Culture has rightfully become an important topic in human evolutionary biology in the last few decades. Our ability to rapidly adapt to new ecological and social environments is due in large part to our impressive ability to acquire ideas, technologies, and behaviors from others and, over time, to incrementally improve upon them. Other species learn behaviors and technologies from others, but they do not do so at nearly the same frequency and scope, nor with the same fidelity. We truly have exploited the ‘cultural niche’ (a term used by Boyd, Richerson, and Henrich , and stolen by me to name this website). That second inheritance system—a cultural inheritance system in addition to a genetic inheritance system, which is more than just increased intelligence—has a colossal impact on our phenotypes, and has likely been a powerful force in human evolution for long enough that to marginalize it would be unwise.
Most researchers who study culture and human evolution would agree that the systems that make cultural learning possible, such as social learning, teaching, imitation, and theory of mind, are adaptations that arose from genetic evolution. Since the cognitive mechanisms for abilities like sight, memory, and emotions are genetically inherited, why shouldn’t cultural learning mechanisms be as well? In a new special issue of the Philosophical Transactions of the Royal Society B about “New Thinking” in human cognitive evolution (which I recently wrote about here), Cecilia Heyes argues that even the mechanisms that allow for cultural learning are learned culturally.
To step back, this may sound like an odd claim. Cultural learning to culturally learn sounds paradoxical, but all she argues is that the same processes used to facilitate cultural learning are acquired non-genetically during development, and non-genetic inheritance is often used as a working definition for culture. She proposes that through our early social interactions, the cognitive systems that we use for asocial learning, or individual learning, are tweaked in different ways that allow the input and processing of social information. This will make more sense when I talk about social learning, but Heyes first provides evidence that cultural learning can be culturally inherited by talking about reading.
Reading is a powerful cultural inheritance system which allows readers to access knowledge from nearly any time and place—provided that it’s in a language that the reader can understand—and to contribute one’s own knowledge to future generations. However, written language is only a few thousand years old and nearly everyone until recent times was illiterate. No one would argue that the cognitive mechanisms that allow people to process written language were the products of genetic selection. Nevertheless, learning to read introduces several new cognitive processes and redefines how many older processes function. It creates a new input channel to the mechanisms that process language, one which was not originally there and was not put in place by natural selection.
When literate individuals are presented with written language inside of an fMRI scanner, there are several brain regions, that reliably activate to higher levels than when they are presented to illiterate individuals (Dehaene et al. ). These brain regions exist in both groups, of course, but among literates, those regions’ functions have been radically altered. One of these areas, the left posterior midfusiform gyrus, appears to activate specifically to written language in literate people, as if that had been the purpose for which it was there at all. Though controversial, this area has been referred to in the literature as the visual word form area. Reading also alters lower level perceptual processes. Literate people hear spoken language differently as being divided into different sets of smaller meaningful components which would not be important for illiterate people (sentences, paragraphs, compound words). Literate people also have increased activation in the visual areas of the brain when hearing spoken language, as if they were visualizing the words that they hear.
If we were not already sure that reading was a culturally acquired ability, this cognitive and neurological pattern would probably fool us into thinking that the ability was innate and installed by natural selection. However, since we know that it wasn’t, which other cognitive abilities may be culturally acquired that we have been fooled into thinking are innate, Heyes asks. Whereas most in the field of comparative psychology would argue that the abilities for cultural learning—broadly, abilities like social learning, imitation, teaching, etc.—are genetic adaptations, she argues that there is not much evidence to support this, and in fact, some evidence that suggests the contrary. In her article, she argues that two of these abilities—social learning and imitation—are culturally learned. Out of interest for time, I’ll only talk about social learning.
Social learning is a special class of learning strategies in which individuals acquire information or behaviors from the actions or experiences of other individuals—as long as that information wasn’t shaped by the other individual for it to be learned by another. Learning what to eat by watching what someone else eats, or learning to make a tool by watching how someone else does, or learning that bees are dangerous by watching someone get stung are all examples of social learning. However, if the other individual tells you or purposefully shows you what you should eat, how to make a tool, or to avoid bees, then it would be an example of either teaching or signaling. Heyes also points out that studying social learning is beneficial because it’s found in many species and we can use a comparative approach.
Heyes argues instead, however, that there is little evidence that social learning was a distinct adaptation from other forms. She denies, against the common thought in her field, that social learning involves any of its own processes. Instead, she argues that the learning mechanisms that enable social learning are the same as those used in individual learning. These mechanisms are the associative learning mechanisms that form links between two stimuli in the environment, for example, or between a stimuli and a response. The difference is that the input mechanisms that feed into those learning mechanisms have been biased to process information from social sources rather than only from the environment.
She offers five lines of evidence for this assertion which are only briefly treated in this article but are covered at greater length here. First, social learning and asocial (associative) learning are positively correlated, meaning that animals that perform well on asocial learning tasks are more likely to perform well at social learning tasks as well. Second, solitary animals can be good as social learning as well. If social learning were an adaptation to life in a social group, one would not expect non-social animals to display social learning at all. However, many solitary animals like the common octopus and the red-footed tortoise show that the relation is not absolute.
Third, she points out that the different types of social learning are very similar to the different types of asocial, or individual, learning. Stimulus enhancement and observational conditioning are two different kinds of social learning that differ in the number of stimuli that are processed. When the actions of some other individual make something in the environment more salient and likely to be attended to, then it is called stimulus enhancement, whereas when that other individual’s actions allow the relationship between two stimuli to be learned, then it is observational conditioning. These two types of learning have asocial learning counterparts in single-stimulus learning, such as habituation and sensitization, and stimulus-stimulus learning, such as Pavlovian conditioning. Fourth, these types of social and asocial learning are found across the animal kingdom and they work in the same ways across species. And lastly, social learning abilities still display the same biases and side-effects of their asocial learning counterparts such as overshadowing and blocking.
According to Heyes, this is good evidence to suggest that social learning and asocial learning are based on the same core associative learning faculties. There is no reason to think that they are completely distinct systems. It would be inefficient if they were, and evolution tends to select against inefficiency when possible. Instead, they differ only by how they are inputted into that core associative system. Heyes argues that the input systems to the core learning system are adjusted to allow social inputs. There is not enough evidence so far to make a strong claim about whether that adjustment is an evolved adaptation or something that occurs during development. However, she cites two studies that point towards a developmental origin in humans.
The first study by Behrens et al.(2008) had subjects choose between two options on a computer screen that would give different point values to the player. Each choice had a number value on the computer screen that would sometimes reflect which choice would give the higher point value. At other times, that number would be misleading. The subjects would also receive advice from an unseen individual on which would have the higher point payoff. That advice would sometimes be helpful or, at other times, misleading. They found that people quickly learn to adjust their reliance on the social and asocial sources of advice when choosing between the two options. Brain scans during the trials also showed varying activations in areas known to be associated with social advice (the medial prefrontal cortex) and with processing number value (the ventral striatum) which reflected how much value the subjects were giving to each source. This study shows that associative learning affected whether the social and asocial input systems would be preferred when choosing between the two options when each could be misleading. This suggests further that the input channels share the same processing hub, consistent with Heyes’ argument.
Second, Jack et al. (2009) used eye movement tracking to show that there are differences in how Westerners and East Asians look at faces to identify emotions. Westerners tended to divide their time between looking at the eyes and the mouth, while East Asians tended to devote most time looking at the eyes. This led to differences in how well each group performed at identifying different emotions. East Asians were less able to correctly identify fear and disgust than Westerners, since they display similar eye movements but different mouth movements. Heyes hypothesizes that if Westerners are better at identifying fear and disgust, they may be better at learning about disgusting or dangerous things by observational conditioning than East Asians. This would be due only to their cultural background and not to any genetic differences. However, that study would need to be done for it is considered as strong evidence.
Although the evidence is still limited, Heyes makes a strong case for future research into this question. In her article, she goes on to show why she thinks that imitation, the form of social learning that is most essential for cumulative cultural inheritance to develop, is also a culturally derived ability that develops by the creation of what are known as “mirror neurons” during development.
This work ties into the “New Thinking” (NT) that is the focus of the special issue in which Heyes’ paper was published. The NT proposes that the mind is not made up innately of modules, as modern evolutionary psychology assumes, but that the mind has powerful domain-general mechanisms that create those modules during development, as was the case in reading. The engines behind that process are the associative learning abilities presented above. These processes, she argues, produce all of the learning mechanisms that constitute cultural learning through modular development using associative learning. Much more research will have to be done to find out if this argument holds up, but if true, it will fundamentally change how we think about the evolution of those abilities that make us unique and able to adapt to so many different habitats around the world.
Video Presentation by Cecilia Heyes here.