Latent interaction effects in the theory of planned behaviour applied to quitting smoking

Objectives. This study applies three latent interaction models in the theory of planned behaviour (TPB; Ajzen, 1988, Attitudes, personality, and behavior. Homewood, IL: Dorsey Press; Ajzen, 1991, Organ. Behav. Hum. Decis. Process., 50, 179) to quitting smoking: (1) attitude x perceived behavioural control on intention; (2) subjective norms (SN) x attitude on intention; and (3) perceived behavioural control x intention on quitting behaviour. Methods. The data derive from a longitudinal Internet survey of 939 smokers aged 15-74 over a period of 4 months. Latent interaction effects were estimated using the double-mean-centred unconstrained approach (Lin et al., 2010, Struct. Equ. Modeling, 17, 374) in LISREL. Results. Attitude x SN and attitude x perceived behavioural control both showed a significant interaction effect on intention. No significant interaction effect was found for perceived behavioural control x intention on quitting. Conclusions. The latent interaction approach is a useful method for investigating specific conditions between TPB components in the context of quitting behaviour. Theoretical and practical implications of the results are discussed.