+Mark Traphagen, I have to disagree a bit. There has been so much research done establishing a hard-wired affinity for detection of faces and it being an establishment of trust. Google uses this in their own results (
http://screencast.com/t/XGfF5wICnz5) to establish immediate reinforcement of a correct response. Where does your eye go?
From Susan Weinchenk: "Although the visual cortex is huge and takes up significant brain resources, there is a special part of the brain outside the visual cortex whose sole purpose is to recognize faces. Identified by Nancy Kanwisher (1997), the fusiform face area (FFA) allows faces to bypass the brain's usual interpretive channels and helps us identify them more quickly than objects. The FFA is also near the amygdala, the brain's emotional center."
It is almost impossible for us to do a definitive test. There is so much variation in serps with each page load, logged in or out, not to mention the variation that has been happening in the utilization of the authorship photo in the last many months.
If you look at this page here:
http://screencast.com/t/B8LS2VYgV, you will see that for a search of "lawyers in raleigh, nc" there is only one organic listing above the fold in competition with 10 paid, directory listings, and map. One chance to get a visitors attention out of 11. Now look at:
http://screencast.com/t/na8d07Kdhy. A difference?
We have a lot of data on this but nothing formally released. We emphasize the importance of high-quality photos with each client, because we get feedback from our client's clients that they made a determination to hire the attorney because he/she looked like someone I could trust. They thin-sliced them.
Now for anyone that has read Malcom Gladwell's book, Blink, there can be a negative to this as given by the Warren Harding error.
What if the same rationale was made for the elimination of star ratings in the local listing because there was no "definitive effect on CTR" and they cluttered up the results. After working with a client for a year to gain 5-10 reviews by telling them that the stars draw the eye and also demonstrate social proof for the visitor, you would feel pretty bad and look pretty bad to the client.
I know that there is much less work overhead in authorship markup, but really, the only reason anyone implemented it was because of the image. Google even showed it off in their Rich Snippets tool.
I guess it would be nice to see actual data behind decisions like this when we are asked to spend time and money to implement the Google's suggestions. I also want to note that "Our experiments indicate that click-through behavior on this new less-cluttered design is similar to the previous one" doesn't denote the context of the CTR change. For the serp listing page in aggregate, or for an A/B test between 2 listings in the same position with the photo and without.
Sorry for the long post. I really respect
+John Mueller and we are really lucky to have him share information with us. He goes out of his way to answer questions and is very responsive on G+ whenever anyone needs it. It just seems like authorship was one of the only ways to stand out in the serp noise and now it is gone, and now I have to waste time explaining to clients that there was really no reason for it.