Pedersen, E. J., Kurzban, R., & McCullough, M. E. (2013). Do humans really punish altruistically? A closer look. Proc. R. Soc. Lond. B, 280(1758).
Abstract: Some researchers have proposed that natural selection has given rise in humans to one or more adaptations for altruistically punishing on behalf of other individuals who have been treated unfairly, even when the punisher has no chance of benefiting via reciprocity or benefits to kin. However, empirical support for the altruistic punishment hypothesis depends on results from experiments that are vulnerable to potentially important experimental artefacts. Here, we searched for evidence of altruistic punishment in an experiment that precluded these artefacts. In so doing, we found that victims of unfairness punished transgressors, whereas witnesses of unfairness did not. Furthermore, witnesses’ emotional reactions to unfairness were characterized by envy of the unfair individual's selfish gains rather than by moralistic anger towards the unfair behaviour. In a second experiment run independently in two separate samples, we found that previous evidence for altruistic punishment plausibly resulted from affective forecasting error—that is, limitations on humans’ abilities to accurately simulate how they would feel in hypothetical situations. Together, these findings suggest that the case for altruistic punishment in humans—a view that has gained increasing attention in the biological and social sciences—has been overstated.
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Gerber, B., & Hendel, T. (2006). Outcome expectations drive learned behaviour in larval Drosophila. Proc. Roy. Soc. Lond. B Biol. Sci., 273(1604), 2965–2968.
Abstract: Why does Pavlov's dog salivate? In response to the tone, or in expectation of food? While in vertebrates behaviour can be driven by expected outcomes, it is unknown whether this is true for non-vertebrates as well. We find that, in the Drosophila larva, odour memories are expressed behaviourally only if animals can expect a positive outcome from doing so. The expected outcome of tracking down an odour is determined by comparing the value of the current situation with the value of the memory for that odour. Memory is expressed behaviourally only if the expected outcome is positive. This uncovers a hitherto unrecognized evaluative processing step between an activated memory trace and behaviour control, and argues that learned behaviour reflects the pursuit of its expected outcome. Shown in a system with a simple brain, an apparently cognitive process like representing the expected outcome of behaviour seems to be a basic feature of behaviour control.
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Hunt, G. R., & Gray, R. D. (2004). The crafting of hook tools by wild New Caledonian crows. Proc. Roy. Soc. Lond. B Biol. Sci., 271, S88–S90.
Abstract: The 'crafting' of tools involves (i) selection of appropriate raw material, (ii) preparatory trimming and (iii) fine, three-dimensional sculpting. Its evolution is technologically important because it allows the open-ended development of tools. New Caledonian crows manufacture an impressive range of stick and leaf tools. We previously reported that their toolkit included hooked implements made from leafy twigs, although their manufacture had never been closely observed. We describe the manufacture of 10 hooked-twig tools by an adult crow and its dependent juvenile. To make all 10 tools, the crows carried out a relatively invariant three-step sequence of complex manipulations that involved (i) the selection of raw material, (ii) trimming and (iii) a lengthy sculpting of the hook. Hooked-twig manufacture contrasts with the lack of sculpting in the making of wooden tools by other non-humans such as chimpanzees and woodpecker finches. This fine, three-stage crafting process removes another alleged difference between humans and other animals.
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