Alertness in humans can be determined by many kinds of verbal and non-verbal tests; activity in animals by observation, for example of wheel-running in rodents.

Performance on a battery of non-verbal auditory tests devised by the Medical Research Council's Institute of Hearing Research was found to be heavily influenced by non-sensory task demands, and indices of APD had low reliability when this was controlled for.

This is one reason why experts such as Moore have recommended using non-verbal auditory tests to diagnose APD.

While investigating stroke-patients with damage to the thalamus, Cipolotti et al. (2008) found that the stroke victims had poor recognition and recall memory on verbal and non-verbal tests.

They are non-verbal tests, though there are verbal instructions which had to be translated into sign for deaf participants.

In their study where they carefully matched their bilingual to their monolingual participants, they found that the bilinguals showed significant advantages over the monolinguals in both verbal and non-verbal tests, especially in non-verbal tests that required more mental flexibility.

They administered a set of non-verbal tests that are designed to measure cognitive ability (Raven's Progressive Matrices) to a bilingual sample of children.

An older child can provide answers to both verbal and non-verbal tests to more complex tasks in a more detailed and accurate way and therefore produce more direct data.

Since Matrix Reasoning and Picture Concepts involve the use of visual stimuli and do not require expressive language, they are considered to be non-verbal tests of Gf.