There is mounting evidence suggesting that, when we see someone expressing an emotion, say, anger, it triggers the same kind of activity in our brain as if we expressed that emotion ourselves ((Foroni & Semin, 2009; Martinez & Koenig, 2006). Furthermore, it looks like hearing a word with an underlying positive or negative emotion, like the words “party” or “kill” respectively, can trigger movements of the facial muscles that would correspond to the underlying emotions (Niedenthal, Winkielman, Mondillon, & Vermeulen, 2009). All in all then, it seems that having someone around us express an emotion “primes” that emotion in us.
My student Jennifer Harding and I examined this question behaviorally by briefly presenting facial expressions of anger, happiness, sadness, or neutrality then asking people to recognize pairs of emotional sounds presented dichotically (a different emotion to each ear). The sounds were words that were pronounced with an angry, happy, sad, or neutral emotional tone. With this approach, we found that the typical left ear advantage was quite large when the facial emotion matched with the left ear emotion, whereas the left ear advantage was considerably reduced when there was a match for the right ear (Harding & Voyer, 2015). Essentially, the facial expression primed activity in the brain in the areas where the emotions are processed (most likely in the right hemisphere) and this affected how people responded to the emotional sounds, potentially by biasing their attention to the left side of space as we speculated in our paper.
If we can demonstrate this type of effect in such an artificial situation and with a cross-modal context (i.e., a visual prime and an auditory target), imagine how emotions around you can affect your behavior. For starters, our data suggest that the emotions expressed by others around you affect how your respond to similar emotions. For example, if someone in your environment is angry, you are likely primed to recognize that emotion faster and more accurately than other emotions. Therefore, you might be more reactive to anger than to anything else. In addition, the emotions around you likely affect how you feel yourself. As I mentioned earlier, seeing someone express an emotion produces cerebral activation similar to what you would experience if you expressed the emotion yourself. If you already concluded from this that you would also feel the emotion to some extent, you reached a correct conclusion as this is what Wild, Erb, & Bartels (2001) reported in their research.
Imagine the consequences that this might have in everyday life. If you work in a hostile environment, it might make you hostile yourself! Thankfully, if you work in any context where there is a lot of smiling and happiness, it should help you feel happy (you might want to tell your boss about this). Similarly, there has been some research suggesting that living with a depressed roommate can make you feel depressed as well (Howes, Hokanson, & Loewenstein, 1985; Joiner, 1994). That should not be surprising: Essentially, if you see someone frowning and crying all the time, your brain response will trigger the same emotions in you, leading to a sense of depression.
In reality, everything I have discussed so far fits with the notion that emotions are embodied. Put simply, the idea underlying to whole concept of embodied cognition is that motor aspects of our body are used to process information and solve problems in our daily life. From this perspective, it makes sense that activating relevant brain areas and muscles would help us identify the emotions expressed by others. However, experiencing the same emotion to some extent as a result is a side effect of that process. So, in closing this post, I would encourage you to express more happiness than sorrow despite the curves that life throws at you. That will make everybody around you more positive as well!