Learning emotion!

As a project, I thought I try to see if my assistant could learn, or at least understand to some extent emotions.

I currently have 2 word arrays, Positive and Negative.
When the user inputs a response to "How do you feel?" the input will be scanned with the two word lists.

For each Positive word found, a variable (emotion) is + 1, and for every Negative word found, its -1.

I've used this method to get a scale of -10 to +10. of which I can form a response depending on the number.

I've been trying to work on responses for each number, but giving an appropriate response for the scale can be a challenge.

But using this, means that my assistant could learn what mood I'm in depending on the input I give.

Further improvements could be multiple random responses depending on the scale.

This is to say each scale will have multiple possible responses but it'll give a random response.

What responses do you think could be appropriate?