Suppose a worker went out of her way to help the boss complete a project on time. Some of her co-workers saw that behavior and thought she was...

There are many possible reasons for these differing interpretations. The two that come most immediately to mind are history and projection. 

First, the track record of this person's actions is bound to sway the opinions of co-workers.  This might be a person who helps only the boss and is otherwise a poor team player.  That would tend to cause people to interpret her actions as meant only to curry favor with management. On the other hand, if this person has the deserved reputation as being helpful with everyone, the interpretation is more likely to be that she is simply a good team player. 

Second, we tend to judge other peoples' actions by thinking about what we would do in similar circumstances. This is a form of projection, meaning we project onto others our own thoughts and feelings.  A person whose usual motive for helping is to curry favor with someone is likely to project that idea onto this worker, believing that she has the same motivations.  But someone who wants to be a good helper to all is going to project that attitude onto this worker, feeling that she is similarly motivated. 

For either explanation, it is important to realize how our perceptions can be so easily influenced. They can be influenced by history, and they can just as easily be skewed by our own thoughts and feelings.  It makes it difficult to know sometimes what, exactly, is "truth." This helpful worker is performing the same actions, no matter how they are perceived.  Perhaps that is the only truth one can take away.