What is the main finding of Hart and Risleys 1995 study on the effect of socioeconomic status on childrens linguistic experiences?

Early life experiences have pervasive long-term effects on children's psychological and behavioural development. Although early life experiences are likely to be too broad and too idiosyncratic to be captured and studied in full (Plomin & Daniels, 1987), key influences have been identified that shape children's developmental trajectories. They range from feeding practices for newborns (e.g. Victora et al., 2016; Yorifuji et al., 2014) to parents' child-directed language (e.g. Hart & Risley, 1995; Hoff, 2003) to families' socio-economic status (SES; Bradley & Corwyn, 2002) and their wider neighbourhoods and local communities (e.g. Davis, Haworth, Lewis, & Plomin, 2012; Flouri, Midouhas, & Joshi, 2015). Associations between early life experiences and psychological and behavioural development become evident already in the first year of life (e.g. Hurt & Betancourt, 2017; von Stumm & Plomin, 2015).

Previous research on early life environments typically relied on one-time observer reports that are either collected from the parents (e.g. Haworth, Davis, & Plomin, 2013) or by trained researchers who visit the families' homes (e.g. Hart & Risley, 1995). For example, researchers or parents may complete the Confusion, Hubbub and Order Scale (CHAOS; Matheny, Wachs, Ludwig, & Phillips, 1995), which assesses the level of confusion and disorganization in the child’s home environment and is recognized as a marker of family SES, or the Food Frequency Questionnaire (FFQ; e.g. Block et al., 1986) that obtains frequency and portion size information about people's food and beverage consumption. The scales are completed once in time for each family or study participant, under the assumption that they capture phenomena that are relatively static across time. A logical consequence of this measurement approach is focusing on differences in experiences that occur between families (e.g. Bradley & Corwyn, 2002; Hart & Risley, 1995), because within-family variations in early life experiences cannot be studied with one-time assessments.

Early life experiences emerge from the interplay of the physical and psychological environments that parents and other caregivers provide and the child's own psychological and behavioural function (Bronfenbrenner & Ceci, 1994). Because early life experiences are dynamic, developmental phenomena themselves, they do not vary exclusively between individuals or families. For example, a recent study of children's exposure to language in the family home found that the number of adult words that children heard over the course of a day varied as much within as between families (D’Apice & von Stumm, 2017), although previous research focused only on between-family differences in language exposure (e.g. Hart & Risley, 1995; Hoff, 2003). For the vast majority of the experiences that shape infants' early life development, the extent to which differences occur within compared to those between families is yet unknown. As a result, little attention has been paid to the effects of within-family variations on children's psychological and behavioural outcomes, while a large body of empirical evidence substantiates the role of between-family differences for development.

Studying within-family variations in early life experiences requires repeated assessments or observations that take place close in time to one another (i.e. hours or days). Traditional experience-sampling methods, like diary studies that ask participants to document either in paper-pen mode or through a computer survey their experiences as they go through life, are now common practice in many areas of developmental psychology (e.g. Hektner, 2012; Hoppmann & Riediger, 2009) but they are difficult to implement in families that look after a newborn, often in addition to caring for the baby's older siblings. However, these difficulties can be at least partly overcome through smartphone-based assessments that collect data with specifically designed applications (apps; Harari et al., 2016; Wrzus & Mehl, 2015). Today, 85% of British adults are estimated to own a smartphone (Deloitte, 2017), which offers an unprecedented opportunity to study psychological and behavioural phenomena in the wider population in real-time, including in infancy and early childhood.

The current study reports a preliminary test of using a smartphone app to observe across three weeks four key experiences that inform infants' early life, including mothers' and babies' sleep and dietary patterns, as well as mothers' wellbeing and the support that they receive as mothers. We focused on these four domains, because they (a) capture typical daily experiences in the lives of mothers and their babies, and (b) have been shown to affect children's developmental trajectories (e.g. Birch & Fisher, 1998; Davidson et al., 1998; Hiscock, Bayer, Hampton, Ukoumunne, & Wake, 2008; Muzik & Borovska, 2010). The aim of this research was threefold. First, we wanted to explore if smartphone apps are practicable for conducting experience-sampling studies with infants. To this end, we recruited a sample of mothers with infants aged 2 to 15 weeks to complete 12 app alerts over the course of three weeks. App alerts either assessed mothers' and babies' sleep and dietary patterns (3 times per week; 9 assessments overall), or mothers' wellbeing and support that they received (once per week; 3 assessments overall). Afterwards, mothers reported any difficulties, likes and dislikes they had experienced when using the app. Second, we sought to test the extent to which early life experiences varied within compared to between families. Specifically, we estimated within- and between-family variances in mothers' dietary intake, including the consumption of fish, fruit, alcohol and dietary supplements, and in mothers' wellbeing, the support that they received, and their sleeping patterns. In addition, we tested within- and between-family differences in the number of times that babies were fed and how many hours they slept. These analyses explored if early life experiences varied within families and thus, should not be exclusively treated as between-family differences. Finally, we wanted to provide preliminary evidence for the hypothesis that within-family variations that occur across assessments are meaningfully associated with concurrent variations in mothers' and babies' psychological and behavioural outcomes. To reliably detect such coupling effects, at least 10 but preferably more repeated assessments are recommended (Wang & Grimm, 2012), suggesting that the current study is somewhat underpowered (i.e. maximum number of assessments was 9). We therefore tested two simple associations between the within-family variances, rather than modelling a more complex nexus of relationships. The first focused on the relationship between mothers' quality of sleep, the number of hours that they slept, and the number of times that they attended to their newborn infant during the night. Previous research has shown that the goodness of fit between mothers' and infants' sleep predicts maternal depression and attachment security (Newland, Parade, Dickstein, & Seifer, 2016), and that the frequency with which mothers attend to their babies informs their subjective sleep quality (Gress et al., 2010). Here, we predicted that mothers, who slept more hours and attended to their baby fewer times compared to other mothers (i.e. between-mother effects), would report better sleep quality. We also predicted that mothers would report better sleep quality on days when they had slept more hours and attended to their baby fewer times during the night compared to other days (i.e. within-mother effects). The second test focused on predicting babies' differences in the number of hours that they slept across assessments from the differences in mothers' sleep duration. Sleep has been shown to facilitate the consolidation of declarative memory in infants (Seehagen, Konrad, Herbert, & Schneider, 2015) and creates semantic knowledge from individual episodic experiences (Friedrich, Wilhelm, Born, & Friedrich, 2015). In short, infants' sleep appears to be a key influence for their brain development and learning. We predicted that babies, whose mothers reported sleeping for longer durations, would also have slept longer hours than babies of mothers who had slept fewer hours (i.e. between-family difference). In addition, we predicted that babies would have slept longer on days in which their mothers reported having slept more hours, compared to other days (i.e. within-family variations). Our study design does not allow inferring the direction of causation -- it is just as plausible that mothers sleep longer on days that their babies sleep longer as vice versa -- but serves merely as a proof of concept.

Sample

Fifty-three mothers of infants (30 boys and 23 girls) completed all parts of this research. Mothers’ ages ranged from 24.49 to 42.38 years (mean = 34.46 years; SD = 4.35 years), and their infants’ ages ranged from 0.48 to 3.60 months (mean age = 1.7 months, SD = 0.96 months). All mothers were in a relationship (mean duration = 7.87 years; SD = 3.48 years; range 1–17 years); most were married (77.36%); and all except one lived with their partner. Most mothers had one (N = 22) or two (N = 27)

Practicability of smartphone app

A total of fifty-seven mothers completed the study's online survey and were eligible to participate in the app-based assessment. Two mothers did not download the app for unknown reasons, and another two were excluded from the analyses, because they did not complete the app alerts for the study duration of 3 weeks of the app alerts (i.e. 7% attrition). Of the 53 participating mothers, 39 (74%) completed the study's online exit survey. The majority of these mothers indicated that the app’s

Discussion

Early life experiences, ranging from feeding practices in newborns to parents' child-directed language, have pervasive effects on children's psychological and behavioural development (e.g. Bradley & Corwyn, 2002; Hart & Risley, 1995). However, traditional research methods assessed early life experiences 'once in time' as static entities rather than as the dynamic processes that they are. As a result, much more is currently known about the developmental consequences of differences that occur

Conflict of interest statement

We declare no conflict of interest with regard to this manuscript or the research described in it.

Acknowledgements

This work was supported by the Imagination Institute, funded by the John Templeton Foundation [grant number II-RFP-15-03]. SvS is the recipient of a Jacobs Foundation Research Fellowship award (2017-2019). We thank Professor Alice Gregory for her advice on items for assessing mothers’ and infants’ sleep, and PSYT (www.psyt.co.uk) for their help with the iPhone app design and implementation.

Recommended articles (6)