Language facilitates 2.5-year-olds’ reasoning by the disjunctive syllogism

AbstractChildren and animals successfully reason by elimination: if a reward is hidden in A or B, and they see A empty, they search in B (Call, 2004; Hill et al., 2012). Twenty-seven-month-olds also solve similar tasks when “emptiness” is conveyed verbally, through negation (“The toy is not in the box”, Feiman et al., 2017). However, it is unclear whether participants solved these tasks with the disjunctive syllogism (A OR B, NOT A, THEREFORE B); in a 4-cup paradigm requiring disjunctive reasoning only 3-5-year-olds –but not 2.5-year-olds –succeeded (Mody & Carey, 2016). We used a linguistic version of the 4-cup task to examine children’s ability to reason disjunctively using verbal negation. We found that 3- and 2.5-year-olds performed significantly above chance (58.1%, 54.2%, respectively, ps’<.05). Thus, presenting the negative premise verbally facilitated 2.5-year-olds deductions. We conclude that older 2-year-olds have a robust understanding of negation, which they apply in abstract reasoning.

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