding, a nonsignificant trend, suggested the possibility of an adverse association between educational media exposure and overall language development after adjusting for exposure to other content. Although exposure to educational content at the age of school entry has been shown to have potentially beneficial effects,20,45
two prior studies of infants and toddlers from families that are not economically disadvantaged have suggested the possibility of adverse effects. In a cross-sectional study, Zimmerman et al46
found exposure to educational DVDs for infants such as Baby Einstein
to be associated with decreased concurrent vocabulary in 8- to 16-month-old children. In a longitudinal study, Linebarger and Walker43
found that exposure beginning in infancy to some educational programs (Teletubbies, Sesame Street,
and Barney and Friends)
was associated with reduced later vocabulary at age 30 months, whereas other programs (Dora the Explorer, Blue’s Clues,
and Dragon Tales
) were associated with enhanced vocabulary. In contrast, experimental studies36,47–50
have consistently shown reduced learning from video compared with live models, which may be owing to formal characteristics that elicit attention but are difficult for infants to understand.51
In finding lack of positive effects resulting from exposure to educational content, our study does not support development of even educational media for infants.
There are 3 potential mechanisms for media-associated adverse effects on very young children’s development. First, a number of studies have shown reductions in parent-child interactions in association with increased media, including reduced audible language,15
and engagement with the child.38
Other studies have suggested potential displacement of parent-child shared reading and playing together with toys,39,52
activities critical to young children’s development. Second, exposure to media in very young children has been shown to interfere with children’s play activities.39
Third, specific characteristics of media exposure such as rapid scene changes have been hypothesized to have direct, adverse effects on the developing brain.7,36
The first of these mechanisms, reduced interactions, is likely to be especially important in families with low SES, in which children are at increased risk of developmental delay in association with less parental language being directed at them.11
Another important finding relates to characterization of media exposure in children from families with low SES. Our findings are consistent with prior population-based studies in infancy, which have shown substantial exposure as early as age 6 months,53
with increased exposure related to low maternal education.8
However, our finding that the greatest media exposure for infants from families with low SES is to older child/adult–oriented content contrasts with prior studies showing educational content to make up the majority of exposure in infancy.53
Our findings underscore the increased risks experienced by children from families with low SES related to early development in the context of greater overall exposure to media and exposure to media less likely to have educational content. Even small effect sizes as noted in this study, with a 50.0% increase in media exposure associated with a 0.5-point decrease in PLS-4 total score, are likely to be important regarding families with low SES, who are already at risk.34,35
This study has some limitations. First, although the use of media diaries allowed the collection of detailed information regarding content, we must acknowledge the possibility that data collected via this assessment tool may underestimate quantity of media in the home and only covers 1 typical day.54
Second, there was limited exposure to young child–oriented noneducational media in this sample, which reduced our ability to draw conclusions about its effect. Regarding young child–oriented educational media, most of the exposure was to preschool-oriented educational media, and there was limited exposure to infant-directed media such as Baby Einstein
, which prevented us from analyzing this exposure separately. Third, lower effects on expressive compared with receptive language tests may reflect limited expressive language at age 14 months; it is possible that greater effects on expressive language might be seen for older children. Fourth, our results apply to exposure in infants from families with low SES, primarily from a Latino immigrant background, and may not be generalizable to children in families with greater economic resources. Finally, our results may be specific for the infant–early toddler period studied, given rapid changes in development and changes in content of exposure over time, with educational television representing a greater proportion of exposure.53
In conclusion, overall exposure and exposure to older child/adult–oriented content were associated with lower levels of cognitive and language development at age 14 months. Findings from this study provide strong support for the American Academy of Pediatrics recommendation of no media exposure before age 2 years. These findings also cast doubt on the potential for benefit from educational programming in infancy. However, more research is needed regarding what would constitute educational programming during early childhood before definite conclusions can be reached. Given the substantial amount of exposure beginning in early infancy in families with low SES, whose children are at greatest risk for adverse developmental outcomes, these findings suggest that media exposure represents a substantial public health problem. Advocacy efforts and public health interventions will be necessary to reduce exposure and optimize developmental outcomes.