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. 2014 Jul 9;9(7):e99557.
doi: 10.1371/journal.pone.0099557. eCollection 2014.

Opinion dynamics with confirmation bias

Affiliations

Opinion dynamics with confirmation bias

Armen E Allahverdyan et al. PLoS One. .

Abstract

Background: Confirmation bias is the tendency to acquire or evaluate new information in a way that is consistent with one's preexisting beliefs. It is omnipresent in psychology, economics, and even scientific practices. Prior theoretical research of this phenomenon has mainly focused on its economic implications possibly missing its potential connections with broader notions of cognitive science.

Methodology/principal findings: We formulate a (non-Bayesian) model for revising subjective probabilistic opinion of a confirmationally-biased agent in the light of a persuasive opinion. The revision rule ensures that the agent does not react to persuasion that is either far from his current opinion or coincides with it. We demonstrate that the model accounts for the basic phenomenology of the social judgment theory, and allows to study various phenomena such as cognitive dissonance and boomerang effect. The model also displays the order of presentation effect-when consecutively exposed to two opinions, the preference is given to the last opinion (recency) or the first opinion (primacy) -and relates recency to confirmation bias. Finally, we study the model in the case of repeated persuasion and analyze its convergence properties.

Conclusions: The standard Bayesian approach to probabilistic opinion revision is inadequate for describing the observed phenomenology of persuasion process. The simple non-Bayesian model proposed here does agree with this phenomenology and is capable of reproducing a spectrum of effects observed in psychology: primacy-recency phenomenon, boomerang effect and cognitive dissonance. We point out several limitations of the model that should motivate its future development.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Opinions described via Gaussian densities (17).
The initial opinion of formula image is described by Gaussian probability density p(x) (blue curve) centered at zero; see (17). The opinion of formula image amounts to Gaussian probability density q(x) (purple curve) centered at a positive value. For all three figures continuous density f(x) (formula image) were approximated by 100 points formula image, formula image. The resulting opinion formula image of formula image is given by (16) with formula image (olive curve). (a) The opinion of formula image moves towards that of formula image; formula image, formula image, formula image, formula image. (b) The maximally probable opinion of formula image is reinforced; formula image, formula image, formula image, formula image. (c) The change of the opinion of formula image is relatively small provided that the Gaussian densities overlap only in the region of non-commitment; cf. (18), (19). Whenever the densities overlap only within the rejection range the difference between p(x) and formula image is not visible by eyes. For example, if p(x) and q(x) are Gaussian with, respectively, formula image, formula image, formula image, the Hellinger distance (see (30) for definition) formula image is close to maximally far, while the opinion change is small: formula image.
Figure 2
Figure 2. Opinions described via bump densities (28).
Blue curve: the initial opinion of formula image given by (28) with b  =  1. Purple curve: the opinion of formula image described by (28) with formula image. Olive curve: the resulting opinion of formula image obtained via (16) with formula image.
Figure 3
Figure 3. Opinion change versus discrepancy.
(a) The opinion change is quantified via the Hellinger distance formula image between the old and new opinion of formula image (blue curves); see (30) for the definition. For comparison we also include the total variance distance formula image (purple curves); see (33). These two distances are plotted versus the discrepancy formula image. The initial opinion of the agent formula image is Gaussian with formula image and formula image; see (17). The opinion of formula image is Gaussian with formula image and formula image. Thus m quantifies the initial distance between the opinions of formula image and formula image. The final opinion formula image is given by (13). Different curves correspond to different formula image. Blue curves: formula image for formula image (upper curve) and formula image (lower curve). Purple curves: formula image for formula image (upper curve) and formula image (lower curve). The maximum of h(m) (formula image) is reached at formula image (formula image). (b) formula image (formula image) is the point where h(m) (formula image) achieves its maximum as a function of m. Blues points: formula image versus formula image for same parameters as in (a). formula image grows both for formula image and formula image, e.g. formula image, formula image, formula image, formula image. Purple points: formula image versus formula image for same parameters as in (a). (c) The difference of the anchors (maximally probable values) formula image versus formula image for the initial opinions of formula image and formula image given by (17) under formula image, formula image, formula image and formula image. The final opinion formula image of formula image (and its maximally probable value formula image) if found from (13) under formula image (black points), formula image (blue points) and formula image (red points).
Figure 4
Figure 4. Order of presentation effect.
Blue curve: The initial opinion of formula image is described by Gaussian probability density p(x) with formula image and formula image; see (17). Purple (resp. olive) curve: the initial opinion of formula image (resp. formula image) are given by (17) with formula image (resp. formula image) and formula image (resp. formula image). Green curve: the resulting opinion of formula image after interacting first with formula image and then with formula image. Both interactions use formula image. The final opinion of formula image is inclined to the most recent opinion (that of formula image) both with respect to its maximally probable value and distance. The final opinion of formula image has a larger width than the initial one.
Figure 5
Figure 5. Cognitive dissonance.
(a) Blue (resp. purple) curve: the initial opinion of agent formula image (resp. formula image) described by probability density p(x) (resp. q(x)). Olive curve: the final opinion formula image of formula image as given by (16) with formula image. Here p(x) and q(x) are defined by (17) with formula image, formula image, formula image, formula image. The final opinion develops two peaks of comparable height (cognitive dissonance). (b) Avoiding the cognitive dissonance due to a larger formula image: the second peak is much smaller (other parameters are those of (a)). (c) Avoiding the cognitive dissonance due to a smaller formula image: the first peak is much smaller (other parameters are those of (a)).
Figure 6
Figure 6. Opinion change in the boomerang regime.
Blue (resp. purple) curve: the initial opinion of agent formula image (resp. formula image) described by probability density p(x) (resp. q(x)). Olive curve: the final opinion formula image of formula image given by (16) with formula image. Here p(x) and q(x) are given by (17) with formula image and formula image. The anchor (maximally probable opinion) of formula image not only moves away from the anchor of formula image; but it is also enhanced: the (biggest) peak of formula image is larger than that of p(x). The second (smaller) peak of formula image arises because the initial probability of formula image located to the right from the anchor formula image of formula image, moves away from formula image; formula image gets a local minimum close to formula image.
Figure 7
Figure 7. Order of presentation effect in the boomerang regime.
The same as in Fig. 4 but for formula image (boomerang regime). Now the final opinion of formula image is inclined to the first opinion (that of formula image) with respect to the distance. The initial maximally probable opinion of formula image is still maximally probable. Moreover, its probability has increased and the width around it has decreased. The final opinion has 3 peaks.
Figure 8
Figure 8. Illustration of the order of presentation effect in the boomerang regime.
formula image given by (50, 51) versus formula image.
Figure 9
Figure 9. Repeated persuasion in the boomerang regime.
Blue (resp. purple) curve: the initial opinion of agent formula image (resp. formula image) described by probability density p(x) (resp. q(x)) as given by (17) with formula image, formula image, formula image. Olive curve: the opinion of formula image after 50 iterations (52) with formula image.

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