The portion size effect on food intake. An anchoring and adjustment process?

Area of Science:

• Behavioral Economics
• Cognitive Psychology
• Nutritional Science

Background:

• The portion size effect, where individuals overeat larger food portions, is a well-documented phenomenon.
• The underlying psychological mechanisms driving the portion size effect remain incompletely understood.
• Existing research highlights the impact of external cues on food intake, but precise cognitive processes are debated.

Purpose of the Study:

• To investigate the portion size effect using the anchoring and adjustment heuristic as a theoretical framework.
• To determine if portion size serves as a cognitive anchor influencing food consumption estimates.
• To examine the moderating role of discounting information on the anchoring effect in hypothetical eating scenarios.

Main Methods:

• Application of the classical anchoring and adjustment paradigm to hypothetical eating situations.
• Participants estimated food consumption after imagining being served either small (low anchor) or large (high anchor) portions.
• Comparison of consumption estimates between anchoring conditions and a no-anchor control, with and without a discounting manipulation.

Main Results:

• Imagining larger portions led to significantly higher consumption estimates compared to the no-anchor condition.
• Imagining smaller portions led to significantly lower consumption estimates compared to the no-anchor condition.
• A discounting instruction, stating the portion was random, did not diminish the anchoring effect on consumption estimates.

Conclusions:

• The anchoring and adjustment heuristic provides a robust framework for understanding the portion size effect in food consumption.
• Portion size acts as a potent cognitive anchor, influencing estimated intake even when participants are informed the size is arbitrary.
• Findings suggest that interventions aimed at mitigating overeating should consider cognitive biases related to portion size perception.