In Chapter Two of Of Mice and Men, how does the boss react to Lennie's silence?

In Chapter Two of Steinbeck's Of Mice and Men, the boss reacts to Lennie's silence with some initial suspicion. George repeatedly answers on Lennie's behalf when the boss questions them about their names and where they've been working, which prompts the boss to ask, "He ain't much of a talker, is he?" George immediately defends Lennie, stating, "No, he ain't, but he's sure a hell of a good worker. Strong as a bull."

Lennie attempts to echo George, which only sends him into a bit of a panic. As George continues to answer for Lennie, the boss gets irritated and suspects that George is manipulating Lennie in some fashion--perhaps acting as his helper in order to steal all of Lennie's wages. George explains that Lennie is not "bright," lying to the man by telling him that Lennie is his cousin who was kicked in the head by a horse as a child. The boss decides to hire them to join the grain team anyway, provided that George not "try to put nothing over."