When Half is At Least 50%: Effect of “Framing” and Probability Level on Frequency Estimates

Abstract

Expert judgment often involves estimating magnitudes, such as the frequency of deaths due to a pandemic. Two experiments (Ns = 902 and 431, respectively) were conducted to examine the effect of outcome framing (half of a threatened group expected to survive vs. die), probability level (low vs. high), and probability format (verbal, numeric range, or combined) on the estimated frequency of survivals/deaths. Both experiments found an interactive effect of frame and probability level that supported the hypothesis that forecasted outcomes received by participants were implicitly quantified as lower bounds (i.e., half interpreted as “at least half”). Responding in a manner consistent with a lower-bound “at least” interpretation was not related to numeracy, verbal reasoning ability, or actively open-minded thinking, although each of these individual difference measures was inversely related to violations of coherence. This suggests that implicit lower bounding is not a cognitive error but rather an aspect of linguistic inference. Methodological and theoretical implications for research on framing effects is discussed.