The-Body Ebbinghaus Illusion: Does Context Matter in Body Size Categorisation?

Abstract

Aims and Objectives: 1) To investigate the impact of context on body size categorisations using the Ebbinghaus Illusion, 2) Increase understanding of disparities in body size categorisation across race and gender. Background: Studies on body weight perception (BWP) have primarily presented single-body stimuli, limited research has been conducted with groups of bodies. Here, we have adopted the Body-Ebbinghaus Illusion to test the impact of context. Methodology: 164 participants completed an online body weight categorisation task, consisting of 160 stimuli: a 2 (Context: Underweight/Obese) x 2 (Gender: Male/Female) x 2 (Race: Black/White) x 4 (BMI: Underweight to Obese) design. Participants were tasked to judge the BMI category of the central target bodies. Results: Not only that participants’ performance (percent accuracy) was affected by Context, intriguingly, along with Context, their judgements were modulated by Race, Gender, or BMI. Overall, they were more accurate when target bodies were surrounded by Underweight bodies. Specifically, with Underweight surroundings, better performance was observed for Black stimuli, and Male bodies. On the Contrary with Obese surroundings, performance was better for White stimuli than Black, and Female bodies than Male. Context also has a significant impact on BMI, performance was higher for leaner bodies with Obese surrounding, but the reverse was true for heavier weights. Our findings revealed that visual judgement of body weight could be modulated by the surrounding, and it is malleable depending on the gender and race of the stimuli. Limitations: The current design may not be able to detect individual’s subjective weight boundaries for the stimuli. Research implications: This could potentially aid the development of intervention programmes in clinical settings. Originality: Previous studies have presented a limited range of stimuli and have tested judgment using single bodies, here, we have highlighted the importance of context/group and used a more diverse range of stimuli.