The Effects of Meaning and Emotional Content of a Sentence on the Kinematics of a Successive Motor Sequence Mimiking the Feeding of a Conspecific

Abstract

Aim: Do the emotional content and meaning of sentences affect the kinematics of successive motor sequences?

Material and methods: Participants observed video-clips of an actor pronouncing sentences expressing positive or negative emotions and meanings (related to happiness or anger in Experiment 1 and food admiration or food disgust in Experiment 2). Then, they reached-to-grasp and placed a sugar lump on the actor's mouth. Participants acted in response to sentences whose content could convey (1) emotion (i.e., face expression and prosody) and meaning, (2) meaning alone, or (3) emotion alone. Within each condition, the kinematic effects of sentences expressing positive and negative emotions were compared. Stimuli (positive for food admiration and negative for food disgust), conveyed either by emotion or meaning affected similarly the kinematics of both grasp and reach.

Results: In Experiment 1, the kinematics did not vary between positive and negative sentences either when the content was expressed by both emotion and meaning, or meaning alone. In contrast, in the case of sole emotion, sentences with positive valence made faster the approach of the conspecific. In Experiment 2, the valence of emotions (positive for food admiration and negative for food disgust) affected the kinematics of both grasp and reach, independently of the modality.

Discussion: The lack of an effect of meaning in Experiment 1 could be due to the weak relevance of sentence meaning with respect to the motor sequence goal (feeding). Experiment 2 demonstrated that, indeed, this was the case, because when the meaning and the consequent emotion were related to the sequence goal, they affected the kinematics. In contrast, the sole emotion activated approach or avoidance toward the actor according to positive and negative valence. The data suggest a behavioral dissociation between effects of emotion and meaning.

Keywords: emotion; human kinematics; meaning; prosody; spoken sentences; voice spectra.

FIGURE 1

Task and procedure of Experiments 1 and 2. The upper part of the figure presents a participant during the execution of reaching-grasping and placing a sugar lump on a container below the mouth of the acress presented by a PC display. Points represent the hand trajectory of the motor sequence. The lower part of the figure represents the procedures of Experiments 1 and 2.

FIGURE 2

Experiment 1. Parameters of hand kinematics of the participants and voice spectra of sentences presented to a conspecific by a video. Upper row: variation in reach peak acceleration and velocity of participants during reaching-grasping and placing a sugar lump on the conspecific’s mouth. The sentence features could be meaning and emotion, meaning only, or emotion only, whereas the sentence valence could be either positive or negative. Lower row: variation in pitch and intensity of the voice of the actress pronouncing the sentences when feature and valence varied. PV, positive valence; NV, negative valence. Significances between positive and negative valence for each feature are only reported.

FIGURE 3

Experiment 2. Significant voice spectra parameters of sentences pronounced aloud by the actress. They were the following: intensity and sentence duration. FD, food disgust; FA, food admiration. Whiskers are SE, horizontal bars indicate statistical significance.

FIGURE 4

Experiment 2. Parameters of hand kinematics of the participants during performing the feeding sequence. They were the following: peak velocity of finger opening and closing, reach peak velocity, and acceleration. Other conventions as in Figures 2 and 3.