Tom Stafford writes:
I [Stafford] suggest applying the methods of experimental psychology to a longstanding question in political science.
Many people feel that there is no “real difference” between political parties (for example, Labour vs Conservatives in the UK). Politians are all the same, right? At least superficially, mainsteam parties will all echo commitments to values such as “community” and “education” and positions such as “tough on crime” and “for a strong economy”.
In perceptual psychology we have a number of methods of calculating how accurate and sensitive a sense, like sight or hearing, is. Using these ‘psychophysical’ methods you can come up with a number which allows you to compare across different senses, or across different people. So, for example, we could show that vision is more sensitive than hearing, or that your vision is more sensitive than mine (or even that your vision is more sensitive than my hearing). These methods account for things like base-rate biases in people’s responding (so, for example, it could account for the fact that you might be more likely to say you can see something when you are in doubt, while I might be more likely to say that I can’t when I am in doubt). This sensitivity statistic I am thinking of is called d’ (“d prime”) by psychologists.
I’ve been considering whether these methods from perceptual psychology could be used to address the question of how similar the positions of political parties are. My way of testing and tracking the difference in the stated policy positions of the parties would work like this: you take a standard public expression of party positions (election manifestos?) and sample policy statements (size of sample to be decided, somewhere between individual sentences and paragraphs). Then, after coding the statements for their year and origin, you anonymise them and ask voters to say which party they think the statements come from. With a few psychophysical calculations we can then come up with a sensitivity statistics which reveals how easy voters find it to distinguish the policy positions of the two parties, and we can then compare how this changes over time, or in different policy areas.
Friend and political scientist Will Jennings told me that – of course – political scientists already look at this topic. The British Election Study has been asking voters since 1964 how close the parties are. Projects such as the Comparative Manifestos Project have coded party manifestos from around the world, using techniques such as automated coding of text and expert surveys (i.e. asking academics what they think).
The problem with asking voters how close the parties are, or to code the parties as more “left-wing” or more “right-wing” is that you deal with opinions of voters, not their actual ability to discriminate between the positions of the parties. The problem with coding the manifestos is that it puts a layer of interpretation (as to what counts as left-wing, or conservative, or whatever) before you can judge one manifesto as closer or further away from another.
My psychophysics approach tests directly the ability of voters to discriminate between stated policy positions. We do this by presenting many small fragments of the manifestos and asking a participant to judge which party they are from. By gathering many many judgements we can get a sense of how likely they are to name each particular party (i.e. their bias) and get a sense for how likely they are to be correct (i.e. their sensitivity). We combine these, accounting for any bias towards naming a particular party, to get an estimate of their ability to discriminate between the parties based on their stated policy positions. You can average this index across people, removing random variation in sensitivity between people, to get an estimate of how discriminable two stated positions truly are.
This looks interesting to me..My only comment is that, in the U.S., it’s recognized by political scientists and voters alike that there are real differences between political parties. So, rather than “address the question of how similar the positions of political parties are,” I recommend that you accept ahead of time that the parties are different (at least in the United States; I don’t know enough about England to comment on Labour etc) and study the ways in which the parties are perceived to differ.
Also, in American National Election Study does ask respondents where they think the parties stand on particular issues. The survey does not merely ask voters how close the parties are, or to code the parties as more “left-wing” or more “right-wing.” So a lot of the data you’re looking for has already been gathered. Which is a good thing, since you can’t go back in time to interview voters in previous elections.