What does it mean to deny the conditional statement, "if you steal an apple, you go to jail"? One theory argues that, because conditionals are probabilistic, their denials are too. And so the conditional probability, P(not-jail | steal-apple), best describes a conditional denial. Another theory argues that conditional denials concern possibilities, i.e., they activate imagined situations in which you cheat on your taxes but don’t go to jail. The two accounts make diverging predictions: only the latter predicts that people should assess conditionals and their denials as mutually inconsistent. Two experiments corroborate the possibility-based account: the studies show that both in implicit and explicit evaluations of consistency, conditional denials conflict with the conditionals they deny.

Verbs such as ‘know’ and ‘think’ help people describe mental states, and reasoners without any training in logic can make epistemic inferences about mental states. For instance, verbs such as ‘know’ are factive, i.e., they describe true propositions, and the statement Ora knows that it’s sunny licenses the inference that it’s sunny. Logicians have accordingly developed epistemic logics capable of characterizing valid and invalid epistemic inferences based on operators that serve as analogs to verbs such as ‘know’ and ‘think’. Recent work suggests that no existing logical system can capture the inferences that naïve individuals tend to make. This paper describes a new theory of epistemic reasoning that operates on the assumption that reasoners represent epistemic relations as spatial models. The theory accords with recent theoretical advances, existing data, as well as two novel experiments that show how reasoners cope with nested epistemic verbs, e.g., Ami knows that Ora thinks it’s sunny.

When people think about the features of common objects, like scissors, they often spontaneously recall a central feature: scissors cut things. They tend not to recall other features of scissors, e.g., that they have handles. The present paper posits a novel explanation for the behavior: the features people recall first and most often reflect semantic generalizations of kinds. A recent taxonomy of such generalizations suggests that people represent privileged links between kinds and their features known as principled connections (Prasada et al., 2013). Several tests diagnose principled connections: for instance, principled connections reflect norms, so one way to diagnose the presence of a principled connection is to test the acceptability of sentences of the form all normal Xs have feature Y, as in all normal cars have four wheels. We tested whether participants accept generalizations about the normality of features produced in a semantic feature production task (Experiments 1 and 2) as well as self-referential generalizations (Experiment 3). The experiments provided participants with generalizations about features listed first and most often as well as features that people list less frequently. They found that people readily accepted generalizations that diagnose the presence of principled connections. The results corroborate the view that principled connections help people recall the features of conceptual categories.

While many formal frameworks distinguish between desires and intentions, and considerable empirical work shows that people interpret them differently, no studies examine how people reason about them. We extend Harner and Khemlani’s (2020) model-based theory of relations describing desire. The theory holds that people represent desires, as in, e.g., Pav wants to visit Angkor Wat, by pairing a factual representation of the negation of the desire (e.g., that Pav is not currently visiting Angkor Wat) with a future possibility where the desire is realized. We propose that intentions, which people express using verbs like plan, are represented as future actions that agents seek to perform. A particular individual’s plans must be consistent with one another, whereas desires can conflict with these plans. We show how the model theory distinguishes desires and intentions, namely that models can be coherent even when a desire and a plan are inconsistent with each other. The distinctions make predictions about how reasoners should assess the consistency of statements concerning desires and intentions, and we report on two experiments that validate them.

Children’s production of mental state verbs is studied to research their theory of mind and general cognitive development. Desire verbs are a rich resource as children produce them frequently and early in development, with ‘want’ being of the most frequent production. We report on a corpus study of 450+ instances of ‘want’ as gathered from dialogues with children in CHILDES. We describe a novel coding scheme that measures the semantic development of ‘want’ utterances, such as the use of negation, clause type, complement subject, and the semantic type of the complement, in addition to more conventional categories. We report on these features’ frequencies for children aged 2-4. Noteworthy findings suggest that children talk about their own desires most often, but as they grow older, they talk more about others’ desires; they desire more complex objects as they mature; and they primarily use questions to talk about second person desires.

Children’s production of mental state verbs can reveal evidence of their theory of mind and general cognitive development. Children produce a certain class of mental state verbs, namely desire verbs such as want, wish, and hope, early in development. Among these desire verbs, they produce want the most frequently. We report on a corpus study of 450+ instances of want as gathered from children’s dialogues with caretakers in the CHILDES database. We developed a novel coding scheme to measure children’s use and understanding of want utterances: i.e., we sought to track the contents of their desires and the agents children predicated desires about. We report on the frequencies of these features across the ages of 2- 4, and highlight noteworthy trends in the way children learn to use want. Children appear to talk about their own desires most often; they primarily use questions to talk about second person desires; and they desire more complex objects as they mature. We describe how these patterns of linguistic competency may serve as an index of a developing theory of mind.

Certain generalizations are teleological, e.g., forks are foreating. But not all properties relevant to a particular conceptpermit teleological generalization. For instance, forks getwashed roughly as often as they’re used for eating, yet thegeneralization, forks are for washing, might strike reasoners asunacceptable. What explains the discrepancy? A recenttaxonomic theory of conceptual generalization (Prasada, 2017;Prasada & Dillingham, 2006; Prasada et al., 2013) argues thatcertain kinds of conceptual connections – known as“principled” connections – license generalizations, whereasassociative, “statistical” connections license only probabilisticexpectations. We apply this taxonomy to explain teleologicalgeneralization: it predicts that acceptable teleologicalgeneralizations concern concept-property pairs in which theconcept bears a principled connection to a property. Under thisanalysis, the concept fork bears a principled connection toeating and a statistical connection to washing. Twoexperiments and a regression analysis tested and corroboratedthe predictions of the theory.