Cognitive load at checkout: how information complexity and default nudges shape sustainable delivery choices

As e-commerce continues to expand, last-mile delivery has become a salient yet underexplored source of environmental impact, with delivery choices increasingly delegated to consumers at checkout. A growing literature examines how sustainability-related nudges shape consumer decisions, yet research on last-mile delivery has largely focused on upstream logistical and technological solutions rather than on the downstream checkout decision where delivery modes are selected. Drawing on Cognitive Load Theory, this research investigates how digital choice architecture at checkout influences sustainable delivery choice, focusing on the roles of informational complexity and default preselection in the adoption of Click & Collect. Across one preliminary study and two experiments, we manipulate the complexity of sustainability-related information presented at checkout and the presence of default preselection. Results show that informational nudges exhibit a non-linear effect: Click & Collect adoption increases with moderate informational complexity but declines when information becomes highly detailed, following an inverted U-shaped pattern. Process evidence indicates that increased informational complexity raises perceived cognitive effort, which in turn reduces sustainable delivery choice. Default preselection consistently increases Click & Collect adoption but does not reduce perceived cognitive effort. By conceptualizing checkout as a cognitively constrained decision environment, this research advances understanding of how information design and choice architecture jointly shape sustainable consumer choices in digital contexts.