¥All the techniques discussed have an underlying objective of dimension
reduction and all use covariance or correlation
matrices. There is often a desire to physically
interpret the new dimensions – this can be
controversial
–For example, oblique rotation is advocated by some because Ôphysical modesÕ
(NB different meaning of ÔmodeÕ) are often
correlated. Other techniques are advocated (independent
component analysis – ICA; Aires et al., 2000) on the
premise that ÔmodesÕ are not just uncorrelated, but
independent