Decision prioritization and causal reasoning in decision hierarchies.

Ariel Zylberberg

doi:10.1371/journal.pcbi.1009688

Ariel Zylberberg

Open Access

https://doi.org/10.1371/journal.pcbi.1009688

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Abstract

From cooking a meal to finding a route to a destination, many real life decisions can be decomposed into a hierarchy of sub-decisions. In a hierarchy, choosing which decision to think about requires planning over a potentially vast space of possible decision sequences. To gain insight into how people decide what to decide on, we studied a novel task that combines perceptual decision making, active sensing and hierarchical and counterfactual reasoning. Human participants had to find a target hidden at the lowest level of a decision tree. They could solicit information from the different nodes of the decision tree to gather noisy evidence about the target’s location. Feedback was given only after errors at the leaf nodes and provided ambiguous evidence about the cause of the error. Despite the complexity of task (with 107 latent states) participants were able to plan efficiently in the task. A computational model of this process identified a small number of heuristics of low computational complexity that accounted for human behavior. These heuristics include making categorical decisions at the branching points of the decision tree rather than carrying forward entire probability distributions, discarding sensory evidence deemed unreliable to make a choice, and using choice confidence to infer the cause of the error after an initial plan failed. Plans based on probabilistic inference or myopic sampling norms could not capture participants’ behavior. Our results show that it is possible to identify hallmarks of heuristic planning with sensing in human behavior and that the use of tasks of intermediate complexity helps identify the rules underlying human ability to reason over decision hierarchies.

Highlights

Many real-life decisions are organized hierarchically in the sense that they are composed of parts that themselves can be considered decisions
They did so by adopting a planning strategy based on a small set of heuristics. These include discarding information deemed unreliable to make a decision; a bias towards resolving uncertainty locally, collapsing probabilistic information into a categorical decision rather than carrying forward entire probability distributions; and the use of confidence to disambiguate negative feedback after an error. These results extends the framework of perceptual decision making to more complex decisions that comprise a hierarchy of sub-decisions
Each internal node of the decision tree was assigned a direction of motion, which could be rightward or leftward

Summary

Introduction

Many real-life decisions are organized hierarchically in the sense that they are composed of parts that themselves can be considered decisions. Consider an engineer who must diagnose the cause of failure at an industrial plant. The engineer might break down this complex decision into a sequence of simpler ones These decisions are resolved by specific information-seeking actions (i.e., tests), where the outcome of each test influences the subsequent ones. The engineer may conclude that the failure was due to wear of the pump bearings and decide to replace them. If changing the pump’s bearings does not restore the plant’s function, the engineer must determine the cause of her flawed reasoning and decide what action to take (e.g., conduct a new test, repeat an unreliable one, or replace a different component)

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