The strong correlations between “altruistic” and the two REI dimensions may be just artifacts of people’s different inclinations to answer Likert scales with extreme or moderate values.
I don’t think that would explain it, actually. The correlation tests whether a person’s rationality average is a good predictor of their altruism average, on expectation. If the person is biased towards choosing extreme values, then a high rationality average becomes less informative about the expected value of the altruism average, because there’s more variance in that person’s answers.
(I’m not sure I’ve explained this well, but if you disagree, try giving an example of a data-generating model where there is no real correlation between A and B, but a correlation appears in the data because some people are disproportionately likely to choose extreme answers. I’m fairly sure this isn’t possible.)
I don’t think that would explain it, actually. The correlation tests whether a person’s rationality average is a good predictor of their altruism average, on expectation. If the person is biased towards choosing extreme values, then a high rationality average becomes less informative about the expected value of the altruism average, because there’s more variance in that person’s answers.
(I’m not sure I’ve explained this well, but if you disagree, try giving an example of a data-generating model where there is no real correlation between A and B, but a correlation appears in the data because some people are disproportionately likely to choose extreme answers. I’m fairly sure this isn’t possible.)