BCS70 Sub studies

Twin studies are often used to study the relative importance of nature versus nurture. BCS70 did not have particularly reliable information about zygosity (whether twins are genetically identical), which made it difficult to conduct this type of research with the information collected from BCS70 twins. As such, in 2008, a postal questionnaire was sent to all pairs of twins with a series of questions to allow zygosity to be accurately identified.

The study was undertaken as a part of the project The Relative Importance of Nature, Nurture, and Peer Effects on Adult Outcomes, funded by the Economic and Social Research Council.

The aims and objectives of the project were:

1. to provide a more complete and accurate dataset which identifies the zygosity (whether the twins were identical or not) of the twins in the NCDS and the BCS70
2. to use the data held on the twins in the NCDS and BCS70 to consider the relative importance of nature, nurture, and peer effects in childhood and adult outcomes such as education, employment, and earnings
3. to identify the relative importance of nature, nurture, and peer effects on each adult outcome across the two cohorts and within the two cohorts across time in order to assess whether and how these relative effects change over the life course and the stability or change in these patterns for people born at different times.

This questionnaire was developed based on existing instruments used by other twin studies, and covers self-reported zygosity, physical similarity, and widely used ‘peas-in-a-pod’ questions. A dataset was created from the collected questionnaires, containing three new measures of zygosity.

This sweep was conducted with a sub-sample of the cohort.

The sweep comprised four sections: the main interview, a set of literacy and numeracy assessments and two self-completion questionnaires (‘Your Life Since 1986’ and ‘Your Views’).

The interview covered qualifications, training, current employment, unemployment, reading and writing behaviour, literacy and numeracy self-appraisal, household composition, relationships, children, housing, income and health.

The literacy and numeracy assessments comprised a series of 17 tasks using showcards, to assess reading, writing, comprehension and simple mathematical skills.

The ‘Your Life Since 1986’ questionnaire covered employment and education histories since 1986, and ‘Your Views’ gathered information on attitudes to employment, education, literacy, numeracy, self-efficacy, health and opinion of respondent’s life so far.

The 7-year sample survey was undertaken to try and contact the children who had not been able to be followed up at the full 5-year sweep.

It was successful in locating 4,760 children, many of whom might otherwise have been lost forever from future sweeps.

The 22-Month and 42-Month Surveys Sweeps focused on exploring the impact of foetal nutrition on early development. Those invited to take part in the 22-Month Sweep were 10 per cent of all study members, all twins and triplets, those born after more than 42 weeks of gestation, and those who had particularly low birthweight. Around 2,500 took part. A similar number, though not the same people, took part in the 42-Month Sweep.

The 22 month sweep covered family circumstances, housing situation, parental smoking, use of childcare, illnesses since birth and a series of tests to measure development including a pencil and paper test where the child was asked to draw a series of simple shapes and a language test where the child was asked to show the examiner different body parts (e.g. hair, hand). The medical examination assessed weight, height, recumbent length, head circumference and other health problems.

The 42 month sweep covered family circumstances, housing situation and a further set of assessments measuring development including making structures using cubes, a vocabulary assessment and drawing shapes. The medical examination assessed height, weight and head circumference.