Growing up in Scotland: changes in child cognitive ability in the pre-school years

CHAPTER 1: INTRODUCTION

1.1 Background

Analysis in this report examines differences in cognitive ability at age 3 and 5 years amongst children with different social background characteristics and seeks to identify which circumstances and experiences contribute to change in the cognitive ability of children in lower (and higher) socio-economic groups in the pre-school period. In so doing, the report aims to identify factors which policy could usefully affect in order to maximise children's cognitive ability ahead of entering school and help narrow the considerable difference in ability between children from more and less advantaged circumstances.

To date, research from the Growing Up in Scotland ( GUS) study has demonstrated stark variation in cognitive ability at age 3 amongst children from different backgrounds. Bromley (2009) found that children from less advantaged families were outperformed by their more affluent counterparts and noted worse ability in particular amongst boys, children with younger mothers, those from lone parent families, children with early developmental difficulties and those with a low birth weight. Bradshaw and Wasoff (2009) further revealed a relationship between early experience of childcare and cognitive ability, with children who experienced between 17 and 40 hours of non-parental childcare a week shown to have better vocabulary acquisition at age 3. Considerable other research has linked childcare and pre-school experiences to cognitive ability, indicating, for example, that as compared to no experience of centre-based care or pre-school education, children with any experience tend to have improved language and cognitive skills (Sylva, 2009; Butt et al, 2007; Magnuson et al, 2010). The quality of provision is the key element of the care and pre-school experience associated with making the greatest impact on on intellectual and cognitive development (Sylva et al, 2009). Experiences in the home are also important, as analysis from GUS has shown. Both Bromley (2009) and Melhuish (2010) have demonstrated a positive relationship between the amount of home learning activities a child experiences and their level of cognitive ability. In other analysis poor maternal mental health and experience of poverty have been linked to lower cognitive scores (Marryat and Martin, 2010; Barnes et al, 2010).

A range of other research has explored whether these gaps in ability persist as children age. Feinstein (2000) for example, found that children of educated or wealthy parents who scored poorly in early tests (at 22 or 42 months), had a tendency to catch up whereas children of disadvantaged parents who scored poorly were extremely unlikely to catch up and are a group at risk of poorer educational outcomes over the longer term. Recent research from the Millenium Cohort Study (Blanden and Michin, 2010) partially replicated this analysis with similar results; children from higher income households with poorer vocabulary at age 3 improved more quickly than their lower-income peers. The same research, whilst also identifying a gap in attainment at both ages 3 and 5 between children in the lowest and highest income groups, did not demonstrate any significant widening of the ability gap between these groups of children in that specific period, contrary to Feinstein's earlier data, but neither did they show that the gap narrowed.

These, and other studies, demonstrate clearly that the relationship between social background and cognitive development is present at pre-school age (see also Denton, West and Walston, 2003) and even before (McCall 1981). Crucially, long-term analysis of cognitive development and attainment from birth, through pre-school into school and beyond suggests that children's movement between ability groups slows on entering school. Feinstein (2000) found that assessment scores at 60 months were more closely related to educational qualifications at age 26 than were earlier scores. Such evidence has led a number of authors to conclude that patterns of cognitive development and attainment are more difficult to change once children enter school (Heckman and Wax, 2004; see also evidence from CECD and Mustard in Haw, 2010). Other evidence demonstrates the potential long-term benefits of narrowing the early ability gap on, for example, reducing inequalities in final educational attainment or labour market participation (Feinstein, 2000; Heckman et al, 2006; Sinclair, 2007). Combined, these findings highlight the important role that experiences and development during the early years have on later educational achievement and suggest that more should be done to maximise the improvement of children's development before they enter school, including in the immediate pre-school period.

The theme of early intervention has been a prominent feature of much recent UK and Scottish Government policy. In Scotland, the National Performance Framework, which has underpinned and provided focus to all policy development since 2007, has as one of its national outcomes that "children should have the best start in life and are ready to succeed". To achieve this, each of the three policy frameworks - Achieving Our Potential, Equally Well and the Early Years Framework - acknowledge the importance of early intervention and the improvement of children's circumstances in the early years in order to benefit them in later life. The particular economic benefits of early intervention to Scotland's public spending have also recently been explored (Finance Committee of the Scottish Parliament, 2011; Scottish Government, 2010a). The preventative spending enquiry led by the Scottish Parliament's Finance Committee examined how public spending could be focussed more on preventing negative outcomes than dealing with them when they occur. In written evidence to the enquiry, the Scottish Government noted that preventative action was "integral to the approach to government in Scotland and delivering the outcomes set out in the National Performance Framework" (Scottish Government, 2010). Similar policy moves are also evident in the UK Government reflected, for example, through their concurrent commissioning of an independent review of early intervention (Allen, 2011) and the independent review on poverty and life chances (Field, 2010).

Data from the Growing Up in Scotland study ( GUS) offers the potential to present a detailed exploration of changes in children's cognitive ability - more specifically their knowledge of vocabulary and skills in non-verbal reasoning - between the ages of 3 and 5 and to identify the factors associated with different directions and magnitudes of change for different groups of children, adding to the existing evidence referenced above. The existing analysis of GUS data on this topic has focused on cognitive ability at a single time point - age 3 (34 months) and the child's circumstances and experiences prior to that. The same cognitive assessments were more recently repeated at the fifth sweep of fieldwork, when the children were aged 5 (58 months). Using these two sets of data, this research will explore change in cognitive ability between the ages of 3 and 5 and examine, in particular, the extent to which early gaps in ability by children's social background remain, reduce or increase in this period.

A key aim of this report is to identify which circumstances and experiences contribute to the improvement of cognitive ability of children in lower (and higher) SES groups in the pre-school period. The results will allow policy to focus on improving those circumstances and experiences in order to maximise children's cognitive ability ahead of entering school in a period shown, in the longer-term research cited above, to be crucial to children's outcomes in adulthood. The pre-school period presents a unique opportunity for policy to make an impact on children's lives via statutory pre-school education. Evidence from GUS (Bradshaw et al, 2009) and from Scottish Government statistics (Scottish Government, 2010) suggests that over 95% of children eligible for a pre-school place take-up that place. Understanding better the factors which inhibit and which improve children's cognitive ability during this time will permit the provision of services and support to maximise children's ability ahead of school entry. In so doing, outcomes for children in these domains will not only improve throughout their school career but also beyond, in their transitions to further education and employment.

1.2 Adding to the evidence base

This report will go beyond the existing analysis of BCS 1970 and MCS data by investigating which factors, in addition to indicators of social background - such as child health, parenting behaviours and area deprivation - impact on changes in cognitive development between the ages of 3 and 5. The focus of much work in this area has been on differences observed by household income and social class ¹ (Blanden and Machin, 2010; Feinstein, 2003; Waldfogel and Washbrook, 2010). For example, recent analysis of MCS data (Blanden and Machin, 2010) suggested that there was little change in the size of the ability gap between children in lower and higher income households between ages 3 and 5, and further that average scores amongst children in the lowest income groups had not declined during the period considered. This was cautiously offered as a small, but positive improvement for that group. As this report will show, GUS data, whilst detecting only a small amount of change in the income ability gap, suggests that gap narrows during the pre-school period with children in all income groups showing a relative improvement in scores, but particularly those in the lowest income group. This contrasts with change across income groups in relation to problem solving ability, where a slight increase in the ability gap is evident. Whilst household income and social class will be considered initially, the analysis of ability gaps in this report will centre on differences by level of parental education.

In addition, whereas only data on vocabulary acquisition has been considered in the previous analyses, the GUS analysis will also examine changes in problem solving ability (non-verbal reasoning). The analyses in this report suggest that the variations in ability observed by level of parental education are quite different to those associated with income. Our findings suggest that lack of parental qualifications has a continuing detrimental effect on children's vocabulary ability during the pre-school years seeing those children fall further behind their peers ahead of their entry to school.

1.3 Research questions

This report aims to answer a number of distinct research questions:

• Does the gap in cognitive ability between children with different social background characteristics change between ages 3 and 5?
• Which factors help or hinder improvement in cognitive ability between ages 3 and 5?
• Are the factors which influence improvements in cognitive ability during the pre-school period different for children whose parents have lower levels of educational qualifications and those whose parents have higher level qualifications?

Initial analysis will look simply at the difference in cognitive ability at ages 3 and 5 between children with different social backgrounds. Social background characteristics considered will include parental education, annual household equivalised income and socio-economic classification. Comparison of average scores on each of the assessments for children in each of the groups is undertaken to demonstrate broad differences in ability, and to identify any changes in the magnitude of those differences at an overall level.

The next stage of the analysis draws on the existing literature to identify potential factors which may be associated with improving children's cognitive development in the pre-school period ² .

The final analytical stage examines whether the impact of key factors on pre-school cognitive development are stronger or weaker for children with degree educated parents compared with those whose parents have lower or no qualifications or whether there is no difference in effects at all between children in each group.

1.4 Methods

1.4.1 The Growing Up in Scotland study

The analysis in this report uses information from families in the birth cohort that took part in all of the first five sweeps of GUS ( n = 3621) ³ . Some families who initially took part in GUS did not do so for all of the subsequent sweeps. There are a number of reasons why respondents drop out from longitudinal surveys and such attrition is not random. All of the statistics have been weighted by a specially constructed longitudinal weight to adjust for non-response and sample selection. Both weighted and unweighted sample sizes are given in each table. Standard errors have been adjusted to take account of the cluster sampling ⁴ .

At each sweep/year of fieldwork, interviews took place around six weeks before the child's next birthday, therefore in the first year of the study, children were 10 months old, in the second year they were 22 months old and so on. For the purposes of this report, beyond the first interview, the child's age will be referred to in years. It is worth bearing in mind however that a 3-year-old child at sweep 3 for example, is actually 34 months old or just under 3, and a 5-year-old child at sweep 5 is actually 58 months old or just under 5.

1.4.2 Measuring cognitive ability

Cognitive ability was measured in the GUS birth cohort via two assessments: the naming vocabulary and picture similarities subtests of the British Ability Scales Second Edition ( BASII). These two assessments measure, respectively, language development and problem solving skills. Each subtest is part of a cognitive assessment battery designed for children aged between 2 years and 6 months and 17 years and 11 months. The assessments are individually administered. Numerous tests of ability and intelligence exist but the BAS is particularly suitable for administration in a social survey like GUS.

The naming vocabulary assessment measures a child's language development. The test requires the child to name a series of pictures of everyday items and assesses the expressive language ability of children. The picture similarities assessment measures a child's problem solving ability (or non-verbal reasoning). In the assessment children are shown a row of four pictures on a page. They are asked to place a free-standing card with a fifth picture underneath the picture with which the card shares a similar element or concept. There are 36 items in total in the naming vocabulary assessment and 33 items in the picture similarities assessment. However, to reduce burden and to avoid children being upset by the experience of repeatedly failing items within the scale, the number of items administered to each child is dependent on their performance. For example, one of the criteria for terminating the naming vocabulary assessment is if five successive items are answered incorrectly.

Children in the birth cohort have been asked to complete the same two assessments at two different sweeps of data collection: sweep 3, when they were aged 3 years old (34 months) and sweep 5, when they were aged 5 years old (58 months). As such, the assessment scores offer a snapshot of children's ability in expressive vocabulary and problem solving, first a little ahead of their entry to pre-school education, and second around the time they start primary school.

As children age, their expected rate of development and their expected ability level also changes. As such, the assessments alter slightly with a different item range used at age 5 as compared with age 3. Furthermore, ability scores at age 5 tend to be higher across the board than scores at age 3. As a result, the basic, raw 'ability' score generated from the assessment cannot be compared across time as a child's ability will usually improve with age as a matter of course, and the rate of improvement will differ at different ages (being generally faster at younger ages). In order to examine whether a child's ability relative to his or her peers changes over time therefore, the ability score from each age point was standardised into a z-score. Z-scores are derived from the survey data, they count the number of standard deviations ⁵ from the score mean and have a mean of zero. Therefore a child with a z-score of zero at either age 3 or 5 has an average ability across all children in that age group. Those with a z-score greater than zero scored above average and those with a score of less than zero scored below average. By using the standardised scores it is possible to compare ability at age 3 and 5 and to consider whether children who scored above, below or about average at age 3 continued to do so at age 5.

1.5 Technical Appendix

Readers interested in the details of the analyses should consult the Technical Appendix published alongside this report.