When A+B < A: Cognitive Bias in Experts’ Judgment of Environmental Impact

Abstract

When ‘environmentally friendly’ items are added to a set of conventional items, people report that the total set will have a lower environmental impact even though the actual impact increases. One hypothesis is that this “negative footprint illusion” arises because people, who are susceptible to the illusion, lack necessary knowledge of the item’s actual environmental impact, perhaps coupled with a lack of mathematical skills. The study reported here addressed this hypothesis by recruiting participants (‘experts’) from a master’s program in energy systems, who thus have bachelor degrees in energy-related fields including academic training in mathematics. They were asked to estimate the number of trees needed to compensate for the environmental burden of two sets of buildings: one set of 150 buildings with conventional energy ratings and one set including the same 150 buildings but also 50 ‘green’ (energy-efficient) buildings. The experts reported that less trees were needed to compensate for the set with 150 conventional and 50 ‘green’ buildings compared to the set with only the 150 conventional buildings. This negative footprint illusion was as large in magnitude for the experts as it was for a group of novices without academic training in energy-related fields. We conclude that people are not immune to the negative footprint illusion even when they have the knowledge necessary to make accurate judgments.

Assuming the Best: Individual Differences in Compensatory “Green” Beliefs Predict Susceptibility to the Negative Footprint Illusion

“…On the most basic level, it could be influenced by poor mathematical skills in participants. However, as the NFI was also demonstrated in a study which had only masters-level engineering students for participants [20], this provides some evidence that it might not be related to mathematical ability. It has been posited that an averaging bias could underlie the NFI [10,19], namely that the environmental impact of a set of items which include a green product is calculated as the average rather than the sum of those products (when the calculation would ordinarily have been additive).…”

Pre-Service Science Teachers’ Perceptual Biases Regarding Sustainable Food Consumption: Negative Footprint Illusion

“…Accordingly, the present research focuses on revealing consumers' perspectives about the environmental effects of foods by drawing attention to potential perceptual biases. Considering previous studies, several studies examined the negative footprint illusion of general products such as buildings (e.g., Holmgren et al, 2018aHolmgren et al, , 2018b and mental models (e.g., Kim & Schuldt, 2018;Holmgren, Kabanshi, Langeborg, Barthel, Colding, Eriksson, & Sörqvist, 2019), while only a few studies focused on perceptual biases related to food products' environmental impact (e.g., Gorissen & Weijters, 2016;Kusch, & Fiebelkorn, 2019). Accordingly, due to the insufficient number of studies, the current study was carried out to reveal the importance of fully understanding the negative footprint illusion.…”

Are We Overestimating the Benefits of Emission Reduction Measures?

“…One would think that people who are susceptible to the averaging bias lack the necessary knowledge or skills for environmental evaluation or impact assessments, consequently failing to understand the impact of their own behavior. A recent study [34] addressed this hypothesis by recruiting final year graduate students in energy systems who had knowledge of building energy systems and environmental assessments as these are extensively covered in their study program. The students were presented with two sets of buildings, each with an image typically used to present details of energy efficiency of buildings.…”

“…processing chain is the average of the items in the combined set (environmentally friendly and harmful objects) but not the sum of the items. The problem that people face here is categorization, similar to the problem concerning the environmental impact of objects in Holmgren et al [26,34]. When assessing the environmental impact of a set of environmentally friendly actions or behavior, the proposed framework suggests that people tend to overlook the quantitative details even when such is provided, but rather categorize attributes qualitatively and thus end up with an average of these objects or actions rather than the sum.…”