This is a manuscript Chao and myself prepared for a “commentary”. We think NIRS based hyperscanning has a great potential on the shift from one-person neuroscience to 2-people neuroscience.
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Toward an Ecologically Valid Second-person Neuroscience: Hyperscanning with Near Infrared Spectroscopy
Chao Liu1 and Xu Cui2
1State Key Laboratory of Cognitive Neuroscience and Learning, Beijing Normal University, Beijing, China [email protected] http://psychbrain.bnu.edu.cn/teachcms/liuchao.htm
2 The Center for Interdisciplinary Brain Sciences Research, Stanford University, School of Medicine, USA [email protected] http://www.stanford.edu/~cuixu/
Abstract: We suggest that ecological validity is crucial for second-person neuroscience and to achieve it, the field need a transition from “face-to-screen neuroscience” to “face-to-face neuroscience”. We believe that the near infrared spectroscopy (NIRS) technique provides us a unique opportunity to such transition and use a NIRS-based hyperscanning study of human cooperation as a demonstration.
Expertise: Social neuroscience; near infrared spectroscopy (NIRS); hyperscanning
A key point of the second-person neuroscience approach is that the experimental design and data collection should be ecologically valid, which is crucial for “recreating the interaction dynamics of everyday-life social encounters”. However, the authors did not rigorously define “ecological validity” in terms of its meaning in second-person neuroscience, although it appears repeatedly in different sections of the target article. In this commentary we will suggest that the ultimate goal of ecological validity in the second-person neuroscience is to realize on-line monitoring of the face-to-face human social interaction, and near infrared spectroscopy (NIRS) is a promising technique to achieve this goal when combined with the hyperscanning technique.
From “face-to-screen neuroscience” to “face-to-face neuroscience”: Why is Ecological validity important in second-person neuroscience?
In psychology, ecological validity means “appropriate generalization from the laboratory to nonexperimental situations” (Brunswik, 1947). By this definition, most previous second-person neuroscience studies are not ecological valid for two reasons. First, people can hardly interact with each other when lying down in a noisy MRI scanner. Second, people seldom choose to communicate with each other through a computer screen when they can do it face to face. From the social psychology perspective, presenting another person’s face through computer screen (as most second-person neuroscience studies introduced in the target article have done) induces a confrontation of propinquity, that is, the physical proximity between people will influence their psychological proximity (Piercy & Piercy, 1972). In a face-to-screen setting, the physical proximity between participants is vague. Therefore, the social interaction between people in a face-to-screen setting might be interrupted by the propinquity effect and differ from what people actually do in a real life face-to-face condition.
The second problem is even more serious when we consider a recent study showing that our understanding of human mental states are greatly biased by the data collected solely from the WEIRD (Western, Educated, Industrialized, Rich, Democratic) populations (Henrich et al., 2010). Apparently, for people outside of the WEIRD world, interacting with a person in a computer screen is totally different from interacting with him face-to-face. In sum, to achieve an ecologically valid second-person neuroscience, the field should reconsider the limitations of face-to-screen settings and shift gradually to face-to-face settings.
Toward an ecologically valid second-person neuroscience: NIRS-based hyperscanning
In section 3.2.2 of the target article, the authors highlighted “hyperscanning” as a break-through technology for second-person neuroscience. However, they then stated that “While the application of this method has, indeed, provided invaluable insights into the neural basis of social cognition in conditions of health and pathology (e.g. King-Casas et al.2005, 2008), the approach never really caught on. At least in part this is due to the fact that using it to its full potential would have required establishing more ecologically valid ways for two or more participants to interact (cf. Redcay et al. 2010).”
One way to overcome this limitation is to combine hyperscanning with Near Infrared Spectroscopy. Compared with PET/fMRI /EEG/MEG, NIRS is a more suitable neural measurement for ecologically valid second-person neuroscience not only for its high sampling rate (~10 Hz) and good spatial resolution (1-3cm), but also for its high tolerance for movement, no distraction (e.g., no noise) and low requirement of preparation (e.g., no gel or water involved), and thus is much more comfortable for participants (Hoshi, 2007; Funane et al., 2011).
A recent study done by Cui et al (2012) demonstrates the advantage of NIRS-based hyperscanning in investigating social interactions. In this study, eleven pairs of participants were asked to play a computerized cooperation game side by side while their brains were scanned simultaneously using a NIRS device (Fig. 1A). In each trial, a “ready” signal appeared on the screen, followed by a “go” signal. The participants were instructed to press a button after the “go” signal. If they pressed the buttons simultaneously, they both won a point; otherwise they both lost a point. This experimental setting and neuroimaging results demonstrate three advantages of NIRS hyperscanning. First, the experiment was conducted in a naturalist environment where the participants sat side by side (Fig. 1A). Being able to measure human brain activity while people are freely interacting, including face-to-face conversation, is an important advantage of NIRS in terms of ecological validity (e.g. Suda et al. 2010, 2011). Second, the results showed that the coherence (a measure of correlation) between the measured NIRS signals in two brains increased during cooperation (Fig.1B). In contrast, no activation (measured as the signal amplitude) was found in either brain during cooperation. This indicates that hyperscanning reveals information that is not accessible by single-brain scanning. Third, such coherence increased during the second half of the cooperation experiment compared to that during the first half, indicating a learning effect. Learning is an important component during day-to-day social interactions. As learning is dynamic, the corresponding neural networks are expected to change over time. This change would be impossible to be discovered with a single-person scan if the change is manifested by the correlation between brains as the results indicated.
This study is a very good example of what can be done with NIRS and hyperscanning. High ecological validity, portability, low cost, and ease for hyperscanning setup make NIRS an ideal technology in the future second-person and even group social neuroscience. We look forward to seeing many more studies unveil the mystery of our social nature.
References
Some of the following papers can be found here.
Brunswik, E. (1947). Systematic and representative design of psychological experiments with results in physical and social perception. (Syllabus Series, No. 304) Berkeley: Univer. California Press,
Cui, X., Bryant, D. M., and Reiss, A. L. (2012). NIRS-based hyperscanning reveals increased interpersonal coherence in superior frontal cortex during cooperation. Neuroimage 59, 2430-7.
Funane T, Kiguchi M, Atsumori H, Sato H, Kubota K, Koizumi H. (2011). Synchronous activity of two people’s prefrontal cortices during a cooperative task measured by simultaneous near-infrared spectroscopy. Journal of Biomedical Optics, 16:77011.
Henrich, J., Heine, S.J., & Norenzayan, A. (2010). The weirdest people in the world? Behavioral and Brain Sciences, 33, 62–135.
Hoshi, Y. (2007). Functional near-infrared spectroscopy: current status and future prospects. Journal of Biomedical Optics, 12, 062106.
Piercy, F. P., & Piercy, S. K. (1972). Interpersonal attraction as a function of propinquity in two sensitivity groups. Psychology: A Journal of Human Behavior, 9(1), 27-30.
Suda, M., Takei, Y., Aoyama, Y., Narita, K., Sato, T., Fukuda, M. & Mikuni, M. (2010). Frontopolar activation during face-to-face conversation: An in situ study using near-infrared spectroscopy. Neuropsychologia 48(2):441-7.
Suda, M., Takei, Y., Aoyama, Y., Narita, K., Sakurai, N., Fukuda, M. & Mikuni, M. (2011). Autistic traits and brain activation during face-to-face conversations in typically developed adults. PLoS ONE 6(5):e20021.
