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UBC Theses and Dissertations

Investigating a low number prior in number perception Long, Miranda


Work in psychology and neuroscience has revealed that human newborns, young children, and many non-human animals are born with the ability to perceive number through the Approximate Number System (ANS), a specialized system for representing number (Xu & Spelke, 2000; Halberda & Feigenson, 2008; Feigenson et al., 2004; Howard et al., 2019). The ANS produces imprecise numeric representations that tend to underestimate the number of objects in a scene or display. This may appear disadvantageous, but if an observer is in a world where objects are more likely to occur in smaller numbers (e.g., 10 cookies, 6 chairs, etc.) compared to larger numbers (e.g., 1,000 bees), then a number system biased towards underestimating the number of objects might be a by-product of the human mind optimally handling the statistics of the real world (Piantadosi, 2016). Here, I utilized a Bayesian inference framework to investigate whether number perception is biased towards lower numbers (i.e., demonstrates a low number prior) given our experiences and expectations (Piantadosi 2016; Testolin et al., 2020). Additionally, I investigated whether this prior gets stronger with age. I presented a wide age range of human participants (e.g., 5-years-old to adults) with a number discrimination task where participants reported which of two sides contains more objects (e.g., “The left side has more dots”). Perceptual noise (e.g., reduced contrast) was embedded in numeric arrays to investigate whether participants were biased by their experiences and expectations for lower numbers when determining which side had more objects. Results revealed the presence of a low number prior, and that the prior does not get stronger with age in the range tested. Taken together, the current research demonstrates that the ANS is likely biased towards lower numbers because of a low number prior. The current research is the first to experimentally test for a low number prior in a wide age range of human participants.

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