Trends in Cognitive Sciences
OpinionBrain-to-brain coupling: a mechanism for creating and sharing a social world
Section snippets
Why two (or more) brains are better than one
Although the scope of cognitive neuroscience research is vast and rich, the experimental paradigms used are primarily concerned with studying the neural mechanisms of one individual's behavioral processes. Typical experiments isolate humans or animals from their natural environments by placing them in a sealed room where interactions occur solely with a computerized program. This egocentric framework is reminiscent of the Ptolemaic geocentric frame of reference for the solar system. From the
Brain-to-brain coupling
The premise of brain-to-brain coupling is that the perceptual system of one brain can be coupled to the motor system of another. This binding mechanism builds on a more rudimentary ability of brains to be coupled to the physical world (stimulus-to-brain coupling, Figure 1a). Different objects in the environment emit different forms of energy (mechanical, chemical, electromagnetic), and receptors convert these signals into electrical impulses that the brain can use to infer information about the
Acquiring communication
The emergence of any communication system, as Wittgenstein suggested [1], requires a shared understanding of the signals’ meaning (i.e. uses) within a particular context among a community of users. Such common ground is established through learning, which often takes place in the form of early interactions between a tutor's brain and a learner's brain. This hypothesis is supported by developmental evidence.
Many joint behaviors such as mating, group cohesion and predator avoidance depend on
Speech emerges through coupled oscillations
In the typical human scenario, much of communication is mediated by speech. How are speech signals transmitted and received when two adult individuals communicate? Notably, the transmission of information between two individuals is similar to reafferent forms of transmission of information between two areas within a single brain. Whereas it is typically thought that signals between parts of the brain require anatomical connections, neural states can also be influenced by physical signals that
Coordinated, hierarchical alignment during speech
Once brains are coupled to each other via speech signals, information can be shared and exchanged more efficiently. Human communication protocols can be divided into two types: monologues, in which only one speaker sends information and listeners receive it, and dialogues, in which interlocutors have to interweave their activities with precise timing. Garrod and Pickering argue that communication protocols in general, and dialogues in particular, are made easy because of the largely unconscious
Coupling of two brains via verbal communication
The coupling between the speaker's and listener's brain responses during natural communication relies on speaker–listener brain coupling. Using functional MRI, Stephens et al. recently recorded the brain activity of a speaker telling an unrehearsed real-life story [49]. Next, they measured the brain activity of a subject listening to the recorded audio of the spoken story, thereby capturing the time-locked neural dynamics from both sides of the communication. Finally, they asked the listeners
Coupling of two brains via nonverbal communication
Brain-to-brain coupling is also possible through hand gestures and facial expressions. This was first demonstrated in an experiment in which participants played the game ‘charades’ in the fMRI scanner. A signaler had to transmit nonverbal cues about the identity of a word while her brain activity was measured and her hand gestures were video recorded [56]. Later, an observer was shown the video footage while his brain activity was measured. Using between-brain Granger causality (Figure 4), the
Synergy through joint action
Coupled systems can generate complex behaviors that cannot be performed in isolation. Many human actions, such as playing basketball or operating a sailboat, require tight spatiotemporal coordination across team members [60]. Moreover, even actions that can be performed in isolation, such as playing a musical instrument or dancing, are faster and more accurate when performed within an ensemble.
An increasing body of evidence shows that, during joint actions, people become implicitly coupled at
Joint decision making
The choices an individual makes are often influenced and modified by the decisions of others. Individuals playing a strategy game keep track not only of the actions of the opponent but also of how opponents are influenced in response to their own actions [67]. For example, while playing the game ‘rock–paper–scissors’, players automatically imitate each other's strategic decisions when competing, although imitation does in fact reduce the chance of winning [68]. The influence of one brain on the
Concluding remarks
The structure of the shared external environment shapes neural responses and behavior. Some aspects of the environment are determined by the physical environment. Other aspects, however, are determined by a community of individuals, who together establish a shared set of rules (behaviors) that shape and constrain the perception and actions of each member of the group. For example, human infants undergo a period of perceptual narrowing whereby younger infants can discriminate between social
Acknowledgements
U.H. was supported by the National Institute of Mental Health award (R01MH094480). A.A.G. was supported by the National Institute of Neurological Disorders and Stroke (R01NS054898) and the James S. McDonnell Scholar Award. B.G. was supported by the National Science Foundation (BCS-1026943). C.K. was supported by a national initiative for the brain and cognition Netherlands Organization for Scientific Research (NWO) grant (433-09-253). S.G. was supported by the UK Economic and Social Research
References (76)
Dynamics of active sensing and perceptual selection
Curr. Opin. Neurobiol.
(2010)- et al.
Expanding the mirror: vicarious activity for actions, emotions, and sensations
Curr. Opin. Neurobiol.
(2009) - et al.
Social interaction, sensitive phases and the song template hypothesis in the white-crowned sparrow
Anim. Behav.
(1984) Temporal properties of spontaneous speech – a syllable-centric perspective
J. Phon.
(2003)The analysis of speech in different temporal integration windows: cerebral lateralization as ‘asymmetric sampling in time’
Speech Commun.
(2003)Neuronal oscillations and visual amplification of speech
Trends Cogn. Sci.
(2008)Endogenous cortical rhythms determine cerebral specialization for speech perception and production
Neuron
(2007)- et al.
Phase patterns of neuronal responses reliably discriminate speech in human auditory cortex
Neuron
(2007) - et al.
Is neocortex essentially multisensory?
Trends Cogn. Sci.
(2006) - et al.
Why is conversation so easy?
Trends Cogn. Sci.
(2004)