How can I credibly commit to others?

Francesca Bonalumi – PhD candidate, Department of Cognitive Science, Central European University

 

 

Imagine that you plan to go to the gym with your friend Kate. You decide together to meet in the locker room at 6pm. Why would you expect that Kate will honour this agreement to meet you at the gym? Now, imagine that at 5.30pm you discover that some other friends are gathering at 6pm, and you would love to join them. What restrains you from joining them, even if this is now your preferred option? Your answers to these kinds of dilemmas that are faced in everyday life will probably involve some reference to the fact that a commitment was in place between you and Kate.

The notion of a commitment is worth investigating, in part, because it applies to such a wide variety of cases: we are committed to our partners, our faith, our work, our promises, our goals, and even ourselves. Although there is an obvious similarity between all these situations, I will restrict this post to instances of interpersonal commitment, namely those commitments that are made by one individual to another individual (cfr. Clark 2006). According to a standard philosophical definition of interpersonal commitment, a commitment is a relation among one committed agent, one agent to whom the commitment has been made, and an action which the committed agent is obligated to perform (Searle 1969; Scanlon 1998).

The ability to make and assess interpersonal commitments is crucial in supporting our prosocial behaviour: being motivated to comply with those courses of action that we have committed to, and being able to assess whether we can rely on others’ commitments, enables us to perform a wide range of jointly coordinated and interpersonal activities that wouldn’t otherwise be feasible (Michael & Pacherie, 2015). This ability requires psychological mechanisms that induce individuals to follow rules or plans even when it is not in their short-term interests: this can sustain phenomena from the inhibition of short-term self-interested actions to the motivation for moral behaviour. I will focus on one key, yet underappreciated, aspect of this relation which sustains the whole act of committing: how the committed agent gives assurance to the other agent that she will perform the relevant action. That is, how she makes her commitment credible.

Making a commitment can be defined as an act that aims to influence another agent’s behaviour by changing her expectations (e.g. my committing to help a friend influences my friend’s behaviour, insofar as she can now rely on my help), and by this act the committer gains additional motivation for performing the action that she committed to (Nesse 2001; Schelling 1980). The key element in all of this is credibility: how do I credibly persuade someone that I will do something that I wouldn’t do otherwise? And why would I remain motivated to do something that is no longer in my interest to do? Indeed, a dilemma faced by recipients in any communicative interaction is determining whether they can rely on the signal of the sender (i.e. how to rule out the possibility that the sender is sending a fake signal) (Sperber et al., 2010). Likewise, in a cooperative context the problem for any agent is how to distinguish between a credible commitment and a fake commitment, and how to signal a credible commitment without being mistaken for a defector (Schelling, 1980).

The most persuasive way to make my commitment credible is to discard alternative options in order to change my future incentives, such that compliance with my commitments will remain in my best interests (or be my only possible choice). Odysseus instructing his crew to tie him to the mast of the vessel and to ignore his future orders is one strong example of committing to resist the Sirens’ call in this manner; avoiding coffee while trying to quit smoking (when having a cigarette after a coffee was a well-established habit) is another example.

How can we persuade others that our commitments are credible when incentives are less tangible, and alternative options cannot be completely removed? Consider a marriage, in which both partners rely on the fact that the other will remain faithful even if future incentives change. Emotions might be one way of signalling my willingness to guarantee the execution of the commitment (Frank 1998; Hirshleifer 2001). If two individuals decide to commit to a relationship, the emotional ties that they form ensure that neither will reconsider the costs and benefits of the relationship[1].  Likewise, if, during a fight, one individual displays uncontrollable rage, she is giving her audience reason to believe that she won’t give up the fight even if continuing to fight is to her disadvantage. One reason that emotions are taken to be credible is because they are allegedly hard to convincingly fake: some studies suggest that humans are intuitively able to recognize the appropriate emotions when observing a face (Elfenbein & Ambady, 2002), and to some extent humans are able to effectively discriminate between genuine and fake emotional expression (Ekman, Davidson, & Friesen, 1990; Song, Over, & Carpenter, 2016).

Formalising a commitment by making promises, oaths or vows is another way of increasing the credibility of your commitment. Interestingly, with such formalised declarations people not only manifest an emotional attachment to the object of the commitment; they also signal a willingness to put their reputation at risk. This is because the more public the commitment is (and the more people are aware of the commitment), the higher the reputational stakes will be for the committed individual.

Securing a commitment by altering your incentives, by risking your reputation, or by expressing it via emotional displays are importantly similar: the original set of material payoffs for performing each action changes, because now the costs of smoking or untying yourself from the mast of a vessel are too high (if it is even still possible to pay these costs). But we can imagine the emotional costs paid in case of a failure (e.g. the disappointment from slipping back into our undesirable habit of smoking), as well as the social costs (e.g. damage to our reputation as a reliable individual), as incentives to comply with the action that was committed to (Fessler & Quintelier 2014).

 

 

Cheating Non-cheating
Before the commitment p -p
After the commitment p – (m + r + e) -p

Fig.1 Payoff matrix of the decision to cheat on your partner: p is the pleasure you get out of cheating, whereas m is the material costs paid in such cases (e.g. a costly divorce), r is the reputational costs and e is the emotional burden that will be paid in such cases. When p is not higher than the sum of r, m and e, and the individual accurately predict the likelihood of these outcomes, we’ll have a situation in which breaking a commitment is not worthwhile.

 

Consistent with the idea that commitments change your payoff matrix (see Fig.1), several studies have shown that commitments facilitate coordination and cooperation in multiple economic games. Promises were found to increase an agent’s trustworthy behaviour as well as her partner’s predictions about her behaviour in a trust game (Charness and Dufwenberg 2006), and they were found to increase one’s rates of donations in a dictator game (Sally 1995; Vanberg 2008). Spontaneous promises have also been found to be predictive of cooperative choices in a Prisoner’s Dilemma game (Belot, Bhaskar & Van de Ven 2010). The willingness to be bound to a specific course of action (e.g. as Ulysses) has also been found to be highly beneficial in Hawk-Dove and Battle-of-Sexes games, as committed players are more likely to obtain their preferred outcomes (Barclay 2017).

Interestingly, the payoff structures that an agent faces when they make a commitment is similar to the payoff structure of a threat: If you are involved in a drivers’ game of chicken, the outcome you want is the one in which you don’t swerve. But your partner prefers the outcome in which she does not swerve, and the worst outcome would be the one in which the two cars crash because neither of you swerved. The key factor is, again, whether you can credibly signal to the other driver that you won’t spin the wheel, no matter what.

Some of the same means by which credibility can be conveyed in cases commitment apply to threats as well. For instance, one efficacious way by which you can credibly persuade the other driver is by removing the steering wheel and throwing it out of the window, thereby physically preventing yourself from changing the direction of your car (Kahn 1965); another is by playing a war of nerves, conveying the idea that you are so emotionally connected to your goal that you would be willing to pay the highest cost if necessary.

Threat is an interesting phenomenon to consider when investigating the role of credibility in commitment because it might help us to understand how commitment works, and how threat and commitment might have evolved in similar fashion. What leads a non-human animal to credibly signal an intention to behave in a certain way to its audience, and what lead its audience to rely on this signal, is highly relevant for investigating commitment. It is still uncertain just how threat signals have stabilized evolutionarily, given that a selective pressure for faking the threat would also be evolutionarily advantageous (Adams & Mesterton-Gibbons 1995). The same selective pressure apply to human threats and commitments: if the goal is to signal future compliance to an action in order to change the audience’s behaviour (by changing her expectations), what motivates us to then comply to that signal instead of, say, simply taking advantage of the change in our audience’s behaviour?

In other words, the phenomenon of commitment is intrinsically tied to the problem of recognising (and maybe even producing) fake signals, and deceiving others, just as in the case of making a threat. That being said, it is worth keeping in mind that the phenomenon of threat differs importantly from the phenomenon of commitment, insofar as the former does not entail any motivation for prosocial behaviour. In this respect, the phenomena of quiet calls and natal attraction, in which animals signal potential cooperation or a disposition not to engage in a fight, are also worth investigating further for the sake of better understanding how credibility can be established in the case of commitment (Silk 2001).

Most of our social life is built upon commitments that are either implicit or explicitly expressed. We expect people to do things even in the absence of a verbal agreement to do so, and we act in accordance with these expectations. Investigating the factors that carry this motivational force, such as credibility, is the next big challenge in better grasp the complexities of this important notion, and would help us to better understand its ontogenetic and phylogenetic development.

 

REFERENCES

Adams, E. S., & Mesterton-Gibbons, M. (1995). The cost of threat displays and the stability of deceptive communication. Journal of Theoretical Biology, 175(4), 405–421.

Barclay, P. (2017). Bidding to Commit. Evolutionary Psychology, 15(1), 1474704917690740.

Belot, M., Bhaskar, V., & van de Ven, J. (2010). Promises and cooperation: Evidence from a TV game show. Journal of Economic Behavior & Organization, 73(3), 396-405.

Charness, G., & Dufwenberg, M. (2006). Promises and Partnership. Econometrica, 74, 1579–1601.

Clark, H. H. (2006). Social actions, social commitments. In S.C. Levinson, N.J. Enfield (Eds.), Roots of human sociality: Culture, cognition and interaction, (pp. 126-150). New York: Bloomsbury.

Ekman, P., Davidson, R. J., & Friesen, W. V. (1990). The Duchenne smile: Emotional expression and brain physiology: II. Journal of Personality and Social Psychology, 58(2), 342–353.

Elfenbein, H. A., & Ambady, N. (2002). On the universality and cultural specificity of emotion recognition: A meta-analysis. Psychological Bulletin, 128(2), 203–235.

Fessler, D. M. T., & Quintelier, K. (2014). Suicide Bombers, Weddings, and Prison Tattoos. An Evolutionary Perspective on Subjective Commitment and Objective Commitment. In R. Joyce, K. Sterelny, & B. Calcott (Eds.), Cooperation and its evolution (pp. 459–484). Cambridge, MA: The MIT Press.

Frank, R. H. (1988). Passion within reason. New York, NY: W.W. Norton & Company.

Hirshleifer, J. (2001). On the Emotions as Guarantors of Threats and Promises. In The Dark Side of the Force: Economic Foundations of Conflict Theory (pp. 198–219). Cambridge, MA: Cambridge University Press.

Kahn, H. (1965). On Escalation: Metaphors and Scenarios. New York, NY: Praeger Publ. Co.

Michael, J., & Pacherie, E. (2015). On Commitments and Other Uncertainty Reduction Tools in Joint Action. Journal of Social Ontology, 1(1).

Nesse, R. M. (2001). Natural Selection and the Capacity for Subjective Commitment. In R. M. Nesse (Ed.), Evolution and the Capacity for Commitment (pp. 1–43). New York, NY: Russell Sage Foundation.

Sally, D. (1995). Conversation and cooperation in social dilemmas a meta-analysis of experiments from 1958 to 1992. Rationality and society, 7(1), 58-92.

Scanlon, T. M. (1998). What We Owe to Each Other. Cambridge, MA: Harvard University Press.

Schelling, T. C. (1980). The Strategy of Conflict. Cambridge, MA: Harvard University Press.

Searle, J. R. (1969). Speech Acts: An essay in the philosophy of language. Cambridge, MA: Cambridge University Press.

Silk, J. B. (2001). Grunts, Girneys, and Good Intentions: The Origins of Strategic Commitment in Nonhuman Primates. In R. M. Nesse (Ed.), Evolution and the Capacity for Commitment (pp. 138–157). New York, NY: Russell Sage Foundation.

Song, R., Over, H., & Carpenter, M. (2016). Young children discriminate genuine from fake smiles and expect people displaying genuine smiles to be more prosocial. Evolution and Human Behavior, 37(6), 490–501.

Sperber, D., Clément, F., Heintz, C., Mascaro, O., Mercier, H., Origgi, G., & Wilson, D. (2010). Epistemic vigilance. Mind and Language, 25(4), 359–93.

Vanberg, C. (2008). Why Do People Keep Their Promises? An Experimental Test of Two Explanations. Econometrica, 76(6), 1467–1480.

 

[1] Indeed, marriage itself may be a way of increasing the likelihood that a commitment will be respected in the future. This is because formalising the relationship in this manner increases the exit costs of a relationship.

Is the Future More Valuable than the Past?

Alison Fernandes – Post-Doctoral Fellow on the AHRC project ‘Time: Between Metaphysics and Psychology’, Department of Philosophy, University of Warwick

Inline images 2

 

We differ markedly in our attitudes towards the future and past. We look forward in anticipation to tonight’s tasty meal or next month’s sunny holiday. While we might fondly remember these pleasant experiences, we don’t happily anticipate them once they’re over. Conversely, while we might dread the meeting tomorrow, or doing this year’s taxes, we feel a distinct sort of relief when they’re done. We seem to also prefer pleasant experiences to be in the future, and unpleasant experiences to be in the past. While we can’t swap tomorrow’s meeting and make it have happened yesterday, we might prefer that it had happened yesterday and was over and done with.

Asymmetries like these in how we care about the past and future can seem to make a lot of sense. After all, what’s done is done, and can’t be changed. Surely we’re right to focus our care, effort and attention on what’s to come. But do we sometimes go too far in valuing past and future events differently? In this post I’ll consider one particular temporal asymmetry of value that doesn’t look so rational, and how its apparent irrationality speaks against certain metaphysical ways of explaining the asymmetry.

Eugene Caruso, Daniel Gilbert, and Timothy Wilson, investigated a temporal asymmetry in how we value past and future events (2008). Suppose that I ask you how much compensation would be fair to receive for undertaking 5 hours of data entry work. The answer that you give seems to depend crucially on when the work is described as taking place. Subjects judged that they should receive 101% more money if the work is described as taking place one month in the future ($125.04 USD on average), compared to one month in the past ($62.20 USD on average). Even for purely hypothetical scenarios, where no one actually expects the work to take place, we judge future work to be worth much more than past work.

This value asymmetry appears in other scenarios as well (Caruso et al., 2008). Say your friend is letting you borrow their vacation home for a week. How expensive a bottle of wine do you buy as a thank you gift? If the holiday is described as taking place in the future, subjects select wine that is 37% more expensive. Suppose that you help your neighbour move. What would be an appropriate thank you gift for you to receive? Subjects judge they should receive 71% more expensive bottles of wine for helping in the future, compared to the past. Say you’re awarding damages for the suffering of an accident victim. Subjects judge that victims should be awarded 42% more compensation when they imagine their suffering as taking place in the future, compared to the past.

Philosophers like Craig Callender (2017) have become increasingly interested in the value asymmetry studied by Caruso and his colleagues. This is partly because there has been a long history of using asymmetries in how we care about past and future events to argue for particular metaphysical views about time (Prior, 1959). For example, say you hold a ‘growing block’ view of time, according to which the present and past exist (and are therefore ‘fixed’) while future events are not yet real (so the future is unsettled and ‘open’). One might argue that a metaphysical picture with an open future like this is needed to make sense of why we care about future events more than past events. If past events are fixed, they’re not worth spending our time over—so we value them less. But because future events are up for grabs, we reasonably place greater value in them in the present.

Can one argue from the value asymmetry Caruso and his team studied, to a metaphysical view about time? Much depends on what features the asymmetry has, and how these might be explained. When it comes to explaining the temporal value asymmetry, Caruso and his team discovered that it is closely aligned to another asymmetry: a temporal emotional asymmetry. More specifically, we tend to feel stronger emotions when contemplating future events, compared to contemplating past events.

These asymmetries are correlated in such a way as to suggest the emotional asymmetry is a cause of the value asymmetry. Part of the evidence comes from the fact that the emotional and value asymmetry share other features in common. For example, we tend to feel stronger emotions when contemplating our own misfortunes, or those of others close to us, than we do contemplating the misfortune of strangers. The value asymmetry shares this feature. It is also much more strongly pronounced for events that concern oneself, compared to others. Subjects judge their own 5 hours of data entry work to be worth nearly twice as much money when it takes place in the future, compared to the past. But they judge the equivalent work of a stranger to be worth similar amounts of money, independently of whether the work is described as taking place in the future or in the past.

The same features that point towards an emotional explanation of the value asymmetry also point away from a metaphysical explanation. The value asymmetry is, in a certain sense, ‘perspectival’—it is strongest concerning oneself. But if metaphysical facts were to explain why future events were more valuable than past ones, it would make little sense for the asymmetry to be perspectival. After all, on metaphysical views of time like the growing block view, events are either future or not. If future events being ‘open’ is to explain why we value them more, the asymmetry in value shouldn’t depend on whether they concern oneself or others. Future events are not only open when they concern me – they are also open when they concern you. So the metaphysical explanation of the value asymmetry does not look promising.

If we instead explain the value asymmetry by appeal to an emotional asymmetry, we can also trace the value asymmetry back to further asymmetries. Philosophers and psychologists have given evolutionary explanations of why we feel stronger emotions towards future events than past events (Maclaurin & Dyke, 2002; van Boven & Ashworth, 2007). Emotions help focus our energies and attention. If we generally need to align our efforts and attention towards the future (which we can control) rather than being overly concerned with the past (which we can’t do anything about), then it makes sense that we’re geared to feel stronger emotions when contemplating future events than past ones. Note that this evolutionary explanation requires that our emotional responses to future and past events ‘overgeneralise’. Even when we’re asked about future events we can’t control, or purely hypothetical future events, we still feel more strongly about them than comparative past events, because feeling more strongly about the future in general is so useful when the future events are ones that we can control.

A final nail in the coffin for a metaphysical explanation of the value asymmetry comes from thinking about whether subjects take the value asymmetry to be rational. I began with some examples of asymmetries that do seem rational. It seems rational to prefer past pains to future ones, and to feel relief when unpleasant experiences are over. Whether asymmetries like these are in fact rational is a topic of controversy in philosophy (Sullivan, forth.; Dougherty, 2015). Regardless, there is strong evidence that the value asymmetry that Caruso studied is taken to be irrational, even by subjects whose judgements display the asymmetry.

The methodology Caruso used involved ‘counterbalancing’: some subjects were asked about the future event first, some were asked about the past event first. When the results within any single group were considered, no value asymmetry was found. That is, when you ask a single person how they value an event (say, using a friend’s vacation home for a week) they think its value now shouldn’t depend on whether the event is in the past or future. It is only when you compare results across the two groups that the asymmetry emerges (see Table 1). It’s as if we apply a consistency judgement and think that future and past events should be worth the same. But when we can’t make the comparison, we value them differently. This strongly suggests that the asymmetry is not being driven by a conscious judgement that the future is really is worth more than the past, or by a metaphysical picture according to which it is. If it were, we would expect the asymmetry to be more pronounced when subjects were asked about both the past and the future. Instead, the asymmetry disappears.

 

Order of evaluation
Use of a friend’s vacation home Past event first Future event first
Past $89. 17 $129.06
Future $91.73 $121.98

Table 1: Average amount of money (USD) that subjects judge they would spend on a thank you gift for using a friend’s vacation home in the past or future (Caruso et al., 2008).

 

Investigations into how temporal asymmetries in value arise are allowing philosophers and psychologists to build up a much more detailed picture of how we think about time. It can seem intuitive to think of the past as fixed, and the future as open. Such intuitions have long been used to support certain metaphysical views about time. But, while metaphysical views might seem to rationalise asymmetries in our attitudes, their actual explanation seems to lie elsewhere, in much deeper evolution-driven responses. We may even be adopting metaphysical views as rationalisers of our much more basic emotional responses. If this is right, the value asymmetry not only provides a case study of how we can get by explaining asymmetric features of our experience without appeal to metaphysics. It suggests that psychology can help explain why we’re so tempted towards certain metaphysical views in the first place.

 

REFERENCES

Callender, Craig. 2017. What Makes Time Special. Oxford: Oxford University Press.

Caruso, Eugene M. Gilbert, D. T., and Wilson, T. D. 2008. A wrinkle in time: Asymmetric valuation of past and future events. Psychological Science 19(8): 796–801.

Dougherty, Tom. 2015. Future-Bias and Practical Reason. Philosophers’ Imprint. 15(30): 1−16.

Maclaurin, James & Dyke, Heather. 2002. ‘Thank Goodness That’s Over’: The Evolutionary Story. Ratio 15 (3): 276–292.

Prior, Arthur. N. 1959. Thank Goodness That’s Over. Philosophy. 34(128): 12−17.

Sullivan, Meghan. forth. Time Biases: A Theory of Rational Planning and Personal Persistence. New York: Oxford University Press.

Van Boven, Leaf & Ashworth, Laurence. 2007. Looking Forward, Looking Back: Anticipation Is More Evocative Than Retrospection. Journal of Experimental Psychology. 136(2): 289–300.

What hand gestures tell us about the evolution of language

Suzanne Aussems – Post-Doctoral Fellow/Early Career Fellow, Language & Learning Group, Department of Psychology, University of Warwick

Imagine that you are visiting a food market abroad and you want to buy a slice of cake. You know how to say “hello” in the native language, but otherwise your knowledge of the language is limited. When it is your turn to order, you greet the vendor and point at the cake of your choice. The vendor then places his knife on the cake and looks at you to see if you approve of the size of the slice. You quickly shake both of your hands and indicate that you would like a smaller width for the slice using your thumb and index finger. The vendor then cuts a smaller piece for you and you happily pay for your cake. In this example, you achieved successful communication with the help of three gestures: a pointing gesture, a conventional gesture, and an iconic gesture.

As humans, we are the only species that engage in the communication of complex and abstract ideas. This abstractness is even present in a seemingly simple example such as indicating the size of a slice of cake you desire. After all, size concepts such as ‘small’ and ‘large’ are learnt during development. What makes this sort of communication possible are the language and gestures that we have at our disposal. How is it that we came to develop language when other animals did not, and what is the role of gesture in this? In this blogpost, I introduce one historically dominant theory about the origins of human language – the gesture-primacy hypothesis (see Hewes, 1999 for an historic overview).

According to the gesture-primacy hypothesis, humans first communicated in a symbolic way using gesture (e.g. movement of the hands and body to express meaning). Symbolic gestures are, for example, pantomimes that signify actions (e.g., shooting an arrow) or emblems (e.g., raising an index finger to your lips to indicate “be quiet”) that facilitate social interactions (McNeil, 1992; 2000). The gesture-primacy hypothesis suggests that spoken language emerged through adaptation of gestural communication (Corballis, 2002, Hewes, 1999). Central to this view is the idea that gesture and speech emerged sequentially.

Much of the evidence in favour of the gesture-primacy hypothesis comes from studies on nonhuman primates and great apes. Within each monkey or ape species, individuals seem to have the same basic vocal repertoire. For instance, individuals raised in isolation and individuals raised by another species still produce calls that are typical for their own species, but not calls that are typical for the foster species (Tomasello, 2008, p. 16). This suggests that these vocal calls are not learned, but are innate in nonhuman primates and great apes. Researchers believe that controlled, complex verbal communication (such as that found in humans) could not have evolved from these limited innate communicative repertoires (Kendon, 2017). This line of thinking is partly confirmed by failed attempts to teach apes how to speak, and failed attempts to teach them to produce their own calls on command (Tomasello, 2008, p. 17).

However, the repertoire of ape gestures seems to vary much more per individual than the vocal repertoire (Pollick & de Waal, 2007), and researchers have succeeded in teaching chimpanzees manual actions with the help of symbolic gestures that were derived from American Sign Language (Gardner & Gardner, 1969). Moreover, bonobos have been observed to use gestures to communicate more flexibly than they can use calls (Pollick & de Waal, 2007). The degree of flexibility in the production and understanding of gestures, especially in great apes, makes this communicative tool seem a more plausible medium through which language could have first emerged than vocalisation.

In this regard, it is notable that great apes that have been raised by humans point at food, objects, or toys they desire. For example, some human-raised apes point to a locked door when they want access to what’s behind it, so that the human will open it for them (Tomasello, 2008). It is thus clear that human-raised apes understand that humans can be led to act in beneficial ways via attention-directing communicative gestures. Admittedly, there does seem to be an important type of pointing that apes seem incapable of; namely, declarative pointing (i.e., pointing for the sake of sharing attention, rather than merely directing attention) (Kendon, 2017). Nonetheless, gesture seems to be a flexible and effective communicative medium that is available to non-human primates. This fact, and the fact that vocalisations seem to be relatively inflexible in these species, play a significant role in making the gesture-primacy hypothesis a compelling theory for the origins of human language.

What about human evidence that might support the gesture-primacy hypothesis? Studies on the emergence of speech and gesture in human infants show that babies produce pointing gestures before they produce their first words (Butterworth, 2003). Shortly after their first birthday, when most children have already started to produce some words, they produce combinations of pointing gestures (point at bird) and one-word utterances (“eat”). These gesture and speech combinations occur roughly three months before producing two-word utterances (“bird eats”). From an ontogenetic standpoint, then, referential behaviour appears in pointing gestures before it shows in speech. Many researchers therefore consider gesture to pave the way for early language development in babies (Butterworth, 2003; Iverson & Goldin-Meadow, 2005).

Further evidence concerns the spontaneous emergence of sign language in deaf communities (Senghas, Kita, & Özyürek, 2004). When sign language is passed on to new generations, children use richer and more complex structures than adults from the previous generation, and so they build upon the existing sign language. This phenomenon has led some researchers to believe that the development of sign language over generations could be used as a model for the evolution of human language more generally (Senghas, Kita, & Özyürek, 2004). The fact that deaf communities spontaneously develop fully functional languages using their hands, face, and body, further supports the gesture-primacy hypothesis.

Converging evidence also comes from the field of neuroscience. Xu and colleagues (2009) used functional MRI to investigate whether symbolic gesture and spoken language are processed by the same system in the human brain. They showed participants meaningful gestures, and the spoken language equivalent of these gestures. The same specific areas in the left side of the brain lit up for mapping symbolic gestures and spoken words onto common, corresponding conceptual representations. Their findings suggest that the core of the brain’s language system is not exclusively used for language processing, but functions as a modality-independent semiotic system that plays a broader role in human communication, linking meaning with symbols whether these are spoken words or symbolic gestures.

In this post, I have discussed compelling evidence in support of the gesture-primacy hypothesis. An intriguing question that remains unanswered is why our closest evolutionary relatives, chimpanzees and bonobos, can flexibly use gesture, but not speech, for communication. Further comparative studies could shed light on the evolutionary history of the relation between gesture and speech. One thing is certain: gesture plays an important communicative role in our everyday lives, and further studying the phylogeny and ontogeny of gesture is important for understanding how human language emerged. And it may also come in handy when ordering some cake on your next holiday!

 

REFERENCES

Butterworth, G. (2003). Pointing is the royal road to language for babies. In S. Kita (Ed.) Pointing: Where Language, Culture, and Cognition Meet (pp. 9-34). Mahwah, NJ: Lawrence Erlbaum Associates.

Corballis, M. C. (2002). From hand to mouth: The origins of language. Princeton, NJ: Princeton University Press.

Gardner, R. A., & Gardner, B. (1969). Teaching sign language to a chimpanzee. Science, 165, 664–672.

Hewes, G. (1999). A history of the study of language origins and the gestural primacy hypothesis. In: A. Lock, & C.R. Peters (Eds.), Handbook of human symbolic evolution (pp. 571-595). Oxford, UK: Oxford University Press, Clarendon Press.

Iverson, J. M., & Goldin-Meadow, S. (2005). Gesture paves the way for language development. Psychological Science, 16(5), 367-371. Doi: 10.1111/j.0956-7976.2005.01542.x

Kendon, A. (2017). Reflections on the “gesture-first” hypothesis of language origins. Psychonomic Bulletin & Review, 24(1), 163-170. Doi: 10.3758/s13423-016-1117-3

McNeill, D. (1992). Hand and mind. Chicago, IL: Chicago University Press.

McNeill, D. (Ed.). (2000). Language and gesture. Cambridge, UK: Cambridge University Press.

Pollick, A., & de Waal, F. (2007). Ape gestures and language evolution. PNAS, 104(19), 8184-8189. Doi: 10.1073/pnas.0702624104

Senghas, A., Kita, S., & Özyürek, A. (2004). Children creating core properties of language: evidence from an emerging sign language in Nicaragua. Science, 17, 305(5691), 1779-82. Doi: 10.1126/science.1100199

Tomasello, M. (2008). The origins of human communication. Cambridge, MA: MIT Press.

Xu, J., Gannon, P. J., Emmorey, K., Smith, J. F., & Braun, A. R. (2009). Symbolic gestures and spoken language are processed by a common neural system. PNAS, 106(49), 20664–20669. Doi: 10.1073/pnas.0909197106