This dissertation explores how mathematics is acquired in the mind, examining which skills are present early in development and which require cultural input to emerge. Research on mathematical cognition has traditionally been based on WEIRD (Western, Educated, Industrialized, Rich, Democratic) populations. These populations are not representative of the diversity of human thought, and can lead to inaccurate generalizations about the factors supporting mathematical understanding. This dissertation explores the origins of mathematical abilities in the Tsimane’, an indigenous group in the Bolivian Amazon. Individual Tsimane’ have variable levels of formal schooling, market experience, language for mathematical concepts, and other cultural supports. This variability helps to arbitrate between innate and environmental factors giving rise to mathematical cognition. Throughout the dissertation, a cross-cultural lens is applied to research the origins of three key mathematical abilities: counting, arithmetic, and geometry.

Humans possess a metacognitive sense of certainty which, for better or worse, influences behavior. This sense of certainty is often misleading and can leave us vulnerable to believing false information. In this dissertation, I study how humans form their sense of certainty and the types of false beliefs which we can be at times, highly certain of. This work spans across multiple domains, including concept learning, word-meaning, pseudoscience, and people’s metacognitive beliefs. Across seven experiments, I present empirical evidence that learners use heuristics over idealized model-based features when forming their sense of certainty, and that this leaves us prone to errors which can result in the adoption of misinformed beliefs as drastic as the belief that the Earth is flat.