I urval från Stockholms universitets publikationsdatabas

• Parental effects on sexual preferences in humans

  Hanna Aronsson (et al.).

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• Male height and marital status

  2017. Kimmo Sorjonen, Magnus Enquist, Bo Melin. Personality and Individual Differences 104, 336-338

  Artikel

  Using conscription data and follow ups from a large representative sample of Swedish men, and in accordance with earlier studies, we found a bell shaped association between male height and the hazard-for not being unmarried. The shape of this association was not affected by indicators of health and socioeconomic status and it might, instead, be due to microeconomic factors such as supply and market value. A negative linear association between male height and the hazard for divorce once married was also found, and this association was accounted for by indicators of socioeconomic status.

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• Memory for stimulus sequences

  2017. Stefano Ghirlanda, Johan Lind, Magnus Enquist. Royal Society Open Science 4 (6)

  Artikel

  Humans stand out among animals for their unique capacities in domains such as language, culture and imitation, yet it has been difficult to identify cognitive elements that are specifically human. Most research has focused on how information is processed after it is acquired, e.g. in problem solving or 'insight' tasks, but we may also look for species differences in the initial acquisition and coding of information. Here, we show that non-human species have only a limited capacity to discriminate ordered sequences of stimuli. Collating data from 108 experiments on stimulus sequence discrimination (1540 data points from 14 bird and mammal species), we demonstrate pervasive and systematic errors, such as confusing a red-green sequence of lights with green-red and green-green sequences. These errors can persist after thousands of learning trials in tasks that humans learn to near perfection within tens of trials. To elucidate the causes of such poor performance, we formulate and test a mathematical model of non-human sequence discrimination, assuming that animals represent sequences as unstructured collections of memory traces. This representation carries only approximate information about stimulus duration, recency, order and frequency, yet our model predicts non-human performance with a 5.9% mean absolute error across 68 datasets. Because human-level cognition requires more accurate encoding of sequential information than afforded by memory traces, we conclude that improved coding of sequential information is a key cognitive element that may set humans apart from other animals.

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• Time Does Not Help Orangutans Pongo abelii Solve Physical Problems

  2017. Johan Lind (et al.). Frontiers in Psychology 8

  Artikel

  Many questions in animal intelligence and cognition research are challenging. One challenge is to identify mechanisms underlying reasoning in experiments. Here, we provide a way to design such tests in non-human animals. We know from research in skill acquisition in humans that reasoning and thinking can take time because some problems are processed in multiple steps before a solution is reached (e.g., during mental arithmetics). If animals are able to learn through similar processes their decision making can be time consuming, and most importantly improve if more time to process information is allowed. We tested if performance of two Sumatran orangutans (Pongo abelii) increased in a two-choice experiment when they were allowed extra time before making their decisions, compared to when they were forced to decide immediately. We found that the performance of the orangutans did not depend on the time they were allowed to process the information before making their decisions. This methodology provides a potential avenue for empirical tests of mechanisms underlying reasoning in non-human animals.

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