Quantum Zeno effect in decision-making: time delay and no information about previous responses reduce coherence

The quantum cognition approach employs the mathematics of quantum theory to develop models of cognition and decision making. This theory predicts the quantum Zeno effect: when the state of a system is observed continuously, the evolution of state slows down because the quantum state is less likely to change if measures are taken within brief intervals. In the quantum cognition framework, the state vector represents the current cognitive state. When a judgement is made the vector collapses onto the corresponding axis. Over time, the vector oscillates moving away from the axis. By asking the same question multiple times, it is observed that the shorter the interval, the nearer the state vector will be to the axis. This implies a higher probability of giving the same response, resulting in a high coherence of judgement. We tested this prediction with two scenarios describing a hypothetical person and asking for a judgement about him/her. We gave two clues about the characteristic of this individual at once for three times. A total of 3241 participants completed the task, online and in person. We manipulated the time interval between each judgment (immediate vs 30 minutes), the availability of the previous responses given by each participant and the social desirability of showing coherence. In both scenarios, we observed an interaction effect between the time interval and the availability of information about previous responses. The coherence was reduced in the case of 30 minutes interval only if information was not available compared to the other conditions. Results are discussed in the light of the comparison between the quantum cognition framework and the classical approach as well as the cognitive processing underlying the coherence of judgements.