Argument Summary: Mark often "refers to the dullness and hardness of heart of the disciples." Matt and Luke often remove this and make the disciples look better. It is easier to understand the harder readings in Mark as original. [Stein, 70]

Once again the argument here is assumed against Mark copying Matt, but what about these two operating independently? Here are some points:

• Constant references to disciple stupidity are more likely to come from an eyewitness doing a dramatic presentation than from an oral didactic core. We can see Peter adding "duh" references when he speaks as an eyewitness who recalls being one of those "duhs" himself. But what good are these sorts of "duhs" loaded into a core that is supposed to be memorized? These would be needless distractions in an Ur-Matthew.
• Matt is hardly missing "duhs" of his own. Historically speaking it is hardly unlikely that Jesus used "duhs" to get the disciples primed. Such methods would shame the disciples and would be used by a teacher in an honor-shame setting. What we see in Matt is that there ARE "duhs" here and there (8:26, 14:31, 16:8-11); they simply are not pounded into us with reckless abandon.
• Some claims of "duh" are just plain paranoid. Hawkins [121] for example thinks Matt would eliminate Mark 5:31's words from the disciples to Jesus "And sayest thou, Who touched me?") because it "may have been thought disrespectful" to Jesus. Aside from presuming motive (how about "surprise" rather than "disrespect"?), this is just plain double-layer mind-reading -- presuming to read the mind of an author, who is presumed to also be mind-reading his potential readers! -- and deserves no credence.

And why should they be? Peter's preaching, an oral presentation, offered a personal challenge, an in-your-face challenge as he preached; what worth would this be in Matthew's written version which could just be put down? Many of these are a function not of Marcan priority, but of Petrine preaching. (Other examples may not be, but individual examples will be dealt with in the texts.)