Shakespeare's Act 1, Scene 1 portrays very many attributes of human nature. Below are listed a couple to use as an example to help you find further attributes.
The first attribute of human nature that Shakespeare reveals is humanities' tendency to follow along like sheep. We first meet Lord Capulet's servants, Sampson and Gregory, while they are bantering back and forth about attacking any of Montagues' men should they see any. Gregory points out that the feud is between their masters and only involves them because they are their master's servants. We see this in Gregory's line, "The quarrel is between our masters and us their men" (17). Hence, even though neither Gregory nor Sampson actually hold the beliefs that are causing the feud, they will still fight Montagues, simply because Lord Capulet has a quarrel with Lord Montague. If these two servants, like all humanity, were not so willing to follow their leader like sheep, a great deal of blood would have been spared from being lost.
Another attribute of human nature that Shakespeare demonstrates in this scene is mankind's common failure to misinterpret situations due to either an irrational mind, blind hatred, and even prejudice. We see this demonstration of human nature in Tybalt's response to Benvolio's drawn sword. Benvolio had drawn his sword to put an end to the servants' fight, saying "Part fools...You know not what you do" (59-60). Tybalt allowed his prejudice, hatred, and irrational mind to interpret Benvolio as challenging innocent servants and challenged him in return. It was Tybalt's poor decision that led to the entire city starting a riot.