Multitasking: You can’t pay full attention to both sights and sounds

A recent study on multi-tasking revealed that attention is a zero-sum game. We only have so much attention to give, so dividing it up between visual and auditory stimulus means we’re not giving our full attention to either. The study involved people listening to digits and letters and watching a rapidly changing visual display of digits and letters. I think that might bias the study a bit, as you’re dividing your attention between two similar tasks using different senses. But is our attention as divided when the tasks are different? Because I can handle two different tasks okay, but when they’re similar I lose a lot of concentration because my brain switches between them constantly instead of handling them in parallel.