The short version here is that the field of mathematics is having some trouble getting girls on board for the big win. There have been a number of studies devoted to the subject, but the answer is blunt: girls think that they aren't any good at math (whether they are or not) starting in middle school. You know what they say: "Whether you think you can, or you think you can't: you're right". Shortly after this time, test scores plummet. Later, girls become somewhat rare in the Science, Technology, Engineering, and Mathematics (STEM) fields. Ideally, we can improve these test scores by using an Intelligent Tutoring System (ITS).
One of the core concepts in ITS development is the idea that people can get into a 'zone' where they are learning. Hopefully you can sucker/bribe them into it and trap them. This is usually an extension of the groundbreaking discoveries that "people don't learn well when they are tired" and "Little Timmy is angry right now, and won't sit still". If you had a real tutor sitting in front of this person, they would try to calm the student down. If the student is frustrated with a certain type of problem, you can switch problems. If the student is learning a concept well, you let them. Computer-based tutors are going to have to tackle the same issues.
Presumably, affective tutoring is better than non-affective and tutoring someone is better than not*, and there are a couple of challenges to managing student emotional state:
1 - Computers don't understand emotions
2 - People don't understand emotions
3 - People that program computers don't understand emotions
4 - It's not clear what the most beneficial response to "I hate math!" is for a math tutor (even when the emotion is clear).
Remember the little picture from the problem paragraph? Yea, it's a little cartoon character that studies with you. That's a pedagogical agent.
So, we don't know how people actually feel (emotional state), but we can ask them! Then, when they say that they are anxious, we can make the cartoon anxious too. This way the learners can feel like there is someone suffering along with them. It's cheap, but it works.
So here is the big question that all of that background built up to: Do boys/girls prefer boys/girls for their learning buddy? We'll test some with each and some without.
This paper did not inform on whether students performed better with or without a cartoon character (see Empathetic Pedagogical Agents by Arroyo, cartoons help) but had a rather important finding (below). Girls who study with a girl character think that they are worse at math than when they started (they aren't, they tested better). However, girls who study with a boy character think that they are better.
Why do you care?
First, given that the character is a cartoon, and that they say the same thing, it is a bit surprising to find that there is even a statistical preference. Also, even if there is a preference, the idea that the preference would affect self opinion, regardless of actual performance, is surprising. Finally, if you have a daughter, make sure her tutor or study-partner is a boy.
* - Some studies show that you just want answers. Here.