Humans are capable of using the facial expression and bodily signals of others to give meaning to their words and understand how they are feeling. Currently, social interaction in real life has been more and more replaced with social interaction through social media. Not being able to see someone during a conversation has an effect on how the content of the conversation is interpreted. Processing the emotions of others relies on a number of mental processes and has an effect on behaviour. Being able to assess emotions correctly is essential for mental health. During social interaction we pay attention to subtle changes in facial expression and bodily movements of our partner. These changes are mostly unconscious, creating a reliable source that enables us to feel what the other feels by emotion contagion (taking over someone’s emotions). Facial mimicry, adjusting our faces to our partner, is an important factor for emotion contagion. This occurs mostly at an unconscious state. Support from the routines we use in recognizing facial expressions is the ‘inversion effect’: we have more difficulties in recognizing emotions when the face is shown upside down. Social perception is used as a broader term to refer to impressions and beliefs on what the other person is feeling, based on their facial expressions and bodily reactions.

Previous studies on emotions mostly used static facial expression. This is not a good representation of the dynamic nature of facial expressions and takes away other important cues (like bodily signals) we commonly use for interpreting emotions. High arousal is usually accompanied by sweating, blushing and dilated pupils. Facial reddening (not to be confused with blushing), is associated with the perfusion of the skin with oxygenated blood. We use this as a cue for health, but also to signal emotionality. Someone with reddened cheeks is usually perceived as dominant or angry/aggressive. Blushing is another form of facial reddening, and is seen is shy or anxious people. How reddening of the face is interpreted by others, and how one can separate reddening from blushing is a topic for future research.

Although the entire face shows signals of someone’s internal state, the eye region is seen as most powerful. Both adults and children focus their attention on the eyes when communicating with others. Gaze-direction and eye blinks are used as relevant cues, but studies have yet been inconclusive on the effects of these cues. Crying is also seen as a form of emotional expression. Over the years, two main functions of crying have been found. The first function is tension relief and promoting the recovery of homeostasis (both psychological and physiological). The second function is communication. Studies have found that crying communicates the need for emotional support and elicits empathy. Another social signal is pupil size. Dilating or contraction of the pupil is an autonomic reaction beyond our control. Studies have found that people with dilated pupils are more positively perceived.

Being able to show and perceive emotions has had an adaptive function through the evolution. Most research has focused on the eye region and facial muscles, but future research should also pay attention to other bodily signals that elicit emotion recognition.