ABSTRACT
Investigations of performance and mechanical tests tend to yield very diverse results owing to the effects of background, age, training, etc. Much work has been done in the Services, as well as among children. This shows that g usually plays a large part, except in the more unreliable performance tests and in mechanical assembly tests. In general, performance tests measure the same g + k factors as paper-and-pencil spatial tests, while mechanical tests measure these factors and a mechanical information or experience group factor. Thus, apart from their greater attractiveness, practical or manipulative tests show little or no advantage over paper-and-pencil tests. Additional minor group factors are indicated among special types of performance tests, and within the field of mechanical information.
