Is red special? There’s a big literature on this, but

An old post salvaged from the dying Google+:

Is red special? There’s a big literature on this, but I haven’t seen any studies investigate this with quality methodology.

A number of studies purport to investigate whether the color red is special, like whether “red test materials lower performance”. Two problems: 1) these studies may be impossible to replicate because the authors tend not to report the colors in a device-independent fashion! 2) I fail to see how you can compare a single red (or even two or three) to a single green or blue and then conclude something general about red, e.g. “red things are easier to remember”.

We made this point in a recent critical commentary on a particular offending paper: https://f1000research.com/articles/5-1778/v1

Below I’ve pasted bits of some reviews I’ve had to write explaining these issues in more detail, in the hope future studies will improve their methodology:

This is a typical psychology manuscript on color in that it makes the usual mistakes, primarily mistakes associated with not specifying the colors in a device-independent fashion. The cornerstone of science is (supposedly) replicability, and for a study to be replicable the critical characteristics of the stimuli must be reported. This manuscript, like many others in cognitive and social psychology, reports colors in such a way that one could only replicate the colors if one had the exact equipment (monitors) that were used in this study. That is, the colors are reported as RGB coordinates Ordinarily I would recommend rejection for this because it means the manuscript did not meet the PLoS ONE criterion of “3. Experiments, statistics, and other analyses are performed to a high technical standard and are described in sufficient detail.” For some sorts of studies, I think it is somewhat appropriate to let this slide, because most studies aren’t actually making claims about particular colors but rather just choosing various colors whose values aren’t critical. However in this case the study is actually about color!

A general point about papers that study putative effects like the difference between red and other colors is that it may be folly to compare one particular red to one particular green and one particular white as this study did and then claim that you showed something about the difference between red and green! There are hundreds of reds and hundreds of greens. Why would one think that comparing a particular red to a particular green would generalize to all such pairs, or even all the other close-to-focal or unique reds and greens? To establish a claim like that “red decreases performance” rather than “Red with CIE x,y decreases performance relative to use of green CIE x,y” seems to me to require testing of a lot of reds and a lot of greens.

Another unfortunate aspect of the effect reporting here that I frequently see in psychology manuscripts is the use of only noise (random variance)-scaled effect sizes. These measures, scaled by the noise in the experiment, were primarily designed for areas where the meaning of an absolute change in test scores is unknown. For a score on a standardized test, getting a certain absolute score lower or higher actually has a somewhat-known meaning. If psychology is ever to be cumulative, it should use these absolute numbers rather than reporting only numbers that are scaled by the haphazard error variance that happened to have occurred in that particular experiment with that particular population. The reason is that you may have more noise in your study because of more distractible participants or more heterogenous population of participants, and this would reduce the size of the noise-scaled effect size. The main thing of interest should be what you are actually measuring, actual difference in scores, not difference in scores divided by variance that includes things like general heterogeneity of the groups.

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