Systems of logico-probabilistic reasoning characterize inference from conditional assertions that express high conditional probabilities. In this paper we investigate four prominent LP systems, the systems _O, P_, _Z_, and _QC_. These systems differ in the number of inferences they licence _. LP systems that license more inferences enjoy the possible reward of deriving more true and informative conclusions, but with this possible reward comes the risk of drawing more false or uninformative conclusions. In the first part of the paper, we (...) present the four systems and extend each of them by theorems that allow one to compute almost-tight lower-probability-bounds for the conclusion of an inference, given lower-probability-bounds for its premises. In the second part of the paper, we investigate by means of computer simulations which of the four systems provides the best balance of reward versus risk. Our results suggest that system _Z_ offers the best balance. (shrink)

In the rationality debate, Gerd Gigerenzer and his colleagues have argued that human’s apparent inability to follow probabilistic principles does not mean our irrationality, because we can do probabilistic reasoning successfully if probability information is given in frequencies, not percentages (the natural frequency hypothesis). They also offered an evolutionary argument to this hypothesis, according to which using frequencies was evolutionarily more advantageous to our hominin ancestors than using percentages, and this is why we can reason correctly about probabilities in the (...) frequency format. This paper offers a critical review of this evolutionary argument. I show that there are reasons to believe using the frequency format was not more adaptive than using the standard (percentage) format. I also argue that there is a plausible alternative explanation (the nested-sets hypothesis) for the improved test performances of experimental subjects—one of Gigerenzer’s key explananda—which undermines the need to postulate mental mechanisms for probabilistic reasoning tuned to the frequency format. The explanatory thrust of the natural frequency hypothesis is much less significant than its advocates assume. (shrink)

Viime vuosina ihmistieteiden kentässä on saanut osakseen paljon huomiota uusi lähestymistapa, jota kutsutaan ”evoluutiopsykologiaksi”. Sen piiristä on esimerkiksi väitetty, että evoluutio on muokannut meidän parinvalintamieltymyksiämme niin, että miehillä on taipumus tuntea vetoa lisääntymiskykyisiltä näyttäviin nuoriin naisiin, pyrkiä parittelemaan aina tilaisuuden tullen mahdollisimman monien naisten kanssa ja olla mustasukkaisia, kun taas naiset ovat taipuvaisia mieltymään iäkkäämpiin miehiin, joilla on valtaa ja resursseja. Luonnonvalinnalla on pyritty myös selittämään mm. raiskauksia.