http://www.pnas.org/content/early/2014/06/11/1407756111.abstract

Context effects produced by question orders reveal quantum nature of human judgments

Zheng Wanga, Tyler Sollowaya, Richard M. Shiffrinb, and Jerome R. Busemeyerb

Significance

In recent years, quantum probability theory has been used to explain a range of seemingly irrational human decision-making behaviors. The quantum models generally outperform traditional models in fitting human data, but both modeling approaches require optimizing parameter values. However, quantum theory makes a universal, nonparametric prediction for differing outcomes when two successive questions (e.g., attitude judgments) are asked in different orders. Quite remarkably, this prediction was strongly upheld in 70 national surveys carried out over the last decade (and in two laboratory experiments) and is not one derivable by any known cognitive constraints. The findings lend strong support to the idea that human decision making may be based on quantum probability.

Abstract

The hypothesis that human reasoning obeys the laws of quantum rather than classical probability has been used in recent years to explain a variety of seemingly “irrational” judgment and decision-making findings. This article provides independent evidence for this hypothesis based on an a priori prediction, called the quantum question (QQ) equality, concerning the effect of asking attitude questions successively in different orders. We empirically evaluated the predicted QQ equality using 70 national representative surveys and two laboratory experiments that manipulated question orders. Each national study contained 651–3,006 participants. The results provided strong support for the predicted QQ equality. These findings suggest that quantum probability theory, initially invented to explain noncommutativity of measurements in physics, provides a simple account for a surprising regularity regarding measurement order effects in social and behavioral science.

For example, one of the surveys used in the study was a Gallup poll that asked Americans whether Bill Clinton was honest and trustworthy and whether Al Gore was honest and trustworthy.

The survey changed the order in which these questions were asked and, as expected, there were question-order effects found. When respondents were asked about Clinton first, 49% said that both Clinton and Gore were trustworthy. But when respondents were asked about Gore first, 56% said that both were trustworthy.

The pattern that quantum theory predicted was that the number of people who switch from “yes-yes” to “no-no” when the question order is reversed must be balanced by the number of people who switch in the opposite direction.

Indeed, the number of people who said “no-no” — that both Clinton and Gore were not trustworthy — went from 28 percent when the Clinton question was asked first to 21 percent when Gore was first. That seven percent decline essentially cancels out the 7 percent increase in the number of people who said “yes-yes” when the question order was reversed.