Making sense of nonsense: the visual salience of units determines sensitivity to magnitude

When are people sensitive to the magnitude of numerical information presented in unfamiliar units, such as a price in a foreign currency or a measurement of an unfamiliar product attribute? We propose that people exhibit deliberational blindness, a failure to consider the meaning of even unfamiliar units. When an unfamiliar unit is not salient, people fail to take their lack of knowledge into account, and their judgments reflect sensitivity to the magnitude of the number. However, subtly manipulating the visual salience of the unit (e.g., enlarging its font size relative to the font size of the number) prompts recognition of the unit's unfamiliarity and reduces magnitude sensitivity. In five experiments, we demonstrated this unit-salience effect, provided evidence for deliberational blindness, and ruled out alternative explanations, such as nonperception and fluency. These findings have implications for decision making involving numerical information expressed in both unfamiliar units and familiar but poorly calibrated units.