Author Archives: Nicholas Shackel

Bias not a bug but a feature?

From here: an article discussing the benefits of biases

""Biased mechanisms are not design defects of the human mind, but rather design features," …Haselton likens a biased decision pathway to a smoke alarm that can make one of two errors. It can go off in the absence of fire—a false positive: irritating, but far from lethal. The more dangerous error is the false negative, which fails to signal a real fire. "Engineers can’t minimize both errors, because there’s a trade-off," explains Haselton. "If you lower the threshold for noting fires, you’re going to have more false alarms. Natural selection created decision-making adaptations not to maximize accuracy but to minimize the more costly error."

"Glenn Geher, an associate professor of psychology at SUNY at New Paltz, who, with Miller, edited a forthcoming volume on mating intelligence, is developing a mathematical model to demonstrate what many a grandmother has long cautioned: Women who are de facto skeptical of a man’s intentions are almost always better off than women who spend hours deconstructing the first date. ("He gave me his home number, he asked about my family, he mentioned a concert this spring—he must be into me!") Geher found that if a woman cannot accurately judge a man’s romantic designs at least 90 percent of the time, she’s better off being biased. "Women using a ‘men are always pigs’ decision-making rule may be more likely to actually end up with honest, committed, and long-term-seeking males," insists Geher."

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Disagreement at Thoughts, Arguments and Rants

Some time ago I offered an argument for the possibility of reasonable disagreement over philosophical positions. Brian Weatherson at TAR has just posted a paper with an interesting argument for a similar conclusion: here.  He is discussing the position of Feldman, Christensen and Elga, also held by Robin and some others here, that finding an epistemic peer disagreeing with you should weaken your belief.   Brian is using a strategy that is often effective at refuting a philosophical theory: seeing whether the theory can coherently apply to itself.

This equal weight view, hereafter EW, is itself a philosophical position. And while some of my friends believe it, some of my friends do not. (Nor, I should add for your benefit, do I.) This raises an odd little dilemma. If EW is correct, then the fact that my friends disagree about it means that I shouldn’t be particularly confident that it is true, since EW says that I shouldn’t be too confident about any position on which my friends disagree. But, as I’ll argue below, to consistently implement EW, I have to be maximally confident that it is true. So to accept EW, I have to inconsistently both be very confident that it is true and not very confident that it is true. This seems like a problem, and a reason to not accept EW. (Weatherson online pdf:1)

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Discussions of Bias in answers to the Edge 2007 Question

The new answers to the Edge 2007 Question ‘What are you optimistic about’ contain several discussions of bias. I’ve excerpted a few quotations below, about pessimism caused by the media’s bad news bias and bias in social science caused by political belief.

Continue reading "Discussions of Bias in answers to the Edge 2007 Question" »

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Normative Bayesianism and Disagreement

Normative Bayesianism says that you ought to believe as you would if you were an ideal Bayesian believer and so believing is what it is to believe rationally. An ideal Bayesian believer has (1) beliefs by having credences, where a credence is a degree of belief in a proposition; (2) has a Prior = a complete consistent set of credences (capitalized to avoid confusing priors = a person’s credences with Priors = a plurality of complete consistent sets of credences), that is to say, has a credence function from the sigma algebra of propositions into the reals such that the credence function is a measure that is a probability function; (3) changes his beliefs on the basis of the evidence he has acquired by updating his credence function by the use of Bayes’ theorem.

Much of the earlier discussion about the rationality of disagreement and the requirement of modesty was advanced on the basis of the claim that Bayesian believers cannot rationally disagree. But there are different versions of what precisely that claim might be.

Strong Bayesian Agreement: Ideal Bayesian believers who have common knowledge of each others opinion of a proposition agree on that proposition.

Moderate Bayesian Agreement: Ideal Bayesian believers who have rational Priors and common knowledge of each others opinion of a proposition agree on that proposition.

Weak Bayesian Agreement: Ideal Bayesian believers who have a common Prior and common knowledge of each others opinion of a proposition agree on that proposition.

Continue reading "Normative Bayesianism and Disagreement" »

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Reasonable Disagreement

In his recent post Robin suggests that Van Inwagen is biased in his philosophical beliefs about free will, possible worlds and the nature of persons, on the grounds that to disagree with as clever a philosopher as Lewis (rather than suspend judgement, for example) cannot be reasonable. In the paper referenced, Van Inwagen concedes that he is not arguing that any particular philosophical positions are justified, just asserting that he believes some are. Van Inwagen’s main point is in fact that the use made of Clifford’s dictum (in brief, it is always wrong to believe on insufficient evidence) is biased, since it is applied to religious belief but not to other beliefs. Nevertheless, I think we could construct on Van Inwagen’s behalf an argument for the reasonableness of his disagreement with Lewis.

  1. Philosophers have no consensus on many important philosophical questions.
  2. Their disagreement cannot be adequately explained on the basis of communicable beliefs (even allowing for the general underdetermination of answers to philosophical questions by the considerations available).
  3. Therefore we must allow of there being incommunicable beliefs (which, when true, are incommunicable insights).
  4. There is no reason to think that philosophers are irrational.
  5. Both Lewis’s and my philosophical positions are justified with respect to their evidential bases.
  6. We have both examined everything we know to be relevant to the question at issue.
  7. Among the evidential base of justified philosophical belief are states that are either incommunicable insights or states we are unable to distinguish from such insights but whose content is erroneous.
  8. What can be communicated between us has not led either of us to realise that something we took to be an insight is an error.
  9. Therefore we can reasonably disagree.

He might also have further defended this by arguing that unless we are prepared to be accept that none of our beliefs are justified (i.e. to be a certain kind of sceptic), a similar story has to be told for all of our beliefs: that their evidential base may not be entirely communicable and the justificational relations may not be entirely transparent to us.

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