Understanding one source of numerical inaccuracy: A metacognitive perspective of

the anchoring effect

Keith Dowd, SPOT lab

Consider the following items…

• Examples of experiment-provided (i.e., external) anchor items…• Do you think that the length of the Mississippi river is more or less than 1200 miles?

• Do you think the freezing point of vodka is more or less than -100 degrees Fahrenheit?

• Examples of self-generated (i.e., internal) anchor items…• What was the year in which the first president of the United States was elected?

• What was the year in which the second European explorer reached the Americas?

• All of these questions are examples of anchoring items…• The italicized portions represent the ‘comparative assessment’ (i.e., more or less)

• The underlined portions represent the external anchors (i.e., EPAs)

• Anchors can also be internally generated (i.e., SGAs)

So, what is the anchoring effect?

• The anchoring effect (Tversky & Kahneman, 1974) refers to…• The adjustment of an assessment about an unknown quantity or value towards an anchor

• This assessment is based upon previously presented external information (i.e., EPA), otherwise known as

an “anchor”

• The typical finding is that people tend to insufficiently adjust away from the anchor

• The anchoring effect has been found to reliably influence judgments across a wide variety of

domains…• Preference reversals (Chapman & Johnson, 2002)

• Legal judgments (Chapman & Bornstein, 1996)

• Probability estimates (Plous, 1989)

• Negotiation (Ritov, 1996)

• General knowledge (Chapman & Johnson, 1999)

• Thus, the anchoring effect appears to be a very robust psychological phenomenon

• So, what can we say about the processes that govern the anchoring effect?

What cognitive processes govern its operation?

• Unfortunately, details pertaining to the processes that may govern the operation of this common source of inaccuracy in everyday numerical judgments are still unclear (see Chapman & Johnson, 2002)

• Epley & Gilovich (2007) suggested that some types of anchors (i.e., SGAs) activate processes of anchoring-and-adjustment whereas others do not (i.e., EPAs).

• They argued that semantic priming is occurring in the case of EPAs rather than anchoring-and-adjustment.

• We propose that adjustment does occur with EPAs but that it does so in conjunction with SGAs and is driven by a metacognitive similarity factor between these two types of anchors.

• Because people also have the ability to think more deeply about their initial thoughts, we suggest that a

metacognitive view of the anchoring effect may be fruitful to our understanding of its operation.

• So, what exactly does this metacognitive view of anchoring have to say about the anchoring effect?

Metacognitive perspective of the anchoring effect

• When considering anchoring items, people rely on and are influenced by external anchors

(i.e., EPA) in a metacognitive fashion

• Metacognition refers to people’s thoughts about their own or others’ thoughts and thought

processes (Jost, Kruglanski, & Nelson, 1998)

• The consideration of an anchoring item causes people to spontaneously generate an internal

anchor (i.e., SGA) about that item, which is consciously accessible for further processing

• People actively compare the degree of similarity between their SGA against the EPA in order

to determine its plausibility as the correct answer for the anchoring item

• High SGA-EPA similarity may lead to less (i.e., insufficient) adjustment away from the EPA

• Low SGA-EPA similarity may be marked by greater adjustment away from the EPA

• Other metacognitive factors should also influence people’s final responses to anchoring items

• High source credibility may be marked by less adjustment away from the EPA

• Low source credibility may lead to less adjustment away from the EPA

Diagram of metacognitive model

Anchoring item is presented

SGA is spontaneously

generated

The EPA is considered and

comparative assessment is made

SGA-EPA similarity is computed and

comparison is made between anchors

Final response is rendered and

reported

Other metacognitive factors influence final responses

Predictions

1) EPAs will act to influence participants’ final responses…• Participants that are presented with high EPAs will report larger final responses than participants who are

presented with low EPAs

4) SGA-EPA similarity will predict participants’ final responses…• Participants with greater similarity between their SGA and the EPA will have larger final responses

when the EPA is high but smaller final responses when the EPA is low

3) Source credibility will predict participants’ final responses…• Participants presented with EPAs that they perceive to be derived from high credible sources will

lead to larger final responses when the EPA is high, but smaller final responses when the EPA is low

• EPAs, SGA-EPA similarity, and source credibility will interact with one another to predict participants’ final responses

• Ratings of confidence in final responses should vary as a result of the degree of SGA-EPA similarity and source credibility…

• Confidence should be greater when there is high rather than low SGA-EPA similarity• Confidence should be greater when there is high rather than low source credibility

Participants and design

• One-hundred and twenty participants…

• Students enrolled in introductory psychology courses

• Recruited through electronic participant pool

• Volunteered for credit towards their research course requirements

• The design of this experiment was a 2 (Source Credibility: high vs. low) x 2 (SGA-EPA

Similarity: high vs. low) x 2 (EPA: high vs. low) x 2 (EPA item-order: high EPA item first vs.

low EPA item first) factorial design…

• Eight experimental conditions

• Source Credibility, SGA-EPA Similarity, and EPA item-order served as between-subjects variables

• EPA served as a within-subjects variable

• Final responses and ratings of confidence served as the dependent variables

• Each experimental session consisted of six participants, each working independently of one

another in separate cubicles equipped with personal computers…

• Each session was approximately 30 minutes long

Procedures

• Participants presented with anchoring item…• Given 45 seconds to consider the anchoring item• Anchoring item described as being a trivia question administered as part of large multi-university wide

survey• Inquired about the distance a plane would travel if it were to fly from one location to another

• Participants were then required to report an absolute estimate about the distance travelled by the plane…

• This estimate served as their SGA and was used to manipulate SGA-EPA similarity• In the high EPA conditions, SGAs had an additional 7% (high SGA-EPA similarity) or 35% (low

SGA-EPA similarity) added to them• In the low EPA conditions, SGAs had an additional 7% (high SGA-EPA similarity) or 35% (low

SGA-EPA similarity) subtracted from them• These values were reported back to participants as the EPA

• EPAs were ostensibly described as being rendered from either a high credible or low credible source…

• The high credible source in this study was a senior geography major• The low credible source in this study was a senior fine arts major

• Participants asked to make comparative assessment about the EPA, report their final response, and their degree of confidence in their final response…

More procedures

• Participants presented with a battery of individual difference questionnaires…• These questionnaires were intended to erase the short-term memory for the first anchoring item

• They have no bearing on the results of this study

• Participants were then presented with another anchoring item…• The presentation of this anchoring item was similar in presentation to the first anchoring item

• Asked about the distance a plane would travel if it were to fly from one location to another but used

different locations

• The same procedures used for the first anchoring item were employed

• Finally, participants were asked to respond to several demographic questions…• These questions assessed age, gender, and academic major

• Their degree of knowledge about geography and distance was also assessed

• The order of the anchoring items was counterbalanced across experimental conditions• High anchor/low anchor presentation in conditions 1-4

• Low anchor/high anchor presentation in conditions 5-8

Results

• Results are broken down into three sections…• Preliminary analyses

• Final responses

• Ratings of confidence in final response

• Preliminary analyses…• Effect of requesting participants report their SGAs

• Effect of anchor order on final responses and confidence

• Final responses… • Main effects of EPA, SGA-EPA similarity, high/low EPA covariates

• Two-way interactions of SGA-EPA similarity x EPA, Source credibility x EPA

• Three-way interaction of SGA-EPA similarity x Source credibility x EPA

• Ratings of confidence in final responses…• Main effects of SGA-EPA similarity, Source credibility

• Unexpected three-way interaction of SGA-EPA similarity x Source credibility x EPA

Preliminary analyses

• Effect of requesting participants report their SGAs…• No difference in final responses when participants were asked to report their SGAs vs. not asked to

report their SGAs

• Effect of anchor order on final responses…• No difference in final responses when participants were presented with high/low anchors

(conditions 1-4) vs. low/high anchors (conditions 5-8)

• EPA item-order removed from further analyses on final responses

• Effect of anchor order on ratings of confidence in final responses…• No difference in final responses when participants were presented with high/low anchors

(conditions 1-4) vs. low/high anchors (conditions 5-8)

• EPA item-order removed from further analyses on ratings of confidence in final responses

Final responses

• The data were analyzed using a 2 (Source Credibility: high vs. low) x 2 (SGA-EPA Similarity:

high vs. low) x 2 (EPA: high vs. low) repeated-measures analysis of variance (ANOVA)…• Final responses were adjusted using high/low EPA covariates

• Main effects…• EPA, F(1, 207) = 31.02, p < .001

• SGA-EPA Similarity, F(1, 207) = 13.11, p < .001

• High EPA covariate, F(1, 207) = 6151.74, p < .001

• Low EPA covariate, F(1, 207) = 2691.62, p < .001

• Two-way interactions…• SGA-EPA Similarity x EPA, F(1, 207) = 144.11, p < .001

• Source Credibility x EPA, F(1, 207) = 150.87, p < .001

• Three-way interaction…• Source Credibility x SGA-EPA Similarity x EPA, F(1, 207) = 11.26, p < .001

• Pair-wise contrasts computed for high/low EPAs (see graphs)

Graphs for final responses

High EPAs Low EPAs

Ratings of confidence in final responses

• The data were analyzed using a 2 (Source Credibility: high vs. low) x 2 (SGA-EPA Similarity:

high vs. low) x 2 (EPA: high vs. low) repeated-measures analysis of variance (ANOVA)…• Unlike final responses, ratings of confidence in final responses were not adjusted using high/low EPA

covariates

• Main effects…• SGA-EPA Similarity, F(1, 210) = 9.11, p < .01

• Source Credibility, F(1, 210) = 99.54, p < .001

• Two-way interactions…• SGA-EPA Similarity x Source Credibility, F(1, 210) = 35.30, p < .001

• Unexpected three-way interaction…• Source Credibility x SGA-EPA Similarity x EPA, F(1, 210) = 8.96, p < .01

• Pair-wise contrasts computed for high/low EPAs (see graphs)

Graphs for ratings of confidence in final responses

High EPAs Low EPAs

Discussion

• Did EPAs influence final responses?• Yes! High EPAs were associated overall larger final responses than low EPAs

• Did SGA-EPA similarity predict final responses?• Yes! High SGA-EPA similarity was associated with overall larger final responses when EPAs were

high, but overall smaller final responses when EPAs were low

• Did source credibility predict final responses?• Yes! High source credibility was associated with overall larger final responses when EPAs were

high, but overall smaller final responses when EPAs were low

• Did EPA, SGA-EPA similarity, and source credibility interact with one another to predict final responses?

• Yes! A three-way interaction between these variables was found, such that high SGA-EPA similarity and high source credibility were associated with overall larger final responses when EPAs were high, but overall smaller final responses when EPAs were low

• Did ratings of confidence in final responses vary as a result of the degree of SGA-EPA similarity and source credibility?

• Yes! Greater ratings of confidence in final responses was associated with high SGA-EPA similarity and high source credibility

Thanks for listening!