Language of thought theories rely on the belief that mental representation has linguistic structure. Thoughts are "sentences in the head" and so take place within a mental language. Two theories work in support of the language of thought theory. Causal syntactic theory of mental practices hypothesizes that mental processes are causal processes defined over the syntax of mental representations. Representational theory of mind hypothesizes that propositional attitudes are relations between subjects and mental representations. In tandem, these theories explain how the brain can produce rational thought and behavior. All three of those theories were inspired by the development of modern logical inference. They were also inspired by Alan Turing's work on causal processes that require formal procedures within physical machines.3
The language of thought hypothesis hinges on the belief that the mind works like a computer, always in computational processes. The theory believes that mental representation has both a combinatorial syntax and compositional semantics. The claim is that mental representations possess combinatorial syntax and compositional semantic—that is, mental representations are sentences in a mental language. Turing's work on physical machines implementation of causal processes that require formal procedures was modeled after these beliefs.4
Another prominent linguist, Steven Pinker, developed the idea of a mental language in his book The Language Instinct (1994). Pinker refers to the mental language as "mentalese". In the glossary of his book, Pinker defines mentalese as a hypothetical language that is used specifically for thought. The hypothetical language houses mental representations of concepts such as the meaning of words and sentences.5
Different cultures use numbers in different ways. The Munduruku language, for example, has number words only up to five. In addition, it refers to the number 5 as "a hand" and the number 10 as "two hands". Numbers above 10 are usually referred to as "many".
Perhaps the counting system that is the most different from that of modern Western civilisation is the "one-two-many" system used in the Pirahã language in which quantities larger than two are referred to simply as "many". In larger quantities, "one" can also mean a small amount and "many" a larger amount. Research was conducted with the Pirahã by using various matching tasks. The non-linguistic tasks were analyzed to see if their counting system or, more importantly, their language affected their cognitive abilities. The results showed that they perform quite differently from, for example, an English-speaking person who has a language with words for numbers more than two. For example, they represented numbers 1 and 2 accurately using their fingers, but as the quantities grew larger (up to 10), their accuracy diminished. This phenomenon is also called the "analog estimation", as numbers get bigger the estimation grows.8 Their declined performance is an example of how a language can affect thought and great evidence to support the Sapir–Whorf hypothesis.
Language also seems to shape how people from different cultures orient themselves in space. For instance, many Australian Aboriginal cultures, such as the Kuuk Thaayorre, use exclusively cardinal directions ("north", "south", "east" and "west") and never define space with relative directions from the observer. Instead of using terms like "left", "right", "back" and "forward", speakers from such cultures would say, "There is a spider on your northeast leg" or "Pass the ball to the south-southwest". In fact, instead of "hello", the greeting in such cultures is, "Where are you going?" and sometimes even "Where are you coming from?" Such a greeting would be followed by a directional answer: "To the northeast in the middle distance". Using such language has the consequence that speakers need to be constantly oriented in space, or they cannot express themselves properly or even get past a greeting. Speakers of languages that rely on absolute reference frames have a greater navigational ability and spatial knowledge compared to speakers of languages that use relative reference frames. In comparison with English-speakers, speakers of languages such as Kuuk Thaayorre are also much better at staying oriented even in unfamiliar spaces, and there is strong evidence that their language is what enables them to do so.9
See also: Linguistic relativity and the color naming debate
Language may influence color processing. Having more names for different colors or different shades of colors makes it easier for both children and adults to recognize them.10 Research has found that all languages have names for black and white and that the colors defined by each language follow a certain pattern (i.e. a language with three colors also defines red; one with four defines green or yellow; and one with six defines blue, brown, and then other colors).11
The Sapir–Whorf hypothesis is the premise of the 2016 science fiction film Arrival. The protagonist explains that "the Sapir–Whorf hypothesis is the theory that the language you speak determines how you think".15
Kaplan, Abby (2016). Women Talk More than Men: … And Other Myths about Language Explained. Cambridge: Cambridge University Press. doi:10.1017/cbo9781316027141.011. ISBN 978-1-316-02714-1. 978-1-316-02714-1 ↩
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Birjandi, Parvis. "A Review of the Language-Thought Debate: Multivariant Perspectives". Islamic Azad University (Science and Research Branch) – via EBSCOhost. ↩
Pinker (2007). The Language Instinct (1994/2007). New York, NY: Harper Perennial Modern Classics. https://stevenpinker.com/publications/language-instinct ↩
Gordon, P., (2004). Numerical Cognition Without Words: Evidence from Amazonia. Science. 306, pp. 496–499. ↩
Boroditsky, Lera (June 11, 2009). "How Does Our Language Shape the Way We Think?". edge.org. https://www.edge.org/conversation/how-does-our-language-shape-the-way-we-think ↩
Schacter, Daniel L. (2011). Psychology Second Edition. New York: Worth Publishers. pp. 360–362. ISBN 978-1-4292-3719-2. 978-1-4292-3719-2 ↩
Berlin, Brent; Kay, Paul (1969). Basic Color Terms: Their Universality and Evolution. Berkeley: University of California Press. ↩
Ward, K. "General Semantics - notes on the system". Retrieved March 31, 2013. http://www.trans4mind.com/personal_development/KenGenSemantics.htm ↩
Medvedev, Danila; Davenport, Diag; Talhelm, Thomas; Li, Yin (2024). "The motivating effect of monetary over psychological incentives is stronger in WEIRD cultures". Nature Human Behaviour. 8 (3): 456–470. doi:10.1038/s41562-023-01769-5. ISSN 2397-3374. PMC 10963269. PMID 38191844. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10963269 ↩
Ralston, David A.; Cunniff, Mary K.; Gustafson, David J. (1995). "Cultural Accommodation: The Effect of Language on the Responses of Bilingual Hong Kong Chinese Managers". Journal of Cross-Cultural Psychology. 26 (6): 714–727. doi:10.1177/002202219502600612. ISSN 0022-0221. http://journals.sagepub.com/doi/10.1177/002202219502600612 ↩
"The science behind the movie 'Arrival'". Washington Post. Retrieved 2017-04-23. https://www.washingtonpost.com/national/health-science/the-science-behind-the-movie-arrival/2016/11/14/5e344114-a6a7-11e6-ba59-a7d93165c6d4_story.html ↩