Human Cognition: A Developmental Account of Human Reasoning Skills

Student thesis: Phd


Reasoning has previously been thought of as an individual skill, such as solving problems through logic and evidence. However, recent accounts redefine reasoning as a social skill, where speakers exchange reasons for their beliefs to collectively solve problems (Mercier & Sperber, 2011; Tomasello, 2019). How young children's reasoning emerges and changes across development has been under-investigated in experimental studies, as most evidence comes from naturalistic studies. Furthermore, previous literature focused on how children communicate their reasons verbally. However, reasons can also be communicated non-verbally, e.g., through gestures. Therefore, within this thesis I provide a developmental account of reasoning that investigates these areas. First, in Chapter 1, I outline relevant theories, review the literature, and present the thesis aims. Then, Chapter 2 presents a research paper with two online studies where I investigated whether and how young children could hold two solutions and perspectives in mind when reasoning with evidence. Study 1 investigated whether preschool children could hold two solutions in mind (why one solution works better than the other) when reasoning with evidence. Two-, 3- and 4-year-old children could infer the location of a toy through reasoning by exclusion: 'it cannot be there (solution A) so it must be in here (solution B).' Study 2 investigated whether 3- and 5-year-old children could hold two perspectives in mind (their perspective and their partner's perspective) to communicate their reasoning about evidence nonverbally. Children teamed up with an adult partner to jointly decide which out of two characters took an item (e.g., drank milk). Five-year-olds, and 3-year-olds to a lesser extent, could produce point-to-self gestures as reasons (pointed at their lip to show the milk moustache to direct their partner's attention to the location of the evidence on a character). In Chapter 3, I investigated how children produce verbal reasons to convince a partner during collaborative decision making. This chapter presents a published paper that investigated whether 5- and 7-year-old children could produce reasons about information reliability, "meta-talk", during collaborative problem solving. In Study 1, peer dyads heard two informants give conflicting information about the needs of a novel animal. One prefaced her claim with "I know", other prefaced her claim with "I think", so the former was more reliable than the latter. Children were tasked with jointly deciding which items the animal needed. Both 5- and 7-year-old children could settle on the items suggested by the reliable informant by referring to information reliability or using meta-talk (e.g., "it eats sand because she said she knows it"). In Study 2, 3- and -5-year-old children searched for a toy with an adult partner making incorrect proposals. Children refuted their partner's reasoning through explaining what they witnessed (e.g., It cannot be there because "I saw it move", "she moved it"). Overall, these findings contribute crucial knowledge to our understanding of the developmental trajectory of children's reasoning. By age 5, and less reliably by age 3, children communicate their reasoning in advanced forms both verbally and nonverbally. Children can consider their partner's perspective and produce point-to-self gestures to communicate about evidence and begin to produce meta-talk explaining their knowledge access during collaborative decision making. In Chapter 4, I present an updated developmental picture, discuss some of the limitations of this research and suggest some future directions.
Date of Award31 Dec 2022
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorAnna Theakston (Supervisor) & Bahar Köymen (Supervisor)


  • verbal reasoning
  • non-verbal reasoning
  • peer interactions
  • social development
  • collaborative decision-making
  • reasoning
  • cognitive development

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