The cognitive requirements of cumulative culture: experiments with typically developing and autistic people

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Human culture accumulates and increases in complexity over generations, building on what came before. This phenomenon, termed cumulative cultural evolution, generates ever-more efficient tools and technologies and has helped humans to spread across the globe, but its causes remain mysterious. Many animals have simple forms of culture such as tools, foraging methods and social rituals that spread through groups by learning, but the cumulative nature of human culture seems to be unique in the animal kingdom. We will examine the cognitive processes that make human culture possible using experiments with autistic and typically developing (TD) people.The most widely accepted explanation for cumulative cultural evolution is that it relies on a set of three cognitive processes that are rare or absent in other animals but allow humans to learn from each other with great accuracy and so build upon cultural knowledge. First, imitation: the ability to copy the others' precise actions. Second, teaching, whereby knowledgeable individuals actively help others learn. This is thought by psychologists to require Theory of Mind (ToM), the ability to reason about what others know and so correct their ignorance. Third, social attention: engaging others to work together to achieve joint goals. To date, firm evidence for this hypothesis is lacking and different studies have produced contradictory results. As deficits in imitation, ToM and social attention are among the key features of autism, experiments comparing autistic and TD people can help determine whether these processes are needed for cultural information to be passed on and accumulate.We will use experiments to test whether imitation, teaching and social attention are required for cultural improvements in tools of differing levels of complexity. In one experiment, we will set up "transmission chains" of TD people where the first person makes a tool from everyday materials without any guidance, the second person can learn from the first, and so on. In a third of the chains participants will be able to watch and imitate the previous person. In another third, each participant will remain as a teacher to help the next person and in the remaining chains participants will simply see the final product made by the previous person. We predict that simple tools will become more efficient across all the chains, but for more complex tools imitation and teaching will be necessary to generate improvements. A second experiment will use groups of autistic and TD children working in pairs to make tools over eight rounds, with one member of the pair being replaced by a new child after each round. We expect the autistic children to show less social attention and teaching, so compared to the TD children their tools should show little improvement over the rounds.Our other experiments will examine the common but untested assumption that human teaching requires ToM. Instead of reasoning about pupils' knowledge, people may also use visible indicators of pupils' abilities to deliver effective lessons. To test this, we will ask TD and autistic children to teach other children simple games and tool-using tasks. By varying the age of pupils and using "stooge" pupils that make deliberate mistakes we will find out whether autistic children, despite their ToM impairments, can deliver effective lessons targeted to the age and competence of their pupils. Finally, we will examine a specialised form of human teaching, motherese: the simplified and exaggerated baby-talk used by parents across cultures that appears to help babies learn to speak. We propose that motherese may not require ToM but is in fact an automatic human response to baby-like features. This may explain why people speak in a similar way to babies and cute pets. If we are correct, then autistic children, despite their ToM deficits, will show similar patterns to TD children in experiments where they are asked to talk to a dog, a baby or an adult