Paul Bloom

Natural language and natural selection

Many people have argued that the evolution of the human language faculty cannot be explained by Darwinian natural selection. Chomsky and Gould have suggested that language may have evolved as the by-product of selection for other abilities or as a consequence of as-yet unknown laws of growth and form. Others have argued that a biological specialization for grammar is incompatible with every tenet of Darwinian theory – that it shows no genetic variation, could not exist in any intermediate forms, confers no selective advantage, and would require more evolutionary time and genomic space than is available. We examine these arguments and show that they depend on inaccurate assumptions about biology or language or both. Evolutionary theory offers clear criteria for when a trait should be attributed to natural selection: complex design for some function, and the absence of alternative processes capable of explaining such complexity. Human language meets these criteria: Grammar is a complex mechanism tailored to the transmission of propositional structures through a serial interface. Autonomous and arbitrary grammatical phenomena have been offered as counterexamples to the position that language is an adaptation, but this reasoning is unsound: Communication protocols depend on arbitrary conventions that are adaptive as long as they are shared. Consequently, language acquisition in the child should systematically differ from language evolution in the species, and attempts to analogize them are misleading. Reviewing other arguments and data, we conclude that there is every reason to believe that a specialization for grammar evolved by a conventional neo-Darwinian process.

Social evaluation by preverbal infants

The capacity to evaluate other people is essential for navigating the social world. Humans must be able to assess the actions and intentions of the people around them, and make accurate decisions about who is friend and who is foe, who is an appropriate social partner and who is not. Indeed, all social animals benefit from the capacity to identify individual conspecifics that may help them, and to distinguish these individuals from others that may harm them. Human adults evaluate people rapidly and automatically on the basis of both behaviour and physical features, but the ontogenetic origins and development of this capacity are not well understood. Here we show that 6- and 10-month-old infants take into account an individual’s actions towards others in evaluating that individual as appealing or aversive: infants prefer an individual who helps another to one who hinders another, prefer a helping individual to a neutral individual, and prefer a neutral individual to a hindering individual. These findings constitute evidence that preverbal infants assess individuals on the basis of their behaviour towards others. This capacity may serve as the foundation for moral thought and action, and its early developmental emergence supports the view that social evaluation is a biological adaptation.

Two reasons to abandon the false belief task as a test of theory of mind

The false belief task has often been used as a test of theory of mind. We present two reasons to abandon this practice. First, passing the false belief task requires abilities other than theory of mind. Second, theory of mind need not entail the ability to reason about false beliefs. We conclude with an alternative conception of the role of the false belief task.

Conservatives are more easily disgusted than liberals

The uniquely human emotion of disgust is intimately connected to morality in many, perhaps all, cultures (Rozin, Lowery, Imada, & Haidt, 1999b). We report two studies suggesting that a predisposition to feel disgust (“disgust sensitivity”) is associated with more conservative political attitudes, especially for issues related to the moral dimension of purity. In the first study, we document a positive correlation between disgust sensitivity and self-reported conservatism in a broad sample of US adults. In Study 2 we show that while disgust sensitivity is associated with more conservative attitudes on a range of political issues, this relationship is strongest for purity-related issues—specifically, abortion and gay marriage.

Attribution of Dispositional States by 12-Month-Olds

The ability to interpret the behavior of other individuals is essential for effective social functioning. Many investigators now believe that even young infants can recognize that agents act toward goals. Here we report three experiments suggesting that 12-month-old infants not only can recognize goal-related action, but also can interpret future actions of an actor on the basis of previously witnessed behavior in another context. The possibility that this inference is made through the attribution of mental states is discussed.

Three-Month-Olds Show a Negativity Bias in Their Social Evaluations.

Previous research has shown that 6-month-olds evaluate others on the basis of their social behaviors--they are attracted to prosocial individuals, and avoid antisocial individuals (Hamlin, Wynn & Bloom, 2007). The current studies investigate these capacities prior to 6 months of age. Results from two experiments indicate that even 3-month-old infants evaluate others based on their social behavior towards third parties, and that negative social information is developmentally privileged.

How infants and toddlers react to antisocial others

Although adults generally prefer helpful behaviors and those who perform them, there are situations (in particular, when the target of an action is disliked) in which overt antisocial acts are seen as appropriate, and those who perform them are viewed positively. The current studies explore the developmental origins of this capacity for selective social evaluation. We find that although 5-mo-old infants uniformly prefer individuals who act positively toward others regardless of the status of the target, 8-mo-old infants selectively prefer characters who act positively toward prosocial individuals and characters who act negatively toward antisocial individuals. Additionally, young toddlers direct positive behaviors toward prosocial others and negative behaviors toward antisocial others. These findings constitute evidence that the nuanced social judgments and actions readily observable in human adults have their foundations in early developing cognitive mechanisms.

The Intelligence of the Moral Intuitions: Comment on Haidt (2001)

The social intuitionist model (J. Haidt, 2001) posits that fast and automatic intuitions are the primary source of moral judgments. Conscious deliberations play little causal role; they are used mostly to construct post hoc justifications for judgments that have already occurred. In this article, the authors present evidence that fast and automatic moral intuitions are actually shaped and informed by prior reasoning. More generally, there is considerable evidence from outside the laboratory that people actively engage in reasoning when faced with real-world moral dilemmas. Together, these facts limit the strong claims of the social intuitionist model concerning the irrelevance of conscious deliberation.

Intention and analogy in children's naming of pictorial representations.

What underlies childrens naming of representations, such as when they call a statue of a clothespin “a clothespin”? One possibility is that they focus exclusively on shape, extending the name “clothespin” only to entities that are shaped like typical clothespins. An alternative possibility is that they extend a word that refers to an object to any representation of that object, and that shape is relevant because it is a reliable indicator of representational intent. We explored these possibilities by asking 3- and 4-year-olds to describe pictures that represented objects through intention and analogy. The results suggest that it is childrens appreciation of representation that underlies their naming; sameness of shape is neither necessary nor sufficient. We conclude by considering whether this account might apply more generally to artifacts other than pictorial representations.

Enumeration of collective entities by 5-month-old infants

Recent findings suggest that infants are capable of distinguishing between different numbers of objects, and of performing simple arithmetical operations. But there is debate over whether these abilities result from capacities dedicated to numerical cognition, or whether infants succeed in such experiments through more general, non-numerical capacities, such as sensitivity to perceptual features or mechanisms of object tracking. We report here a study showing that 5-month-olds can determine the number of collective entities -- moving groups of items -- when non-numerical perceptual factors such as contour length, area, density, and others are strictly controlled. This suggests both that infants can represent number per se, and that their grasp of number is not limited to the domain of objects.