The pain of paying — amplified by delivery fees
In 2007, Brian Knutson at Stanford, Scott Rick at Carnegie Mellon, and Drazen Prelec at MIT put subjects in an fMRI machine and showed them products at various prices. Their finding, published in Neuron: excessive prices activated the insula — a brain region associated with physical pain — and this activation predicted whether subjects would decline a purchase seconds later.
37%More spending when costs are split equally versus individually, per Gneezy, Haruvy & Yafe’s 2004 field experiment at restaurants in Tucson, Arizona.
Delivery fees exploit this neural mechanism in a specific way. Prelec and Loewenstein’s earlier research on the “pain of paying,” published in Marketing Science (1998), showed that bundled costs create less payment pain than itemized ones. When Uber Eats shows a single total rather than breaking down each fee component, the aggregate number triggers less insula activation than seeing each fee separately. This is why the total feels “okay” at checkout but seems outrageous when you later itemize the receipt for splitting.
That shift — from bundled acceptance to itemized shock — is exactly when the “I’ll Venmo you later” problem kicks in. Hermann Ebbinghaus demonstrated in 1885 that memory decays exponentially: 70% of newly learned information is lost within 24 hours. Applied to group delivery orders, this means the details of who ordered what fade rapidly. By the next morning, the precise breakdown is fuzzy enough that most people round down what they owe.
Sources: Knutson, Rick, Wimmer, Prelec & Loewenstein, “Neural Predictors of Purchases,” Neuron (2007); Prelec & Loewenstein, “The Red and the Black,” Marketing Science (1998); Ebbinghaus, Memory: A Contribution to Experimental Psychology (1885)