MLU: You note that the Pirahã have difficulty perceiving images in photographs. Having been an artist all of my life, I found this very interesting for what it might tell us about the human mind. I've taught hundreds of students to draw and paint over the years, and I found that they do much better if they are taught to not think of their subject as a thing they recognize, but rather as an abstract pattern. In copying a face from a photograph, for instance, they do better when drawing the photo upside down--because it forces them to look at shape-relationships rather than what they think they see.
This tells me that much of what we think of as comprising reality are actually assumptions which we carry around in our heads. So when you noted that the Pirahã have difficulty perceiving images in photographs, it made perfect sense: two-dimensional representations of reality are simply not a part of their world-view. I could be wrong, but this seems like a great example of how their culture has actually modified the way they think, and the way they think, of course, is reflected by their language.What's your take on why the Pirahã don't see photographic images the way we do?DE: The Pirahãs' lack of ability to recognize pictures is especially acute in those with the least contact with the outside world. Some psychologists have wondered over the years whether perception of pictures and other two-dimensional representations is innate or learned. Our initial experiments, described in my book, seem to show that such perception is learned, not innate. In this particular case, however, I would not appeal to a cultural taboo or value associated with the phenomenon. It is to my mind simply a lack of experience. If perception of two-dimensional representations is learned, then the explanation is simply that they haven't had a chance to learn this skill. That they can learn it is shown by the greater ability of those who have traveled to cities more often, where billboards, signs, and other two-dimensional representations are everywhere.
MLU: You found out something amazing about the Pirahã and numbers. What was this discovery, and what did it tell you about human cognition?
DE: When I first went to work on the Pirahã language, I looked at what previous folks there had written. I had been preceded by two other missionaries, Arlo Heinrichs, who was the first missionary or linguist to work with the Pirahãs (he had had some linguistic training), from 1959-1967, and Steven Sheldon, who had an MA in linguistics and had worked with the Pirahãs from 1967-1976. Both Steve and Arlo had talked about the Pirahãs having the numbers 'one', 'two', and 'many', which was not an uncommon system. And my initial experiences seemed to confirm this. They almost always used the word 'hói' for one object, 'hoí' for two objects, and 'báagiso' for three or more objects. I didn't really think much about it. I was told what the words meant, they matched my initial experience, they were not uncommon, and I had a lot more to do than work on numbers. However, over the years, I realized that 'hoí' could be used on more than two objects, overlapping frequently with what I thought 'báagiso' mean, i.e. 'many'. I then began to notice that the words I thought meant 'one' and 'two' could be reversed. When confronted with two teeny fish and one large fish, many Pirahã would refer to the two teeny fish as 'hói' and the one large fish as 'hoí'. I got the idea that these Pirahã words didn't refer to numbers so much as relative volumes/quantities. I noticed too that the Pirahãs never count, never use their fingers to 'tally' objects, and seemed to lack any notion of keeping track of exact quantities. I was by then teaching at the University of Pittsburgh and I mentioned my hypothesis that Pirahã lacked counting (though I still said that they had numbers 'one', 'two', and 'many', but without much precision, i.e. with polysemy in each term) to a colleague in Psychology, Peter Gordon (now at Columbia University). Peter went with me three years in a row to the Pirahãs and spent a few months total studying their counting. He published a paper in Science in 2004 based on this research that he had conducted more than a decade previously. It was a huge sensation. Ironically, at the same time, and unaware of his ms. for Science, I was doing my own thinking about Pirahã numerals and counting because I had been invited to talk at a conference on Numerals at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. I concluded, after spending a lot of time reviewing all my data, that the Pirahãs in fact did not have any numbers at all. This created quite a stir at the Leipzig conference and there was some skepticism (quite naturally), since no other system like this had been discovered (though I suspect now that other so-called 'one', 'two', 'many' systems will turn out to lack numbers too). Both Peter and I agreed that the Pirahãs lacked counting, but he continued to claim, ironically based mainly on what I had told him at the time he did his Pirahã research, that they had numbers.
This interested some folks at MIT's Department of Brain and Cognitive Sciences so they contacted me about the possibility of going to Brazil, at their own expense, on my next trip down, to conduct some experiments (the main researcher was Prof. Ted Gibson, along with two of his PhD students, Evelina Fedorenko and Mike Frank, who is now Assistant Professor of Psychology at Stanford). The results of the experiments we did together, published in the journal Cognition, established fairly clearly that Pirahã lacked numbers altogether (this paper was chosen by Discovery Magazine as one of the 100 most important science stories of 2008). By then, I had incorporated the lack of numbers into my discussion of other Pirahã linguistic characteristics that I have attempted to account for on cultural grounds. But whatever the explanation, the lack of numbers was a significant discovery because it showed, contra a great many claims by psychologists, linguists, and others, that numbers were innate. They are not.