Children have only been used as survey respondents since about 1990 (Bell, 2007); before this, it was considered that their responses to questions would not be reliable or valid. More recently, cognitive interviewing has been used to determine what kinds of questions and their phraseology, and with what levels of complexity produce the best possible data quality in surveys of children. Geiselman and Padilla (1988) studied 7- to 12-year-old children and found that cognitive interviews elicited 21 per cent more information than standard interviewing methods (cited in Jaśkiewicz-Obydzińska and Wach, 1995).

While piloting is common in the methodological development of survey questionnaires, few studies include a cognitive interview component. This chapter explains its application in the EU Kids Online study and provides a content analysis of some of the cognitive interview data. Additional analysis of the responses from the final version of the survey illustrates that interviewing children on sensitive subjects is problematic.

Cognitive development

Although Piaget's (1929) work has been criticised on various grounds, its contribution to a general understanding of children's cognitive development continues to be acknowledged. For example, 7- to 11-year-olds are described as being in the ‘concrete operations’ phase, in which many experience difficulty with logic (for example, negations), take literal meanings from what they read, and deal better with the concrete than the abstract (Flavell et al, 1993). Applying Piaget’s theory to administering surveys, children in this age bracket may find it difficult to understand vague quantifiers, for instance, in questions asking for information about the frequency of their behaviours: they require clear definitions. Partially labelled options should be avoided because children need to interpret and translate options without hints (Borgers and Hox, 2000). Riley (2004, p 374) found that 6- to 11-yearolds found it difficult to recall events that occurred several months earlier, and that short recall periods were subject to a ‘telescoping bias, in which highly salient events and trauma are reported as occurring during the recall period, even when they may have happened much further back in time’.

Piaget (1929) labelled the next development stage ‘formal thought’; in this stage children aged 11-15 are able to use formal thinking and manage negations and logic (Borgers et al, 2003).