By: Brittany Ann Stinson
Young children demonstrate high variability in rates of language growth and development (Fenson, 1994). This commonly ranges from not being able to produce words until the second birthday while some infants are able to start speaking before 12 months (Fenson, 2007).
As slow growth can predict difficulties in school later on, a general awareness of signs in language growth delay and its potential causal factors may aid in abating negative outcomes. To an extent, genetics are capable of explaining differential rates of language development from child to child, however environmental factors demonstrate a significant ability to steer these outcomes–such as differences in socioeconomic status (Fenson,2007) (SES) .
This can set children from lower SES backgrounds behind by the time they begin formal schooling–resulting in lower cognitive skills than those who come from more well off families as they begin kindergarten (Bereiter, 1966). This news is not new, however the research group attempts to answer the question as to when these differences begin to emerge. This initiates a cascade that can alter their outcomes into adulthood–SES differences in language proficiency still remain pronounced into adulthood (Pakulak, 2010).
A study conducted at Stanford University sought to investigate the development of language processing efficiency and its relationship to vocabulary in families from English-speaking backgrounds of varying SES. Children were followed from the age of 18 to 24 months. Researchers tracked changes in processing efficiency and vocabulary learning and framed their findings in the context of SES differences.
They found that there were already significant disparities in vocabulary and language processing efficiency at 18 months when comparing infant from higher and lower SES families. By the time children reached 24 months, there was a 6-month gap in language processing skills between SES groups (Weisleder, 2013).
In a follow-up study, researchers traced child-directed speech among infants in Spanish-speaking families of low SES in order to assess its influence on the child’s real-time language processing and vocabulary learning skills.The researchers conducted audio recordings over the course of a normal day when infants were 19 months old to record both overhead and child-directed speech. Overheard vs. child-directed speech were differentiated as follows: native Spanish speakers listened to recordings and classified each 5-minute segment as containing speech that was predominantly child-directed or overheard. Number of “word tokens” spoken in each segment divided by the duration of the recording served as the measure for each type of speech. The number of “speech-like vocalizations” produced by the child divided by duration of the recording served as the measure for child vocalizations. From these figures vocalizations per hour and per 10-hour waking day were estimated (Burger, 2011).
Results showed that within the low-SES families, there was a high variability between child-directed speech spoken in the household, ranging from nearly 29,000 to less than 2,000 words over 10 hours. Those who heard more child-directed speech at 19 months had larger expressive vocabularies– the words that a person is able to produces, this is in contrast to receptive vocabulary which are words that a person comprehends and can respond to, but not necessarily produce (Burger, 2011)– by 24 months of age. Overheard speech was found to be unrelated to vocabulary size outcomes. Mediation analyses conducted and revealed that language processing efficiency explained the effect of child-directed speech on expressive vocabulary.
This research highlights the importance of child-directed speech specifically, processing efficiency mediating effect on vocabulary, and the snowball effect of a late start. Lower-SES parents likely need to work more hours to support their families, may not be able to afford reliable childcare and as a result are spending less time at home talking to their children (Chen, 2018). These factors can set infants behind before they even reach the starting gate, creating challenges for children that follow them throughout their educational careers and further exacerbating socioeconomic disparities. In order to overcome these inequities, interventions must be made in infancy before the vocabulary gap widens further and influences their long-term trajectories.
Bereiter, Engelmann. Teaching disadvantaged children in the preschool. Published online 1966.
Burger A, Chong I. Receptive vocabulary. In: Goldstein S, Naglieri JA, eds. Encyclopedia of Child Behavior and Development. Springer US; 2011:1231-1231. doi:10.1007/978-0-387-79061-9_2359.
Chen Q, Kong Y, Gao W, Mo L. Effects of socioeconomic status, parent–child relationship, and learning motivation on reading ability. Front Psychol. 2018;9:1297. doi:10.3389/fpsyg.2018.01297
Fenson L, Dale PS, Reznick JS, Bates E, Thal DJ, Pethick SJ. Variability in early communicative development. Monogr Soc Res Child Dev. 1994;59(5):1-173; discussion 174-185.
Fenson L. MacArthur-Bates Communicative Development Inventories: User’s Guide and Technical Manual. 2nd ed. Paul H. Brookes Pub. Co.; 2007.
Oliver BR, Plomin R. Twins’ early development study (Teds): a multivariate, longitudinal genetic investigation of language, cognition and behavior problems from childhood through adolescence. Twin Res Hum Genet. 2007;10(1):96-105. doi:10.1375/twin.10.1.96
Pakulak E, Neville HJ. Proficiency differences in syntactic processing of monolingual native speakers indexed by event-related potentials. J Cogn Neurosci. 2010;22(12):2728-2744. doi:10.1162/jocn.2009.21393
Weisleder A, Fernald A. Talking to children matters: early language experience strengthens processing and builds vocabulary. Psychol Sci. 2013;24(11):2143-2152. doi:10.1177/0956797613488145
Brittany is a senior at Stanford University studying Human Biology. She cares about how socio economic disparities influence barriers to health and well-being.