Do People Pick Up Variables that Reflect Object Height Relative to Actor Height When Perceiving Others’ Maximum Vertical One Degree-of-Freedom Reach Heights and How Might that Inform the Design of Assistive Robots?

Jones et al. (2023) suggest people perceiving others’ maximum vertical one degree-of-freedom reach heights pick up variables that reflect object height relative to actors’ 1) top of head heights when actors’ upper bodies are visible, or 2) leg lengths when only actors’ lower bodies are visible. Leg length is highly correlated with overall height. Accordingly, Jones et al. argued people pick up variables that reflect object height relative to actor height. The current dissertation evaluated Jones et al.’s explanation. In two experiments, participants viewed point-light displays depicting an actor and object. In Experiment 1, actors were depicted with short or tall necks and markers on their full or upper bodies. In Experiment 2, actors were depicted with short or tall legs and markers on their full or lower bodies. Participants judged the actors’ maximum vertical one degree-of-freedom reach heights. In Experiment 1, judgments for the short-necked actors were lower than judgments for the tall-necked actors. In Experiment 2, judgments for the short-legged actors were lower than judgments for the tall-legged actors in the Lower Body condition, but not in the Full Body condition. Follow-up simulations also suggest simulated judgments based on actor height can highly correspond with actors’ maximum vertical one degree-of-freedom reach heights if they are well calibrated and do so nearly as well as simulated judgments based on shoulder height and arm length. These results support Jones et al.’s explanation, enhance our understanding about how people perceive others’ affordances, and inform the design of assistive robots.

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