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Efficiently responding to others’ emotions, especially threatening expressions such as anger and fear, can have great survival value. Previous research has shown that humans have a bias toward threatening stimuli. Most of these studies focused on facial expressions, yet emotions are expressed by the whole body, and not just by the face. Body language contains a direct action component, and activates action preparation areas in the brain more than facial expressions. Hence, biases toward threat may be larger following threatening bodily expressions as compared to facial expressions. The current study investigated reaction times of movements directed toward emotional bodies and faces. For this purpose, a new task was developed where participants were standing in front of a computer screen on which angry, fearful, and neutral faces and bodies were presented which they had to touch as quickly as possible. Results show that participants responded faster to angry than to neutral stimuli, regardless of the source (face or body). No significant difference was observed between fearful and neutral stimuli, demonstrating that the threat bias was not related to the negativity of the stimulus, but likely to the directness of the threat in relation to the observer. Whereas fearful stimuli might signal an environmental threat that requires further exploration before action, angry expressions signal a direct threat to the observer, asking for immediate action. This study provides a novel and implicit method to directly test the speed of actions toward emotions from the whole body.
Humans are well adapted to quickly recognize and adequately respond to another’s emotional expression. As emotional expressions are intrinsically linked to actions, it has been proposed that in our attempt to understand emotions, we should study
The majority of emotion studies focus on facial expressions. However, faces are naturally encountered in the context of a whole body. Distinct expressions of emotion portrayed by body language are readily recognized even in the absence of facial and vocal cues (
Faces and bodies are processed by similar neural networks (
Although fear and anger are both negative emotions, a fearful signal can be more ambiguous and might signal an environmental threat, whereas anger can be perceived as a direct threat toward the observer requiring immediate action (
Thus far, fear and anger have never been directly compared in a task that requires direct actions toward these expressions. By using a new experimental paradigm, the current study investigates the speed of movements toward angry, fearful, and neutral facial and bodily expressions by male actors. We opted for the threat related emotions fear and anger for three reasons. First, both emotions can be expressed equally well via the body and the face, contrary to for example disgust that is not well recognized from body expressions alone, and happiness that is much better expressed by the face as compared to the body (
In real life, people seldom explicitly label other’s emotional expressions, yet this is what is most commonly asked during lab experiments. In explicit tasks such as emotion recognition tests, other cognitive processes such as memory and decision making can interfere with emotional processes such as action preparedness (for example, see
In the classical dot-probe task two emotional stimuli are presented simultaneously and are followed by a dot that is presented on the left or right side of the screen. Typically, participants are sitting in a chair and required to click on a left or right button on a keyboard or button box. What is generally measured is an attentional bias score, i.e., the extent to which reaction times are shortened when the dot was presented at the location of the emotional as compared to the neutral image. The aim of the current study is not to measure competition between two different stimuli, but to measure the speed of an action toward expressions and in addition, to provide a novel tool for future research. For that reason, we designed a simplified version of the emotional dot probe task where one image is presented at a time, on either the left or on the right side of the screen. To increase the naturalness of the study, a touch screen was used, in front of which participants were standing. Participants were requested to
Our expectations were threefold. First, we expected faster reaction times following threatening as compared to neutral stimuli. Second, bodies contain a direct action component and faces do not, which is why we expected faster responses toward fearful and angry bodies than toward faces. Third, in line with research showing greater activation of motor preparation areas in the brain and greater action preparedness following angry versus fearful stimuli, we predicted shorter reaction times following angry as compared to fearful bodies (
Thirty-three participants (12 male) took part in the experiment. The mean age was 23.23 (SD = 4.35), with age ranging from 18 to 35 years old. The participants were recruited at the psychology laboratory from the University of Amsterdam. They filled out an informed consent and were debriefed after the experiment for which they obtained course credit or money. Participants had no neurological or psychiatric history, were right-handed and had normal or corrected-to normal vision. The study was performed in accordance with the Declaration of Helsinki and approved by the local medical ethical committee.
After participants read the information brochure and signed the informed consent, they were given verbal instructions. In order to investigate the interference of bodily and facial expressions on the emotion task, angry, fearful, and neutral face or body expressions were randomly presented with Presentation software (Neurobehavioral Systems, San Francisco, CA, USA). Participants were asked to stand behind the touch screen (Figure
A trial started with the presentation of a dot in the middle, lower side of the screen, on which participants had to tap with their right hand. Because participants had to visually guide their hand action, this guaranteed that their eye fixation was on the location of the dot and that the hand did not occlude the upcoming stimulus. Immediately after participants touched the dot, the emotional picture was randomly presented on the left or on the right side of the screen. Participants were instructed to tap as fast as they could directly on the image, after which the image disappeared. Participants completed 192 trials which took about 5 min. Reaction times were measured from the moment the participant pressed the red dot in the center of the screen to the moment the participant pressed the image. See Figure
Pictures consisted of angry, fearful, and neutral body postures and facial expressions. The bodies were taken from the BEAST stimulus data base (
The study had a two within subjects (source: body/face) by three within subjects (emotion: anger, fear, or neutral) design.
The reaction time data was skewed (skewness = 12.813, SE = 0.032) and had outliers (maximum reaction time = 9930 ms, mean reaction time = 470 ms). The data was therefore filtered to exclude reaction times that were more than two standard deviations above each individuals mean reaction time. Next, a log-transformation was performed. After these steps, the issue of skewness was solved (skewness = 1.019, SE = 0.033) and inspections of the histograms and Shapiro–Wilks tests showed that each experimental condition was normally distributed (
A 3 (Emotion: Angry/Fear/Neutral) × 2 (Source: Face/Body) repeated measures ANOVA showed a main effect of emotion
Emotions are intrinsically linked to actions (
Many emotion studies have reported a threat bias in which threatening faces or scenes are prioritized over neutral (
Previous emotion studies mainly focused on faces. However, emotions are displayed in both the face and the body, the main difference being that bodies contain an action component and faces do not. We hypothesized that this action component would evoke faster actions in our participants, resulting in shorter response latencies when responding to bodies than to faces. Yet, no difference between bodies and faces was observed. Two explanations are possible. First, the results could indicate that it does not matter whether threat is displayed by the body or the face. A threat is a threat and it has evolutionary benefits to be able to quickly respond to that. Another explanation can be found in the nature of the stimulus material. Faces and bodies were not presented in true proportions: the size of the pictures was identical, which means that faces were displayed relatively larger than bodies. Bigger stimuli are seen as closer in distance and the relatively large faces may have therefore overshadowed a putative difference in reaction times between faces and bodies. To rule out this explanation, a future study should therefore present faces and bodies in true proportions.
In a previous study,
In the current study, the mechanism underlying the faster responses toward angry as compared to neutral stimuli remains speculative and might reflect enhanced attention (
The task employed in the current study required an approach-related movement. It is possible that different results can be obtained using an avoidance-related movement (
In sum, the current study made use of a new device that makes it possible to directly test actions toward (or away from) emotions. Results showed a threat bias for angry faces and bodies, which is in line with previous studies showing that threat cues are prioritized over neutral cues. There was no threat bias for fearful stimuli, suggesting that the directness of the threat in case of anger sped up reaction times, rather than the negativity of a stimulus. Also, no difference was found between responding to faces and bodies, suggesting that the threat bias is general and not restricted to one source. The current study supports the notion that evolution evolution prepared humans for fast actions when facing a threat.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
We thank Coos Hakvoort for fabricating the device. Research was supported by the Netherlands Science Foundation (VENI # 016-155-082) and The Royal Netherlands Academy of Arts and Sciences (KNAW) Dobberke Foundation for Comparative Psychology (# UPS/BP/4387 2014-3) to MK.
Conventionally, a test with a partial eta-squared (
A more liberal paired sample
A more lenient paired sample