Babies know who’s boss, whose boss, and who knows what else.

forthcoming paper (grateful nod to ICCI) in PNAS from Olivier Mascaro and Gergely Csibra presents a series of experiments investigating the representation of social dominance relations in human infants, and it’s excellent news: we’re special.

Social dominance can be inferred in a couple of ways. Causal cues such as age, physical aggression and size can tell us about the dominance status of an individual quite intuitively, so we can make a sensible decision about whether or not we get into a scrap with them. Another way we can establish this is to look for direct realisations of dominance, such as who gets the banana if two hungry chimps both want it; chances are, little Pan Pipsqueak isn’t going to get a look in. In order to be useful, we also have to use this information to expect certain things from the individuals around us, so those representations have some property of stability across time that allows us to have those expectations. The question being explored in this paper is whether the representations we have are about the relationship between the two agents who want the banana, or the individual properties each of them has.

In a series of experiments using preferential looking time as a dependent measure, human infants (9 and 12 month olds) were exposed to videos of geometric figures exhibiting similar goal-directed behaviour. Then they would watch, say, a dominant triangle picking up the last figurative banana when the nondominant pentagon also wanted it. For expository purposes and posterity’s sake, I have constructed an artist’s impression of a dominant triangle and a subordinate pentagon in MSPaint (below, right):

A dominant triangle and subordinate pentagon (artist’s impression).

I’m not just showing off my extraordinary artistic talent here; the good thing about these agents is that there are none of the cues like size or aggression that can give rise to the assignment of individual dominance properties. The task also doesn’t indicate anything similar; it’s just about who gets the desired object when there’s only one left. In other words, the goal-directed actions of two agents are in opposition. After seeing a triangle beat a pentagon to an object of ‘banana’ status, 12 month olds looked for longer when they were then presented with an incongruent trial where the pentagon gained over the triangle. 9 month olds (understandably?) couldn’t care less. So, on the basis of this social interaction alone, the 12 month olds were able to notice when something unexpected happened.

To rule out the possibility that this was just the result of some simple heuristic such as “when triangle and pentagon are present, triangle gets the object” and make sure the infants really were assigning some dominance, another experiment (with 12 and 15 month olds) showed the same test video of the two agents collecting little objects. This time, however, the preceding video was of the triangle dominating a little walled-in space that the pentagon also wanted to inhabit. The 12 month olds had no idea what was up, but the 15 month olds generalised from the first “get out of my room” interaction to the “I get the last banana” interaction. So, 15 month olds can extract, just from watching a social interaction, the dominance status of agents and can generalise that information to novel situations. So if a 15 month old watches you lose your favourite seat in front of the TV, they’ll also expect you to miss out on the last slice of pizza, because you’re a loser.

What we still don’t know is whether they think your belly is inherently yellow, or if you’re just a pushover when interacting with a particular person. Is it the relationship between the triangle and pentagon that the babies are tracking, or do they just give each agent some sort of dominance score? This was addressed in experiment 4, where infants were presented with two interactions: one between A and B, where A wins, and then another between B and C, where B wins. If the babies are assigning an individual value to each agent, they should have some sort of linear, transitive representation of dominance like A > B > C. If they’re then presented with a novel interaction between A and C, they would have the expectation that A will beat C. So if they stare in surprise at a trial where C wins, we know it’s violated that kind of expectation, and that they’re representing this stuff linearly – I.E. each agent has a dominance value. In contrast, if the infant is tracking the relations between agents, they can’t really have an expectation of what will happen when A and C both want a banana, because they’ve never seen C before. The results find that the infants look preferentially when they get an incongruent trial using agent pairs they have seen before – as we’d expect from the previous experiment. When they’re presented with a new “I get the last banana” interaction between A and C, however, there’s nothing startling about it when C wins – which means their expectations are not based on something like A > B > C.

The only tiny little harrumph I have about this result is that all it does is falsify the linear representation account. Though I think their account is absolutely right, it’d be nice to see something more predictive come out of the relation-representation hypothesis that is a little more falsifiable. But this result is pretty huge, and stands in contrast with what we know about social cognition in other animals like baboons (Cheney et al, 1995; Bergman et al, 2003), lemurs (Maclean et al., 2008) and even pigeons (Lazareva & Wasserman, 2012), who seem to employ this sort of hierarchical, transitive inference when presented with novel interactions. It may also muddy the waters a little when we want to make the appealing claim that, since language surely emerged in order to enable communication as we navigated a social environment, hierarchical social cognition gives rise to the processing of languagey things like hierarchical syntax or our semantic representation (Hamilton, 2005), which can be characterised as hierarchical (e.g. hyperonym > hyponym). If we consider the nature of the human social environment, though, it should seem more intuitive that something more reliable than simple transitive inference is necessary in order to successfully navigate through our interactions. Due to our prolific production of (and reliance on) culture, humans have a much more diverse range of social currencies, which correspond to values for things like money, intelligence, blackmail information, who your friends are, ad infinitum. That means it’s pretty reasonable that our social cognition needs new strategies in order to get by; we have a little more to consider than just who’s big and angry enough to get all the bananas.


Bergman, T., Beehner, J., Cheney, D. & Seyfarth, R. (2003) “Hierarchical Classification by Rank and Kinship in Baboons” Science 14(302), 1234-1236.

Cheney, D., Seyfarth, R. & Silk, J. (1995) “The response of female baboons (Papio cynocephalus ursinus) to anomalous social interactions: evidence for causal reasoning?” Journal of Comparative Psychology 109(2), 134-141.

Hamilton, D.L. (2005) Social Cognition: Key Readings (p. 104) Psychology Press

Lazareva, O. & Wasserman, E. (2012) “Transitive inference in pigeons: measuring the associative values of stimulus B and D” Behavioural Process 89(3), 244-255.

Maclean, E., Merritt, D. & Brannon, E.M. (2008) “Social complexity predicts transitive reasoning in prosimian primates” Animal Behaviour 76(2), 479-486.

Mascaro, O. & Csibra, G. (forthcoming) “Representation of stable dominance relations by human infants” Proceedings of the National Academy of Sciences


Animal Cognition & Consciousness (II): Metacognition & Mentalizing

As I wrote in my last post, three kinds of behaviours are most often discussed in debates about animal consciousness and cognition:

“1. Mirror self-recognition

2. Tests of metacognition;

3. Metacognition of others’ mental states” (Gómez 2009: 45)

After having discussed the first capacitiy in my previous post, I will discuss the latter two in this post, starting with metacognition, that is being aware of one’s own knowledge states, and then turn to being aware of other’s mental states.


Being aware of one’s own mental states, i.e., reflective consciousness, surely seems to be one of the most crucial components of self-awareness. In one paradigm used to test for metacognitive awareness, monkeys were trained to select, out of a number of two or more images, the one that is identical to an image they have been shown earlier. As is to expected, the monkeys’ performance progressively deteriorated the longer the delay was between the sample image and the selection task.


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Animal Cognition & Consciousness (I): Mirror Self-Recognition

Darwin made a mistake. At least that is what Derek Penn and his colleagues (2008) claim in a recent and controversial paper in Behavioral and Brain Sciences. Darwin (1871) famously argued that the difference between humans and animals was “one of degree, not of kind.”

This, according to Penn et al. is of course true from an evolutionary perspective, but in their view,

“the profound biological continuity between human and nonhuman animals masks an equally profound discontinuity between human and nonhuman minds” (Penn et al. 2008: 109).

They hold that humans are not simply smarter, but human cognition differs fundamentally and qualitatively from that of other animals.

One pervasive proposal is that we do not simply possess a unique set of cognitive capacities, but that it might be consciousness itself that is uniquely human as well, a view that goes back at least to Descartes (Burkhardt & Bekoff 2009: 41). However, there are also many scholars and researchers who agree that there is evidence for higher-order cognition in nonhuman animals ( ‘animals’ after this) and that they might possess at least some degree of consciousness (Burkhard & Bekoff 2009: 40f.).

In this and my next post, I will write about three kinds of phenomena that are most often discussed in debates on whether animals have some form of higher-order cognition and consciousness or not: self-awareness, awareness of one’s own cognitive states, and awareness of others’ cognitive states and intentions.

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The Gestural Repertoire of the Wild Chimpanzee

In the past many studies have been done on the linguistic abilities of trained apes using artifical languages, but what about in the wild?

Catherine Hobaiter and Richard W. Byrne at the University of St. Andrews have carried out a new study looking at the intentional gestures of chimpanzees in the wild.

Whilst it is generall agreed that gestural communication in great apes as seen in the wild is intentional and elaborate and flexible the authors outline that there is still a lot of controversy with regards to interpretation of the system and how the apes acquire it. These questions are hard to untangle when studied in the captive settings of a zoo.

The study presents a systematic analysis of the gestures made by a population of chimpanzees in the wild. 4,397 cases of intentional gesture were recorded in Budongo, Uganda.

These recordings were used to identify 66 gesture types. These gestures were seen to differ between individuals and also between age classes. Regardless of these differences no gesture was used only by one individual. I worried when I first read this as sometime studies identify intentional gestures by using the criteria that the gestures were used in the same context a certain number of times, however, within this study the criteria for intention gesture was as follows:

Audience checking: The signaller shows signs of beingaware of the potential recipients and their state ofattention, e.g. turning to look at the recipient beforegesturing.

Response waiting: The signaler pauses at the end of thecommunication and maintains some visual contact.

Persistence: The production of further gestures, afterresponse waiting and in the absence of a response that in other cases is taken as satisfactory. (In certain circumstances, such persistence might be impossible, for example where an adult carries an infant away; these cases are marked as unable to persist, rather than nopersistence.)

The authors argue that these gestures are not acquired by ‘ontogenetic ritualization’, which is when actions which are performed to reach some goal become ritualised to the point that they can be anticipated from an intial gesture sequence. The authors carried out detailed analyses of two gestures to show that the action elements which the gestures were made up from did not match those of the original actions.

This lack of ontogenetic ritualisation may be down to these gestures being species-typical, or typical across all the great apes. Comparisons made with the recorded gestured of gorillas and orangutans show that chimpanzee overlap with at least 24 gestures which are recorded in all three species. Dr Hobaiter is cited as saying on the BBC story that:

“the gestures that apes use (and maybe some human gestures too) are derived from ancient shared ancestry of all the great ape species alive today.”

The gestures were also able to be used flexibly across contexts and were able to adjust to the audience, for example the chimps were shown giving silent gestures when their audience was attentive and used contact in their gestures when the audience was inattentive.

The paper includes extensive analysis of repertoire size across age groups, contexts each gesture type was used in as well as things like hand position and shape during gestures.

This is the first study of its type using a wild population of chimpanzees. It shows highly intentional use of a species-typical repertoire which seems surprising and certainly contributes evidence relating to the evolution of intentional communication.


Catherine Hobaiter and Richard W. Byrne (2011) The gestural repertoire of the wild chimpanzee. ANIMAL COGNITION. DOI: 10.1007/s10071-011-0409-2


The adaptive value of age, co-operation (and secret signals)

More elephant based news!

A new study from the Proceedings of the Royal Society B, published today, has found that elephants pay attention to the oldest female elephant in their group when a predator is approaching.

The research, carried out in Kenya, used recordings of roars from both male and female lions and monitored the reactions of groups of African Elephants. It has been known for a long time that elephants social groups are formed around a matriarchy. The experiment found that groups of elephants with matriarchs quickly organised themselves into defensive bunch formations after appearing to stop and pay attention to their female leader. These groups were also much more likely to approach the loud speaker producing the roar in an aggressive manner.

Male lions present a greater threat to groups of elephants as they are much more likely to attack elephants when alone and are usually much more successful than females who will only attack when part of a group. The elephants showed an ability to differentiate between male and female lions. The study also showed that matriarchs who were much older were much more likely to react in the appropriate way to roars made by male lions which is thought to be the result of experience.

The signals which allow the Matriarch to elicit this co-ordination among her group are still largely unknown due to the lack of loud vocalisations and Karen McComb and Graeme Shannon, who lead the initial study, are now looking into finding quieter, less obvious vocalisations and posture cues.

The study provides the first empirical evidence that within a social group, individuals may gain benefits from paying attention to an older leader because of their abilities in making decisions when under threat. This generates insights into selection for longevity in cognitively advanced social mammals.

Imitation and Social Cognition in Humans and Chimpanzees (II): Rational Imitation in Human Infants and Human-Raised Chimps

In my last post I wrote about two experiments on imitation in young children and chimpanzees by Lyons et al. (2005) and Horner & Whiten (2005).  Their results suggested that young children tend to copy both the ‘necessary’ and the ‘unnecessary’ parts of a demonstrator’s action who shows them how to get a reward out of a puzzle box, whereas chimps only copy the ones necessary to get the reward.

ResearchBlogging.orgOne important question raised by these experiments was whether these results can only be applied to wild chimpanzees or whether they also hold for enculturated, human-raised chimps. This is an important question because it is possible that chimpanzees raised in these kinds of richly interactive contexts show more sensitivity to human intentionality.

Buttelman et al. (2007) tested just that. They used the “rational imitation” paradigm, which features two conditions

a) the subjects are shown an action in which the specific manner of the action is not purposive and intentional but results from the demonstrator being occupied with something else. For example, he may be carrying something so that he has to use his foot to turn on a light (often called the Hands Occupied Condition).

b) the subjects are shown an action in which the demonstrator chooses a specific manner of doing something on purpose. For example he may have his hands free but still choosto turn on the light with his foot (Hands Free Condition).

taken from Call & Tomasello 2008

Continue reading “Imitation and Social Cognition in Humans and Chimpanzees (II): Rational Imitation in Human Infants and Human-Raised Chimps”