Getting a tool gives wings even in schizophrenia: underestimation of tool-related effort in a motor imagery task

Amandine Décombe,François Osiurak,Vincent Murday,Stéphane Raffard,Delphine Capdevielle,Lionel Brunel

doi:10.1038/s41537-021-00175-y

Abstract

Humans frequently use tools to reduce action-related efforts. Interestingly, several studies have demonstrated that individuals had tool-related biases in terms of perceived effort reduction during motor imagery tasks, despite the lack of evidence of real benefits. Reduced effort allocation has been repeatedly found in schizophrenia, but it remains unknown how schizophrenia patients perceive tool-related benefits regarding effort. Twenty-four schizophrenia patients and twenty-four nonclinical participants were instructed to move the same quantities of objects with their hands or with a tool in both real and imagined situations. Imagined and real movement durations were recorded. Similarly to nonclinical participants, patients overestimated tool-related benefits and underestimated tool-related effort in terms of time when they mentally simulated a task requiring the use of a tool. No association between movement durations and psychotic symptoms was found. Our results open new perspectives on the issue of effort in schizophrenia.

Highlights

To achieve a goal, humans tend to adopt strategies to minimize the effort associated with a given action
Tool use is far from being unique to humans[5], humans may be unique in their way of using tools or, more in how they perceive the efforts related to tool use
It has been shown that people overestimate the benefits provided by tool use in terms of cost-benefits, which leads individuals to use a tool even though it objectively provides less time-based benefits than using one’s own hands

Summary

Introduction

Humans tend to adopt strategies to minimize the effort associated with a given action. Contrary to animals[4], humans may be biased in the way they perceive tool-related efforts, in overestimating toolrelated benefits in terms of effort reduction[3]. Results revealed that participants showed a time-related bias in the imagined situation; the participants imagined spending less time using a tool than using their hands, compared to the actions they performed. This was true for trials where tool use did not provide time benefits, as if participants anticipated that they would need less effort by using a tool, resulting in an effort bias toward the tool. Tool use or imagining using a tool have been repeatedly associated with an effortrelated bias toward the tool, even in situations in which the use of a tool does not provide clear and real benefits

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