Complex sentence: As Kuusela and Paul state the thinking aloud protocol can be divided into two different experimental procedures: the first one is the concurrent thinking aloud protocol, collected during the decision task; the second procedure is the retrospective thinking aloud protocol gathered after the decision task.
Split into simpler sentences: As Kuusela and Paul state the think-aloud protocol can be divided into two different experimental procedures. The first one is the concurrent think-aloud protocol, collected during the decision task.