Courts and scholars need to be judicious in translating the lessons of consumer neuroscience into new trademark doctrine. The chapter begins by cautioning against the motivated use of science in the courtroom, using the introduction of trademark survey evidence from trained psychologists in the early 1900s as a cautionary tale. Psychologists recognize two models of consumer reasoning: an automatic, emotional model and a deliberative, cognitive model. Neuroscience offers a window into both processes, but courts should be wary of admitting evidence purporting to measure non-deliberative changes in mark meaning. Trademark law has historically limited its remit to the informational components of advertising, in part because changes in a brand’s emotional meaning have been difficult to calculate. Neuroscientific evidence of these changes may now be available, but using them to decide trademark cases could lead to anti-competitive outcomes.