How unitary is the capacity-limited attentional focus?

Cowan assumes a unitary capacity-limited attentional focus. We argue that t wo main problems need to be solved before this assumption can complement th eoretical knowledge about human cognition. First, it needs to be clarified what exactly the nature of the elements (chunks) within the attentional foc us is. Second, an elaborated process model needs to be developed and testab le assumptions about the proposed capacity limitation need to be formulated .