Lay summary
We aim to investigate the relationship between children's perceptions of portion sizes and marketing of unhealthy food and drink products. We will use different visual estimation and comparison tasks, in a series of child-friendly experiments. We hypothesise that when compared to plain packaging, marketing will distort children’s visual perceptions of portion sizes, which has potential to negatively influence their dietary preferences and their ability to self-regulate appropriate nutritional intake. The impact of this research will be to demonstrate the influences of unhealthy advertising on children’s real-world cognitive judgments, informing future research and practice in public health promotion and health delivery.