Because they are likely to trigger convergent emotional reactions in observers, it has become extremely common to refer to emotions as ‘contagious’ elements. While it could have simply remained a metaphor, the concept of contagion has become central to account for situations of emotional convergence between individuals. In this respect, the primitive emotional contagion model introduced by Hatfield and colleagues in 1994 assumes that we have a strong tendency to mimic the facial, postural and vocal motor behaviour of the people we interact with. This claim resembles the shared representations framework, according to which we make use of our own motor resources to access and share others’ states. This chapter consists of a critical review of the primitive emotional contagion model and further discusses the legitimacy of considering emotions as contagious elements to describe situations of affective or emotional convergence.

With the renewed interest in perception–action coupling at the cerebral level, this idea of shared representations has rapidly been extended to non-motor domains as well, including somatosensory experiences. Indeed, in the last decades, a wealth of evidence has been produced suggesting that experience of somatosensory stimulations such as touch and pain share common neurophysiological and cognitive representations with the perception of the same experiences in others. However, it remains unclear what exactly is shared between an individual experiencing a state and someone observing this individual, and to what extent non-motor shared representations are supported by evidence. Here, we first review the different definitions of shared representations in the somatosensory domain proposed in the cognitive neuroscience literature. We then briefly describe the neurophysiological mechanisms underlying pain and touch perception and provide a critical review of the evidence for and against shared somatosensory representations for the different aspects of pain and touch experiences. Finally, we argue that these shared somatosensory representations can be modulated by individual, relational and contextual characteristics, and while most of these modulations occur implicitly, some can be deliberate, focused and meant to optimize subsequent social interactions.

This volume discusses the evidence for – and implications of – the existence of shared representations in the human brain. When we perceive another person’s actions, emotional states or even tactile sensations, we activate the same motor programs, emotional circuitry and somatosensory networks that would be active if we were to perform those actions, or feel those emotions or sensations. Thus our own representation of an action, emotion or sensation becomes ‘shared’: activated not only by our own action, emotion or touch, but also by the perception of the same events in other people. There is now extensive evidence, discussed in earlier chapters, for the presence of such ‘shared representations’; in contrast, what this chapter addresses is how the brain acquires these shared representations. In this chapter, I focus on shared representations of action, as instantiated by mirror neurons. This is because historically it is shared action representations that have been subject to the most investigation; however, I will conclude with some thoughts on how this work may generalize to other types of shared representation.

To survive, we must interact with an ever-changing world. Our capacity to move accurately in a range of environments lies in the brain’s ability to flexibly modify our motor behavior. For example, simply holding an object in the hand changes the arm’s dynamic environment. That is, the additional weight of the object changes the relationship between applied forces and motion such that the brain’s motor commands and muscle forces no longer result in the intended arm movement. In order to skillfully manipulate the object, the brain must alter its motor commands to compensate for the object’s weight and achieve a desired movement. Subsequent movements are improved with time and practice; this process is called motor learning. While many of our motor skills are acquired and refined through active physical practice, we can also learn how to make movements by observing others. This is referred to as observational motor learning. This chapter will begin with a brief overview of modern studies of human motor learning, followed by a discussion of how these concepts relate to observational motor learning.

Human beings come into the world wired for social interaction. At the fourteenth week of gestation, twin fetuses already display interactive movements specifically directed towards their co-twin. Readiness for social interaction is also clearly expressed by the newborn who imitates facial gestures, suggesting that there is a common representation mediating action observation and execution. While actions that are observed and those that are planned seem to be functionally equivalent, it is unclear if the visual representation of an observed action inevitably leads to its motor representation. This is particularly true with regard to complementary actions (from the Latin complementum; i.e. that fills up), a specific class of movements which differ, while interacting, with observed ones. In geometry, angles are defined as complementary if they form a right angle. In art and design, complementary colors are color pairs that, when combined in the right proportions, produce white or black. As a working definition, complementary actions refer here to any form of social interaction wherein two (or more) individuals complete each other’s actions in a balanced way. Successful complementary interactions are founded on the abilities: (1) to simulate another person’s movements; (2) to predict another person’s future action/s; (3) to produce an appropriate congruent/incongruent response that completes the other person’s action/s; and (4) to integrate the predicted effects of one’s own and another person’s actions. It is the neurophysiological mechanism that underlies this process which forms the main theme of this chapter.