In the prototypical anchoring and adjustment paradigm (e.g., Kahneman and Tversky 1974) experimenters ask participants to figure out numerical values for some arbitrary
questions, like ‗How old was Gandhi when he died?‘,49
‗What is the freezing point of
vodka?‘,50
‗When was George Washington elected president?‘51, What percentage of the UN
is made up of African nations?‘.52 Before participants are allowed to answer the target
question, the experimenter arbitrarily selects a number (e.g. by spinning a wheel, or by using the participants social security number, or by a randomly chosen card, etc.) which serves as an ‗anchor.‘ Importantly, the participants are made aware that the number selected is indeed arbitrarily selected (by, e.g., making the participants spin the wheel or choose the random card). Participants are then asked whether the answer to the target question is higher or lower than the arbitrarily picked number. (Say the number that came up on the wheel was 1776. Participants would then be asked, e.g., whether George Washington was elected president before or after 1776.) After answering this question, participants are then allowed to give an exact answer to the original question. The randomly generated anchors make a significant
49
Gandhi died at 78.
50 For 80 proof vodka it‘s approximately -16.51 Fahrenheit. 51 He was elected in 1779.
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impact on the subjects‘ answers.53
For example, people will guess that Gandhi died at 50 if they first had to decide whether he died before or after he was 9, and they‘ll think he died at 67 if they receive 140 as the anchor (Strack and Mussweiler 1997).
Explanations of the anchoring and adjustment effect are scant at best. For example, the traditional ‗explanation‘ of the effect is that people anchor on a value and then adjust up or down from that value (Kahneman and Tversky 1974). This explanation is just a
restatement of the phenomenon (not that the authors didn‘t realize this—as they mention, they just didn‘t have any other explanation on offer). Since then, the main explanation of the effect is that it is produced by ―increased accessibility of anchor-consistent information‖ (Epley and Gilovich 2001, Mussweiler and Strack 1999, 2000). Although this may seem like a novel explanation, it is just an instance of a broader trend, the bias towards searching for confirmatory evidence, the confirmation bias. Hence, the confirmation bias is supposed to explain the anchoring and adjustment effect. But as we‘ve just seen in section 3.2, the confirmation bias itself presupposes the Spinozan theory. The confirmation bias is only
supposed to be in play when we are searching for evidence to confirm an already held belief,
so by accepting the confirmation bias explanation the non-Spinozan theorist just doubles her mysteries, for she‘d also need to explain why merely contemplated hypotheses are believed. But the Spinozan theory can alleviate these mysteries. Anchoring and adjustment effects arise because participants believe that the anchor they‘re given is actually the answer to the question they‘re posed. Participants believe that the anchors are the correct answer because
they merely consider that possibility, and consideration causes belief.54
53 The participants generally move halfway towards the anchors as compared to participants that don‘t
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One may object to this explanation on the grounds that anchor consistent information becomes more available not because of the confirmation bias, but instead because of mere semantic priming. Maybe one‘s ‗accumulator‘ (see Gallistel and Gelman 1992) is active when the number 140 comes up, and this primes other closer numbers. Or perhaps it‘s one‘s symbol for 140 that arises and primes other closer numbers. However, there are two reasons to discard this objection. For one, if the numerical priming story were true, then we‘d expect what participants do when they adjust is to continually slide along the number line until they
reach a limit, one presumably dictated by the extent of the priming effect.55 However, the one
study I know of which has attempted to test whether the adjustment process is serial or continuous (like the priming story would suppose), Epley and Gilovich (2001), have data which speaks against the priming/sliding view and propose instead that the adjustment phase is a series of jumps, which are ―discreet minadjustments coupled with hypothesis tests‖ (Epley et al. 2004, p. 328). Such jumps do not seem to be explicable on the priming hypothesis.
More direct evidence against the priming explanation comes from Chapman and Johnson (2002). They point out that not any old numerical value will cause the anchoring and adjustment effect—rather the arbitrary numerical value has to be considered relevantly related to the question at hand, even if it‘s a grossly unreasonable value. For example, say I asked you to consider what the average income of a New Yorker is. Before you answer this
54 Here, as elsewhere, lies a tacit ceteris paribus clause. When participants are asked a question and then given
the anchor the participants must form a thought that turns the interrogative into a declarative. Presumably, most participants do this automatically. If participants did not make such a transformation then the given explanation wouldn‘t hold (and presumably the participants‘ answers wouldn‘t show the anchoring and adjustment effect. Evidence for this claim follows immediately below in the discussion of the Chapman and Johnson.).
55 This has been shown to be the process by which numerical priming works (see, e.g., Dehaene 1997), thus
explaining why size and distance effects arise in numerical priming experiments (Moyer and Landauer 1967; Meck and Church 1983).
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question, I ask you to spin the wheel to generate an anchor and the wheel comes up with the number 90,000. Now here‘s the important part: if the intermediate question is orthogonal to the original question, the anchoring and adjustment phenomenon will not arise. Suppose after the wheel spits out 90,000 I ask you if 90,000 is greater or less than the square footage of
Buckingham Palace and you answer in whatever way you deem correct.56 Suppose further
that after answering this comparison question we return to the original question of the average income of a New Yorker. In this case the arbitrarily derived anchor will not affect your subsequent judgment. The anchors only affect your judgments when the anchors are understood as related, even if unreasonably so, to the question that you are considering. In other words, you have to complete a thought that involves the anchor as the answer to the question you are considering. Of course, this is decidedly not the way that priming works. Priming works by mere associative activations (or ‗construct activations‘) spreading through one‘s cognitive system. So, if the anchor was just working as a prime we‘d expect it to work regardless of what question a person is considering, however that is not how the anchoring and adjustment paradigm works, so we can be satisfied that priming is not the explanation of the anchoring and adjustment effect. The only contender explanation is the Spinozan theory, thus lending strong evidence in favor of theory. The anchoring and adjustment effect is as robust an effect as we find across the literature. A theory which is independently plausible and can explain this effect should be taken quite seriously.
It is worth noting that I‘m not the first to propose that the anchoring and adjustment effect arises because participants believe that the anchor is the answer to the question they‘re considering. Jacowitz and Kahneman (1995) also floated this explanation. However, they did so not for architectural reasons, like the Spinozan theory does, but instead for Gricean
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pragmatic reasons. Jacowitz and Kahneman suppose that participants‘ reason that
experimenters wouldn‘t give them the anchors if the anchors were truly irrelevant. Thus,
Jacowitz and Kahneman suppose that participants believe that the anchors are good answers
for (broadly speaking) rational reasons. This seems utterly implausible. If the subjects are
going to end up believing that Gandhi lived to 140, our principles of charity should dictate that they don‘t reason their way there. When subjects see that the anchors are created from their (e.g.) social security number, do we really want to say that they then surmise that this is the correct answer? After all, it is often the participants themselves who (e.g.,) spin the wheel of fortune thus seeing exactly how arbitrarily derived the anchor actually is. By supposing that participants reason their way to believing that the anchor is (more or less) the correct answer we attribute to the participants not just a smidgen of irrationality (which is often reasonable to do) but instead massive stupidity. People may be unreasonable in all sorts of circumstances, but if we grant them Jacowitz and Kahneman‘s suggested patterns of
reasoning, we‘d have to suppose that they are absolute idiots, a conclusion which strikes even my cynical ears as implausible.
A more reasonable supposition is that subjects, in the first instance, don‘t have a choice about what they believe. They end up believing that Gandhi lived to 140 because they are forced to believe so by the architectural set up of the mind and not because they follow some very suspicious logic based on a leap of faith in the experimenters‘ intentions (and skill at deriving a correct answer from a subject‘s license!). In sum, it is reasonable to conclude that the Spinozan theory is the only reasonable explanation of the vast anchoring and
adjustment data.57
57
As advertised earlier, I will now return to the discussion about extending the anchoring and adjustment explanations to cover seemingly unrelated phenomena. The following case study should suffice to show the
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