Third Sign (UnControllable Behaviors) Pt. 1

There are many times in the Novel where Lennie's emotions take control over him, and he can't do anything about it.  The first sign where Lennie shows that he has no control over his emotions is when he kills the mouse in his hand.  When he kills the mouse, he explains to George that he squished the head of the mouse because it bit his thumb.  Normally someone would either drop the mouse, or move their hand away from the mouse.  With Lennie's mental health it disables him from thinking about the situation and he let's his emotions control him.  He felt frustrated with the mouse, so with his frustration he squished the head of the mouse and killed it.