Somebody I know was talking about using EEG to measure brain activity while a person imagines that they are driving from one location to another. And while they are imagining this, the person being tested would be asked questions like “How many vowels are there in the word alphabet?”. I think this is called matched tasks? What is the purpose of asking these questions while the person is imagining driving to a certain location?
The hypothesis is that you have different types of active brain regions. For example you have working memory, and emotion.
A matching task “targets” the same “brain regions”, in this case your working memory.
You could also do ‘non matching’ tasks e.g. imagine driving somewhere and asking a subject to think of an emotional moment.
But why they would ask this to a subject really depends on what they are researching.