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. 2015 Sep 21;10(9):e0138642.
doi: 10.1371/journal.pone.0138642. eCollection 2015.

A Bayesian Model of the Uncanny Valley Effect for Explaining the Effects of Therapeutic Robots in Autism Spectrum Disorder

Yuki Ueyama  1
Affiliations

A Bayesian Model of the Uncanny Valley Effect for Explaining the Effects of Therapeutic Robots in Autism Spectrum Disorder

Yuki Ueyama. PLoS One. .

Abstract

One of the core features of autism spectrum disorder (ASD) is impaired reciprocal social interaction, especially in processing emotional information. Social robots are used to encourage children with ASD to take the initiative and to interact with the robotic tools to stimulate emotional responses. However, the existing evidence is limited by poor trial designs. The purpose of this study was to provide computational evidence in support of robot-assisted therapy for children with ASD. We thus propose an emotional model of ASD that adapts a Bayesian model of the uncanny valley effect, which holds that a human-looking robot can provoke repulsion and sensations of eeriness. Based on the unique emotional responses of children with ASD to the robots, we postulate that ASD induces a unique emotional response curve, more like a cliff than a valley. Thus, we performed numerical simulations of robot-assisted therapy to evaluate its effects. The results showed that, although a stimulus fell into the uncanny valley in the typical condition, it was effective at avoiding the uncanny cliff in the ASD condition. Consequently, individuals with ASD may find it more comfortable, and may modify their emotional response, if the robots look like deformed humans, even if they appear "creepy" to typical individuals. Therefore, we suggest that our model explains the effects of robot-assisted therapy in children with ASD and that human-looking robots may have potential advantages for improving social interactions in ASD.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. The uncanny valley hypothesis and the model’s prediction.
The solid blue line indicates the uncanny valley effect. The red dashed line shows the model’s prediction for children with ASD.
Fig 2
Fig 2. Probability of the occurrence of a different stimulus given a broad human category (S 1), and a narrow human category (S 2).
The left- and right-hand panels show the probability densities for S 1 and S 2, respectively.
Fig 3
Fig 3. Probability densities of perceptual categories.
The typical and ASD conditions are defined by μ c2, where the mean of the human category is: typical, μ c2 = 1; ASD, μ c2 = 1.25.
Fig 4
Fig 4. Predictions of the uncanny valley effects according to Moore’s model.
(A) Emotional response plotted as a function of the stimulus and the mean of the human category. The left- and right-hand panels show the three-dimensional representation, and the color image of a plain face, respectively. (B) The uncanny valley curves for the typical and ASD conditions (typical, μ c2 = 1; ASD, μ c2 = 1.25).
Fig 5
Fig 5. Effects of robot-assisted therapy on the variance of the human category.
(A–B) Learned variance of the human category. The left panel is plotted as a function of the trial number and the presented stimulus. The right panel represents the learning curves for some of the presented stimuli: (A) in the typical condition; and (B) in the ASD condition. (C) The terminal values of the learned variance after 500 trials with respect to the presented stimulus.
Fig 6
Fig 6. Effects of robot-assisted therapy on emotional response.
(A) Emotional response in the typical condition plotted as a function of the stimulus and presented stimulus. The left and right panels correspond to the three-dimensional representation, and a color image of a plain face, respectively. (B) Example of the uncanny valley curve changes in the typical condition for 0.4 of the presented stimulus at 0, 50, 150, and 500 trials. (C) Emotional response in the ASD condition plotted as a function of the stimulus and presented stimulus. The left and right panels correspond to the three-dimensional representation, and a color image of a plain face, respectively. (D) Example of the uncanny curve changes in the ASD condition for 0.7 of the presented stimulus at 0, 10, 50, and 500 trials.
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Publication types

Grants and funding

This work was supported by Japan Society for the Promotion Science (JSPS) Grants-in-Aid for Scientific Research (KAKENHI) Grant number 26702023, URL: https://www.jsps.go.jp/english/index.html. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.