I don't have a scientific answer but I do have one based off personal experience and knowledge.
1. The page title is used for ranking purposes and having a brand appended to every title tag actually results in page titles where Google decides to display the brand first and then the keywords which often times get cut off. So your title can be Bubble Gum 72 oz | Target and Google can/does display it as Target : Bubble Gum 72 oz, now imagine the same scenario with a longer brand name and all the sudden Google is cutting off the keywords/ click worthy title.
2. I think that unless you're a very dominate player in a certain industry your brand name doesn't help, even with that said smaller less "authoritative" brands can out rank older brand by just being a better player in the internet marketing game. Consider your audience, is the brand making them click the page because every other brand is spammy/crap or is the brand not adding value?
I expect that you'll get very similar answers to mine from other here. What I would recommend is removing the brand from the title on decent traffic page (not your best but not your worst) and run a test, see if the brand in title does anything.
Lastly, if you need to have the brand and it's causing issues just throw it into the meta description.