Before proceeding with this Thought Post I want to be clear about one point: technically speaking, I do not believe that one person motivates another. Rather, I believe motivation is a personal experience, generated by 'self'...not generated by others. I motivate me and you motivate you...and there are some things you can do to help me be self-motivated and there are some things I can do to help you be self-motivated. 

So, the best way to pose the question is: What is it about us that helps other people be self-motivated?

I think the answer boils down to three things I've written about on numerous occasions before: intelligence, self-control, and drive.

These three attributes are the foundations of character.

Yes - I understand we have values and vision and we have goals and, related to these things, we also have rules that we live by. On the other hand these things follow in time and are consequences of our unique combination of intelligence, self-control, and drive. Put another way - when others observe our behaviour they make conscious or unconscious decisions about our character. And our intelligence, our self-control, and our drive are the attributes that determine our behaviour. 

With this logic in mind, I believe other people's motivation is affected by their perception of my character and whether or not my behaviour is consistent and aligned with their perception of my character.

I will continue to use first-person tense to explain:

First, if the person has known me for a period of time then the person will hold a perception of my character. If the person perceives my character to be 'admirable' then my behaviour has a chance to help the person be self-motivated. Conversely, if the person perceives my character to be 'questionable' or worse then my behaviour will have little opportunity to help the person be self-motivated. In effect, the person will shut me out and be prone to experience negative feelings and thoughts when I am present [or in mind]. If the person perceives my character to be 'admirable' and then finds my behaviour inconsistent with that perception, again, my behaviour will have little opportunity to help the person be self-motivated. And, if my behaviour remains inconsistent with the person's perception of my character then the person will adjust his or her perception of my character...i.e., the person will downgrade his or her perception of my character until it matches the perception of my behaviour. And, while this is happening the person will tend to feel less motivated about interacting with me...and that can be described as de-motivating.

When people believe my character is 'questionable' or worse I have little ability to positively influence them. And, they may describe that as 'demotivating'.

When people believe my character is 'admirable' but my behaviour is inconsistent with admirable character I have little ability to positively influence them. And, they may describe that as 'demotivating'.

Only when people believe my character is 'admirable' and my behaviour is consistent with admirable character do I have a chance to positively influence them. And, they may describe that as 'motivating'.

My character and my behaviour can help people feel motivated.

Fortunately, we human beings have the ability to construct and improve both these things.