We know Google uses alternative text, alt tags, in images for helping them understand what is an image is about. Google uses it for ranking images. But does Google also use the title attribute in an image?
Here is a picture of the source code difference:
John Mueller of Google responded to the question on Twitter implying the title attribute most likely won't do anything for your image rankings. Here is the tweet:
@dawnieando If you're changing the title with onmouseover, I doubt we'd pick that up. If it's just the title attribute: maybe. Test & tell?— John Mueller (@JohnMu) March 29, 2016
Back in 2008, John Mueller said in regards to the title attribute in images, "feel free to supplement the "alt" attribute with "title" and other attributes if they provide value to your users!" Matt Cutts back in 2008 also mentioned in briefly at the end of one of his old webmaster videos.
In short, it seems title attributes do not play into account with image rankings but that is Google's word. Test it yourself.
Forum discussion at Twitter.
Update: Dawn tested this and guess what, Google does index it, see Google Does Index & Rank Images Title Attribute Tags.