Titolo della tesi: Adaptive Foraging in Humans: Behavioural Flexibility under Constraints, Volatility, and Structural Demands
Foraging is a universal adaptive behaviour, fundamental for the survival of most species (Mobbs et al., 2018; Hayden, 2018). At its core, it entails balancing exploration, seeking new opportunities or, in the so-called “patch-leaving problems”, moving to new patches or areas, and exploitation, maximizing the use of currently available resources. This trade-off, central to Optimal Foraging Theory (OFT) (Charnov, 1976), is widely regarded as a hallmark of cognitive flexibility and has been studied extensively in the animal kingdom (Stephens and Krebs, 1986), and is increasingly being applied to humans. Yet important questions remain about how foraging unfolds in complex, uncertain, volatile, or structured environments. This thesis addresses these questions through three studies examining adaptive foraging in humans under different environmental demands.
Studying foraging offers a powerful lens on the principles of flexible, goal-directed behaviour in real-world contexts. Just as a lion must decide whether to pursue a gazelle, humans face comparable foraging-like dilemmas in daily life: selecting a job candidate, deciding whether to invest in a relationship, choosing a restaurant among many alternatives, browsing e-commerce platforms for the best deal, or even deciding which movie to watch on a streaming service. In this spirit, the studies presented in this thesis are framed through the everyday-life metaphor of a supermarket trip (Schlender et al., 2024), one of the most familiar human foraging situations, where aisles can be conceived as analogous to resource patches.
Imagine a shopper entering a supermarket with limited time and uncertain knowledge of which aisles contain the most profitable items. In this kind of scenario, the shopper must decide whether to continue collecting items in the current aisle or explore another, gradually learning which areas are most rewarding and how to best allocate their time. Analogously, in our first study participants navigated a four-area environment to collect coins from treasure boxes, adapting to resource distributions and time constraints. Their strategies improved with experience, approaching, though not fully reaching, the performance of an optimal reward-maximizing agent.
Now, consider a more dynamic supermarket, with the location of the most profitable items shifting according to a hidden alternating rule (e.g., fruit and vegetables on even weeks, meat and fish on odd weeks). This scenario introduces environmental volatility, where contingencies change over time and require continual monitoring and adaptation. Similarly, in our second experiment, the location of rich areas varied according to a hidden rule. Most participants detected this volatility and flexibly adjusted their strategies, although individual differences
emerged: participants with higher autistic traits, measured by the Autism Spectrum Quotient (AQ) (Baron-Cohen et al., 2001), exhibited slower adjustments following rule changes.
Finally, imagine two supermarkets with contrasting layouts: one structured, with items organized by category (e.g., fruit and vegetables in one aisle, meat and fish in another), and another unstructured, with items scattered randomly. In the structured store, shoppers may adopt hierarchical plans (e.g., collect vegetables first, then meat), whereas in the unstructured store, they may simply follow the shortest path to nearby items. Likewise, in our third study participants collected coloured spheres in a grid-like virtual environment, adapting their strategies to the environmental structure: hierarchical approaches predominated in structured layouts, while shortest-path strategies were favoured in unstructured ones.
Taken together, these three studies demonstrate that human foraging is highly flexible: people adapt their strategies to resource distribution, time limits, and environmental volatility, and tailor their planning to the structural organization of the environment. At the same time, behaviour does not always align with optimal models, highlighting the role of cognitive constraints and individual differences. By showing how ecological factors and subtle structural cues shape foraging behaviour, this thesis advances our understanding of how humans navigate complex, uncertain, and dynamic environments.