Witnessing two lovers reunite on screen elicits feelings of happiness. Watching someone throw up triggers feelings of disgust. It's generally accepted that these emotions are categorically distinct from one another in our minds and new research shows our bodily responses to specific emotions may also be distinct. The study was published today in the Proceedings of the National Academy of the Sciences.
What triggers conscious emotional feelings has long been a topic of debate among scientists. "We often get a sensation of 'I am happy now or I am sad now.' So where do these [feelings] arise from?" asks Dr. Lauri Nummenmaa, assistant professor in Cognitive Neuroscience at the Aalto University School of Science in Finland. Uncovering the source of physical activity is what Nummenmaa sought to accomplish.
Some scholars believe that a feeling of anger, for example, triggers changes in our body's responses and that when we become aware of these changes, that awareness actually helps us to construct conscious representations of a feeling, says Nummenmaa.
"We often think the emotions are something that happen only in the mind, but there's also lots of evidence suggesting that they also happen in our bodies," says Nummenmaa. In order to understand whether anger is qualitatively different from happiness at the body level, and not just the mind level, Nummenmaa had to design the right type of study.
This mind-body connection isn't news to scientists. However, there is still disagreement over whether changes in body activity associated with certain emotions are specific enough to be identified as "discrete emotional feelings" and whether these sensations actually contribute to the conscious emotional experience.
"Our data show bodily sensations associated with different emotions are so specific that, in fact, they could at least in theory contribute significantly to the conscious feeling of the corresponding emotion," says Nummenmaa.
Dr. Antonio Damasio, director of the Brain and Creativity Institute at the University of Southern California, and an expert in consciousness, said the study provided compelling evidence to support his and his colleagues claims "that the content of emotion is largely based on the perception of body states."
The Finnish researchers studied 701 subjects, asking them what they felt in their bodies as they experienced 13 different basic and complex emotions. Nummenmaa and his colleagues used four different experiments involving between 36 and 302 subjects for each. In the first experiment, researchers simply asked subjects which body sensations they associated with certain emotions. In two other experiments, subjects watched excerpts from Hollywood movies and read stories that were meant to induce specific emotions. In the last experiment they showed subjects pictures of facial expressions that appeared happy, sad or some type of other emotion, and asked the subjects to judge how people in the pictures would feel in their bodies.
The subjects were shown two silhouettes of the human figure on a computer. On one figure they were asked to color in areas of the body where activity increased. On the second figure, they colored in the areas of the body where activity decreased.
Using warm and cool colors, the body maps reflect the subjects' bodily experience of an emotion. As these images indicate, feeling happiness increased activity throughout the body and particularly in, the chest area and head. This might reflect an increased heart rate and more rapid breathing, the study noted. In contrast, feelings of depression were marked entirely in black and blue, the cool colors reflecting an overall decrease in bodily responses. Nummenmaa clarified that the subjects, according to their own report, were all healthy. The experiment reflected feelings of depression and not a clinically diagnosed state.
From an evolutionary perspective, emotions developed as a way to draw organisms either away from trouble or towards positive, pleasurable events, says Nummenmaa. Seen in this context, the similarities in the body maps of anger and happiness make sense, according to the study. Representations of both emotions show increased activity in the arms and to a lesser extent the feet. Both anger and happiness are approach-related emotions as opposed to avoidance-related emotions such as fear or disgust. So an increase in activity in the arms and feet seems fitting.