Cognitive Evolution Laboratory

Egnor, S.E.R. & Hauser, M.D. (in press): Noise-induced vocal modulation in cotton-top tamarins (Saguinus oedipus). Abstract:

The Lombard effect—an increase in vocalization amplitude in response to an increase in background noise—is observed among a wide variety of animals. We investigated this basic form of vocal control in the cotton-top tamarin (Saguinus oedipus) by measuring the amplitude of a contact call, the combination long call, while simultaneously varying the background noise level. All subjects showed a significant increase in call amplitude and syllable duration in response to an increase in background noise amplitude. Together with prior results, this study shows that tamarins, have greater vocal control in the context of auditory feedback perturbation than previously suspected.

Hauser, M.D. & Spaulding, Bailey. (2006): Wild rhesus monkeys generate causal inferences about possible and impossible physical transformations in the absence of experience. In: Proceedings of the National Academy of Sciences, 103:18. Abstract:

Human infants and adults generate causal inferences about the physical world from observations of single, novel events, thereby violating Hume’s thesis that spatiotemporal cooccurrence from prior experience drives causal perception in our species. Is this capacity unique or shared with other animals? We address this question by presenting the results of three experiments on freeranging rhesus monkeys (Macaca mulatta), focusing specifically on their capacity to generate expectations about the nature of completely unfamiliar physical transformations. By using an expectancy violation looking-time method, each experiment presented subjects with either physically possible or impossible transformations of objects (e.g., a knife, as opposed to a glass of water, appears to cut an apple in half). In both experiments, subjects looked longer when the transformation was impossible than when it was possible. Follow up experiments ruled out that these patterns could be explained by association. These results show that in the absence of training or direct prior experience, rhesus monkeys generate causal inferences from single, novel events, using their knowledge of the physical world to guide such expectations.

Hauer, M.D., Young, L., & Cushman, F. (in press): Reviving Rawls' Linguistic Analogy: Operative principles and the causal structure of moral actions. In Moral Psychology and Biology. Abstract:

The thesis we develop in this essay is that all humans are endowed with a moral faculty. The moral faculty enables us to produce moral judgments on the basis of the causes and consequences of actions. As an empirical research program, we follow the framework of modern linguistics. 1 The spirit of the argument dates back at least to the economist Adam Smith (1759/1976) who argued for something akin to a moral grammar, and more recently, to the political philosopher John Rawls (1971). The logic of the argument, however, comes from Noam Chomsky’s thinking on language specifically and the nature of knowledge more generally (1986; 1988; 2000; Saporta, 1978).

Hauser, M.D et. al (in press): A Dissociation Between Moral Judgments and Justifications. In: Mind & Language. Abstract:

To what extent do moral judgments depend on conscious reasoning from explicitly understoodprinciples? We address this question by investigating one particular moral principle, the principle of the double effect. Using web-based technology, we collected a large data set on individuals’ responses to a seriesof moral dilemmas, asking when harm to innocent others is permissible. Each moral dilemma presented a choice between action and inaction, both resulting in lives saved and lives lost. Results showed that: [1]patterns of moral judgments were consistent with the principle of double effect and showed little variation across differences in gender, age, educational level, ethnicity, religion or national affiliation [within thelimited range of our sample population] and [2] a majority of subjects failed to provide justifications that could account for their judgments. These results indicate that the principle of the double effect may beoperative in our moral judgments but not open to conscious introspection. We discuss these results in light of current psychological theories of moral cognition, emphasizing the need to consider the unconscious appraisalsystem that mentally represents the causal and intentional properties of human action.

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