||Peripheral bodily states affect information processing of action words
Evidence is increasing that brain areas that are responsible for action planning and execution are activated during the information processing of action-related verbs (e.g., pick or kick). To obtain further evidence, we conducted six experiments to see whether constraining arm posture, which could disturb motor planning and imagery for that arm, would lead to the delayed judgment of verbs referring to arm actions. In all experiments, native Japanese speaker participants performed two tasks. In compatibility judgment task, participants judged as quickly as possible whether the presented object and the verb would be compatible (e.g., ball—throw) or not (e.g., ball pour). Constrained arm posture was introduced to the task by asking participants to keep both hands behind their backs. Two types of verbs were used: manual action verbs (MA verbs,i.e., verbs referring to actions performed on an object by a human hand) and non-manual action verbs (non-MA verbs). In a word detection task, participants were asked to react as quickly as possible when a word was presented. In experiment 1, we hypothesized that, for the compatibility judgment task, delayed judgment by constrained arm posture would be observed, particularly for manual action (MA) verbs but not for non-manual action (non-MA) verbs because only MA verbs are related to manual actions. In contrast, for the word detection task, constrained arm postures would not affect the judgment time. If the hypothesis would be the case, then it would show that peripheral bodily states affect the information processing of action verbs. The results of Experiment 1 showed that, for the compatibility judgment task, inconsistently in part with our hypothesis, constrained arm posture led to overall delayed responses. The results of the word detection task showed no significant main effect or interaction. This was consistent with our hypothesis and showed that constrained arm postures would not affect judgment time. This suggests that, in the compatibility judgment task, the delayed response induced by constrained arm posture was not merely due to the difficulty of responding via the button when the arm was constrained. The results of Experiment 2 produced the same results obtained in Experiment 1, showing the reliability of the findings. In Experiments 3 and 4, we addressed whether the effect of constrained arm posture would be reproduced when the compatibility judgment task was performed when the response method was changed from a finger response to a foot (Exp. 3) or voice (Exp. 4) response. The results showed that, when reacting with a foot, constrained arm posture did not lead to delayed reaction time. On the other hand, when reacting by voice, constrained arm posture led to delayed reaction times for both MA and non-MA verbs. These results partly supported our hypothesis that constrained arm posture would induce a delayed response in the compatibility judgment task; however, it depended on the reaction method. Inconsistently with our hypothesis, the result of the four experiments uniformly showed that delayed judgment was observed with constrained arm posture for both MA verbs and non-MA verbs. Before concluding that constrained arm posture is likely to affect the processing of verbs, regardless of the type of verb, an additional experiment was planned as Experiment 5 to exclude the possibility that the results were produced merely due to the experimental condition, in which a pictured stimulus of an object was presented before a verb. To exclude this possibility, we conducted an experiment in which the protocol was the same as in Experiments 1-4; however, the object and the verb were presented in reversed order. The results replicated the findings in Experiments 1-4. Experiment 6 showed that the effect of constrained arm posture was observed even for compatibility judgments for nouns. Based on the results of all experiments, we concluded that constrained arm posture could result in the peripheral bodily state's affecting the information processing of words. The effect of constrained arm posture was observed even when participants responded with their voices (Experiment 4), suggesting that the delayed judgment was not simply due to the difficulty of responding with the hand (i.e., the motor factor). In contrast to our hypothesis that constrained arm posture would affect only the information processing of manual action verbs, the results showed delayed processing of both manual action and non-manual action verbs when the arm posture was constrained. The results also showed delayed processing for nouns with constrained arm posture. The findings were discussed based on the idea that a body schema is involved in the information processing of action-related words.
首都大学東京, 2017-03-25, 博士（健康科学）, 甲第718号