I need a task which can measure verbal also visual working memory. I am not going to run the test, this is just for theoretical interest. Which tests can be used in this research?
Conway et al. (2005) gives a really nice overview of tasks to measure working memory capacity (WMC). I would refer to that publication for details about the tasks. I'll summarize two tasks below that are related to your question.
Verbal Working Memory. A classic way to measure verbal working memory is a reading span task. The task involves presenting sentences to a subject who makes a judgment about whether the sentence is coherent or not. The subject must also remember some key word (e.g. the last word) in the sentence. The subject reads several such sentences, and then has to recall all of the key words in order. The more sentences that the subject can read, the higher their verbal working memory.
Visual Working Memory Visual/spatial working memory can be tested in a similar way, but with spatial stimuli instead of sentences. One such task is a rotation-span task. In this task, you see a rotated letter, like this:
You have to make a judgment about whether the letter is in the correct orientation (if it were upright, would it be normal or flipped?). After you do that, you then see something like this:
You have to remember what direction the arrow was pointing. You then repeat the process several times, alternating between letters and arrows, until you are asked to recall the order of orientations for all the arrows you saw.