Researchers previously thought that different processes in the brain were subject to separate bottlenecks. For example, the process of reading a map might be limited by a very different mechanism than the act of evaluating ideas and forming opinions. However, new research in PNAS suggests that a "unified" bottleneck may restrict our ability to perform very different cognitive processes simultaneously.
Four different parts of the brain—the bilateral insula, the left interior frontal junction, the anterior superior medial frontal cortex, and the left intraparietal sulcus—were identified as parts of the bottleneck that decreased performance on this dual task.
Not for long mind you, but it wouldn't surprise me if their response time shattered the standard participants.