I did an exploratory factor analysis of four measures. First, I constrained the four measures to load on a single factor(eigenvalue: 2.14, % of variance: 53.4 ). Second, the four measures were allowed to load on two factors (eigenvalue and % of variance for the first factor respectively: 2.14, 53.4; and the second factor 1.018, 25.451). Surprisingly, these two methods yielded the same eigenvalue and % of variance for the first factor. However, when I read the Amstrong & Kats (2010) paper, I found that they used the same methods, and had different eigenvalue and % of variance for the one factor and two factor method. Just wondering are my results normal, or I missed something? I appreciate any clue about this. Thank you in advance!
the paper I mentioned: Armstrong, T., & Katz, C. (2010). Further evidence on the discriminant validity of perceptual incivilities measures.