Fatigue biases the decoy effect in males but not females: FATIGUE BIASES THE DECOY EFFECT

: Individuals often need to make critical decisions even when they are in a fatigued state. Mental fatigue may lead to increased susceptibility to distraction and poor information processing but it is unclear exactly how fatigue shapes individuals' decision-making. We studied how mental fatigue influences sensitivity to contextual information, indexed as decoy bias. Mental fatigue was induced using a multi-source interference task, and decoy bias was assessed using a gambling task, in 124 young adults. Results showed that mental fatigue increased decoy bias through enhanced perceptual salience of contextual cues, but only in males. The findings provide insight into a gender-specific relationship between fatigue and poor judgments. This study extends the current literature on links between fatigue and poor decision-making by documenting a possible mechanism of the association. The results may have practical implications for designing optimal working hours and safeguarding people from suboptimal decisions.