Measured as the difference between the score of the items on the two occasions. It would also be possible to calculate the difference in the dimensions and amount of crnge between different groups such as the younger early advocates of environmental protection and their older opposites. Unfortunately such a longitudinal study has not been initiated at the beginning of the transition 10-15 years ago. It could, however, be simulated if the ERI was given twice to each subject, a first time to register the present environmental attitudes, and a second time to elicit memories of past attitudes.