Very dated now I am afraid, but it may still apply.... in the early mid- 1990s some of the police attended Cranwell and used their training methods to filter the potential observers prior to police observer training....
APTITUDE TESTING FOR POTENTIAL AIR OBSERVERS
METHODOLOGY
The original aptitude selection model or Police Air Observers was based upon a battery of tests which were used for the recruiting and selection of pilots and air crew for the RAF at Cranwell, Lincolnshire. In effect, the model originally used for selection comprised of five aptitude domains:-
Attention Capability
It is the ability to store information accurately in short term memory and to cope with an environment in which different types of information (visual and auditory) are presented at a fast rate. The greater an individual’s attention capability the more information the individual can hold simultaneously in memory, Greater individual flexibility indicates an ability to cope with switching attention between tasks under pressure of time.
Mental Speed
The ability to perform routine mental tasks quickly and accurately. Tasks may include mental arithmetic, reckoning, checking etc.
Psychomotor
The ability to co-ordinate the hand and eye or the foot and eye. Sometimes called stick skills and can be measured using specific tracking tasks. There are two basic types of tracking task. One involves following a stimulus and is known as an “anticipatory” tracking task. The other involves holding a stimulus (e.g. dot or cross) on target whilst the stimulus is continually pulled away from the target and is known as the “compensatory” tracking task.
Spatial Ability
The ability to form mental pictures and manipulate information in what is sometimes called the “mind’s Eye”. It is related to the ability to construct mental maps and manipulate mental images.
Reasoning
The ability to reason using verbal, numerical or diagrammatic information. The ability to identify patterns in presented information and involves the combined use of sensible rules of thumb and logical approach. It is closely related to problem solving ability or general intelligence.
The Reasoning domain was deliberately excluded from the testing of police air observers as it is not aircrew specific.
Hope that helps without misleading by being 'historical' and imprecise.