# Grocery Shopping Under Simplified Marginal Value Theorem Predictions

## TL;DR

This study shows that the Marginal Value Theorem can model human shopping behavior in supermarkets, similar to how animals forage for food.

## Contribution

The study demonstrates the applicability of optimal foraging theory to human grocery shopping using verbal reports.

## Key findings

- The exponential model predicted the relationship between shopping time and gains in Euros.
- Results supported the MVT-based model despite uncertainty in estimating the upper asymptote.
- Verbal reports proved useful for modeling human shopping behavior under MVT.

## Abstract

This study examined whether supermarkets can be considered patches in the marginal value theorem (MVT) sense despite their particular features and whether they are models of human food foraging in resource-dense conditions. On the basis of the MVT, the quantitative relationship between gains in the Euro and patch residence time was modeled as an exponential growth function toward an upper asymptote, allowing the choice of an optimal strategy under diminishing returns. N = 61 participants were interviewed about their current shopping trip and contextual variables at a German supermarket and provided data to estimate relevant model parameters. A nonlinear model of the patch residence time and resulting gain based on an exponential function was fitted via nonlinear orthogonal distance regression. The results generally revealed the relationships predicted by the model, with some uncertainty regarding the estimation of the upper asymptote due to a lack of data from participants with long residence times. Despite this limitation, the data support the applicability of the MVT-based model. The results show that approaches from optimal foraging theory, such as the MVT, can be used successfully to model human shopping behavior even when participants’ verbal reports are used.