Avatars vs real pictures for blogs?

I've seen very few successful blogs that have avatars (cartoon pictures) as their author profile picture.

Most of the really successful blogs have pictures of a real person, whether that be themselves or some other random person's picture.

Does having an avatar affect conversion rates, trust, or anything else like that on a blog?

Are there any articles or sources about this subject?

I've read that some people just use stock images of people too. Not sure what to think about that.

I think in general a real person gives the site more credibility. Stock images in my opinion look cheesy.

A profile image can indeed affect click through rate. I agree with the previous poster that a picture of a real person will make the blog more trustworthy, especially if we're talking about professional blogs.

Here are some articles (sorry, I can't yet include links) you can check out:

1. Can Changing Your Profile Picture Manipulate Google Authorship? on The Fresh Egg blog
2. What Profile Photo Works Best on LinkedIn: A Real-Life Experiment.
3. How Optimizing My Ugly Google+ Pic Increased Free Traffic 35% on Moz
4. A Picture is Worth a 42% increase in Click Through Rate on Vero
5. New Research Study Breaks Down "The Perfect Profile Photo"

However, one cannot say there is one perfect avatar type. Much depends on the audience and content. If you are, for instance, a manga artist, your audience will be totally fine with a manga drawing of yourself or something of sorts. It's all relative.