Reducing the Linear Perception of Nonlinearity: Use of a Physical Representation

Research shows that while judging accumulations of quantities over time (e.g., money in a bank account or CO₂ in Earth's atmosphere), people assume that the shape of the accumulation is similar to the shape of the inflow (i.e., people rely on a correlation heuristic). Relying on the correlation heuristic is particularly worrisome for Earth's climate, as judging the CO₂ accumulation according to its emissions (inflow) would underestimate the actual (nonlinear) increase. This misperception undermines the seriousness of climate problem and results in wait-and-see behavior. We report two experiments where the effectiveness of a physical representation is compared with graphical and text representations in reducing people's underestimation of nonlinear accumulation in different contexts and problems. A physical representation presents an accumulation using a picture that works as a metaphor. In the first experiment, participants drew the shape of an accumulation over time relying on physical or graphical representations in one of two contexts: carbon dioxide and marbles. Although the participants underestimated the accumulation in both contexts, underestimations were reduced in the physical representation compared with the graphical representation. In the second experiment, we extended the evaluation of physical representations against both text and graphical representations in two different climate problems (with linearly increasing or decreasing inflow). Again, underestimations of the accumulation were reduced in the physical representation compared with the other two representations, regardless of the nature of the problem. We discuss implications of using the physical representation for improving people's estimates of nonlinear CO₂ accumulation. Copyright © 2011 John Wiley & Sons, Ltd.