Anthropomorphic or non-anthropomorphic? Effects of biological sex in observation of actions in a digital human model and a gantry robot model

Abstract

Robots are ever more relevant for everyday life, such as healthcare or rehabilitation, as well as for modern industrial environment. One important issue in this context is the way we perceive robots and their actions. From our previous study, evidence exists that sex can affect the way people perceive certain robot's actions. In our fMRI study, we analyzed brain activations of female and male participants, while they observed anthropomorphic and robotic movements performed by a human or a robot model. While lying in the scanner, participants rated the perceived level of anthropomorphic and robotic likeness of movements in the two models. The observation of the human model and the anthropomorphic movements similarly activated the biological motion coding areas in posterior temporal and parietal areas. The observation of the robot model activated predominantly areas of the ventral stream, whereas the observation of robotic movements activated predominantly the primary and higher order motor areas. To note, this later activation originated mainly from female participants, whereas male participants activated, in both robot model and robotic movements contrasts, areas in the posterior parietal cortex. Accordingly, the general contrast of sex suggests that men tend to use the ventro-dorsal stream most plausibly to rely on available previous knowledge to analyze the movements, whereas female participants use the dorso-dorsal and the ventral streams to analyze online the differences between the movement types and between the different models. The study is a first step toward the understanding of sex differences in the processing of anthropomorphic and robotic movements.

Keywords: action observation system; anthropomorphism; digital human model; gantry robot model; gender effect; human-robot interaction; motion perception.

Figure 1

Visual representation of the factorial design: the depicted trajectories (projections on the X,Y plane) belong to a digital human model and to a gantry robot model performing anthropomorphic and robotic movements. The unit is millimeter (mm) (Abel et al., 2020).

Figure 2

Study design of a fMRT trial.

Figure 3

Group comparison between (A) female and (B) male participants [p < 0.05 (FWE), k = 0]. R, right hemisphere; L, left hemisphere.

Figure 4

Main effect for each condition: (A) robot model vs. human model, (B) human model vs. robot model, (C) anthropomorphic movement vs. robotic movement, (D) robotic movement vs. anthropomorphic movement in the right (R) and left (L) hemisphere [p < 0.05 (FWE), k = 0].

Figure 5

Group comparison between female and male participants in each condition. Significant activations for female participants in the contrast (A) robot model vs. human model and (B) robotic movement vs. anthropomorphic movement. Significant activations for male participants in the contrast (C) robot model vs. human model and (D) robotic movement vs. anthropomorphic movement. R, right hemisphere; L, left hemisphere (for visualization purposes, a threshold uncorrected p < 0.001, k = 10, was applied).