Default effect (psychology)

Among the set of options that agents choose from, the default option is the option the chooser will obtain if he or she does nothing. Less conservative interpretations of default options include options that are normative or suggested. Experiments and observational studies show that making an option a default increases the likelihood that it is chosen; this is called the default effect. Different causes for this effect have been discussed. Setting or changing defaults therefore has been proposed as an effective way of influencing behavior—for example, with respect to deciding whether to become an organ donor, giving consent to receive e-mail marketing, or choosing the level of one’s retirement contributions.

In a choice context, a default refers to that option which choosers end up with if they do not make an active choice. This notion is similar to the one in computer science where defaults are settings or values that are automatically assigned outside of user intervention. Setting the default affects how likely people end up with an option. This is called the default effect. More precisely, it refers to changes in the probability that an agent chooses a particular option when it is set as a default as opposed to the situation where this option has not been set as default. For example, different countries have different rules on how to become an organ donor. In countries with the opt-in policy, all citizens are automatically considered as non-donors unless they actively register as donors. In countries with the opt-out policy, all citizens are automatically considered as donors unless they actively seek to be struck from the register. It has been argued that this difference in policy is the main cause of the significant difference in donor rates across the respective countries.

Some default effects are implied by the situation. In social settings, for example, the normative choice (what others are doing) may be adopted unconsciously as a social default effect. People are thus more likely to choose what they observe other choosing, even if they do not believe that other person is the more knowledgable person. People are also more likely to treat choices that require less justification as defaults. The default option for parole hearings, for example, is to deny prisoners parole.

A number of different explanations have been offered for how default setting causes a change in the choice distribution. These include Cognitive Effort, Switching Costs, Loss Aversion, Recommendation and Change of Meaning.

If an agent is indifferent or conflicted between options, it may involve too much cognitive effort to base a choice on explicit evaluations. In that case, he or she might disregard the evaluations and choose according to the default heuristic instead, which simply states “if there is a default, do nothing about it”. Evidence supporting this cognitive effort account is provided in the realm of social default effects. Participants distracted by a demanding concurrent task were more likely to choose the one of two snacks that they saw a previous participant choose. Increasing the number of snacks received as a function of the choice decreased this social default effect.

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