Attitudes Over Time: The Psychology of Panel Conditioning

INTRODUCTION Panel studies are of crucial importance to our understanding of the complex, interacting, and dynamic nature of causal processes in the social world. A limitation to valid inference from panel studies, however, derives from the reflexive nature of humans as research subjects; the very act of observation can serve to transform the behaviour of those being observed (Kalton and Citro 2000). In panel studies this source of error falls under the general heading of ‘panel conditioning’ or ‘time in sample’ bias and relates to the fact that responses to questions in later rounds of the panel may be influenced by those given in earlier waves. The majority of empirical investigations of panel conditioning effects have focused on estimating biases in marginal totals of behavioural frequency, such as electoral turnout (Clausen 1969), consumer spending (Pennell and Lepkowski 1992) and alcohol and drug use (Johnson, Gerstein, and Rasinski 1998). However, less attention has been paid to how repeated interviewing might influence attitudinal responses. The cognitive processes underlying responses to attitude questions are, however, quite different in nature to those involved in reporting the frequency of behaviours (Schuman and Presser 1981). Additionally, much of the existing body of research in the area of panel conditioning has been largely atheoretical, with a primary focus on estimating the direction and magnitude of possible biases, as opposed to an elucidation of the causal mechanisms underlying conditioning effects (Holt 1989). In this paper, our focus is on panel conditioning with respect to attitude questions. Our methodological approach is different from the majority of previous studies in this area in that we do not attempt to estimate biases in marginal and associational distributions through comparison with a fresh cross-sectional sample. Rather, our approach is based on testing hypotheses on a single data set, derived from an explicit theoretical model of the psychological mechanism underlying conditioning effects in repeated measures of the attitude. We refer to this as the cognitive stimulus (CS) hypothesis. Specifically, we use a range of empirical indicators to evaluate the theory that repeatedly administering attitude questions serves to stimulate respondents to reflect and deliberate more closely on the issues to which the questions pertain. This, in turn, results in stronger and more internally consistent attitudes in the later waves of a panel. The paper proceeds in the following manner. First, we review the existing literature on panel conditioning effects. Next, we set out in more detail the rationale underlying the CS hypothesis. We then use data from the first ten waves of the British Household Panel Study (BHPS) to test four inter-related hypotheses expressed as empirical expectations of the CS