Editing Group polarization (section)

=== Empirical findings ===
Since the late 1960s, psychologists have carried out a number of studies on various aspects of attitude polarization.

In 1979, [[Charles Lord]], [[Lee Ross]] and [[Mark Lepper]]<ref name=lordrosslepper/> performed a study in which they selected two groups of people, one group strongly in favor of [[capital punishment]], the other strongly opposed. The researchers initially measured the strength with which people held their position. Later, both the pro- and anti-capital punishment people were put into small groups and shown one of two cards, each containing a statement about the results of a research project written on it. For example:<blockquote>Kroner and Phillips (1977) compared murder rates for the year before and the year after adoption of capital punishment in 14 states. In 11 of the 14 states, murder rates were lower after adoption of the death penalty. This research supports the deterrent effect of the death penalty.{{sfn|Lord|Ross|Lepper|1979|p=2100}}</blockquote>or:<blockquote>Palmer and Crandall (1977) compared murder rates in 10 pairs of neighboring states with different capital punishment laws. In 8 of the 10 pairs, murder rates were higher in the state with capital punishment. This research opposes the deterrent effect of the death penalty.{{sfn|Lord|Ross|Lepper|1979|p=2100}}</blockquote>The researchers again asked people about the strength of their beliefs about the [[deterrence (penology)|deterrence]] effect of the death penalty, and, this time, also asked them about the effect that the research had had on their attitudes.

In the next stage of the research, the participants were given more information about the study described on the card they received, including details of the research, critiques of the research, and the researchers' responses to those critiques. The participants' degree of commitment to their original positions were re-measured, and the participants were asked about the quality of the research and the effect the research had on their beliefs. Finally, the trial was rerun on all participants using a card that supported the opposite position to that they had initially seen.

The researchers found that people tended to believe that research that supported their original views had been better conducted and was more convincing than research that didn't.{{sfn|Lord|Ross|Lepper|1979|pp=2102, 2105-6}} Whichever position they held initially, people tended to hold that position more strongly after reading research that supported it. Lord ''et al.'' point out that it is reasonable for people to be less critical of research that supports their current position, but it seems less rational for people to significantly increase the strength of their attitudes when they read supporting evidence.{{sfn|Lord|Ross|Lepper|1979|pp=2106-7}} When people had read both the research that supported their views and the research that did not, they tended to hold their original attitudes ''more'' strongly than before they received that information.{{sfn|Lord|Ross|Lepper|1979|pp=2105-6}} These results should be understood in the context of several problems in the implementation of the study, including the fact the researchers changed the scaling of the outcome of the variable, so measuring attitude change was impossible, and measured polarization using a subjective assessment of attitude change and not a direct measure of how much change had occurred.{{sfn|Lord|Ross|Lepper|1979|p=2101n1}}