Intelligence and Emotion in Ageing 177 



is to estimate the relationship of the tasks (or the combination 

 of them) to various criteria that sensible people would suggest. 

 It is obvious that if speedy behaviour is the criterion, the tasks 

 must include some measure of quickness. Other criteria, 

 however, such as the highest level of thought a person can 

 perform, require the consideration of tasks that will enable 

 the appraisal of the level of thinking that the individual can 

 do successfully. Neither criterion is sufficient; others must be 

 considered. Nor should a test be rejected because it gives 

 a fair estimate of one and not of others. The interpretation 

 of mental test results depends upon their affiliations with 

 criteria of success in adult life. 



The scores derived from mental tests involving some 

 sampling of tasks is arbitrary. The weights assigned to these 

 tasks are either based on the judgment of experts, or on their 

 relation to some outside criterion, usually another test of 

 intelligence, or on a combination of judgment and validation. 

 The sum, therefore, of the credits is arbitrary to the degree that 

 the criterion does not fully reflect the variety of intellectual 

 performances that adult life requires. In a sense, then, tasks 

 involving speed, perception, thought and performance lead 

 to an undifferentiated mixture predictive of some kind of 

 average ability if these aspects are positively related. They 

 may fail even in that, if, let us say speed and thought are 

 negatively related. Furthermore, the nature of the score is 

 such that the zero of whatever ability is being estimated is 

 not known. Thus scores cannot be added, subtracted, divided, 

 or multiplied meaningfully. Of course, such scores can be 

 scaled to indicate the likelihood of that much ability in refer- 

 ence to some standard population. But again, the standard 

 population must be clearly defined. Too frequently the 

 standard (or norming) population is an ad hoc group that 

 would take the test. 



The appraisal of intellectual behaviour further suffers in 

 another way. There is considerable uncertainty as to the 

 process by which the person achieves a successful performance. 

 To the same item, a child or a youth or an adult or a senile 



