This is more than likely some type of hardware problem with your mouse or track pad.
When was the last time you restarted your computer?
What type of computer are you using and what pointing device?
This is not something that LR has ever done on it's own. There is no setting in LR for this to happen and the act of selecting anything is controlled by the operating system.
Which version of Lr are you using
When you are in Library using COMPARE view it will automatically select 2 images like your description. As I remember, some past versions of Lr had a bug related to this that would affect other operations.
I've re-booted several times, to no avail. Computer was built by a friend, ASUS motherboard. I've had it about 1 1/2 years & this strange behavior started in the last couple of days. I'm using a Wacom mouse on an Intuos 2 (very old) tablet. I'll mess with the Wacom controls in the Control Panel, maybe re-set to defaults to see if that helps. Thanks for the suggestions.
This is 2015.10.1. The behavior is similar to COMPARE view, except that in COMPARE view the selection of two images is instantaneous when I click on one, whereas my current problem results in the adjacent image also selecting in about one or two seconds after I click on one.
Update the mouse and GPU drivers and test.
Unfortunately, Wacom stopped supporting the Intuos 2 software several years ago. I guess this is just something I'll have to live with. It doesn't really hurt me in the Develop module. I do have to be careful in Library module if I'm changing star rating, Exporting, etc., since it can result in an undesired action to the second image. Oh well, . . .
I've tried a different mouse, updated GPU driver, disabled by third monitor, all to no avail. When I click on any image (Library or Develop modules), the image immediately to the right is selected about 1-2 seconds later. The primary focus remains on the first selected, but this is a real operational problem. I can't delete an image, change star rating, etc. in grid view because the same action will apply to the other image that LR selects. It's somewhat like Compare view in appearance. I remember reading somewhere about setting up to go through a bunch of images so that when you apply something to an image, the focus automatically moves to the next.
Is no one else seeing this problem?
I have never had this happen and IIRC never heard of it before. IMHO this has to be some type of hardware problem. LR simply doesn't ever do that.
1. From your description, it's not entirely clear: Is the selection being extended to include the second photo to the right, with the most-selected photo (with the brighter highlight) staying on the current photo? Or is the current photo getting deselected and the photo to the right getting selected, with it becoming the new most-selected photo?
2. You asked:
I remember reading somewhere about setting up to go through a bunch of images so that when you apply something to an image, the focus automatically moves to the next.
That is the menu command Photo > Auto Advance in Library. From your descriptions so far, it doesn't sound like this is what you're experiencing. But make sure it is unchecked.
3. You can try deleting LR's preferences: https://www.lightroomqueen.com/articles-page/how-do-i-reset-lightrooms-preferences/ . Sprinkling that magic fairy dust often fixes weird behavior.
4. If those steps don't help, then making a screen recording that shows the dynamic behavior could help. Upload it to Dropbox or similar and post the link here. You could also post it to Youtube at HD resolution, though that could make it a little harder to see fine details.
John, thank you so much for the Delete Preferences suggestion; after an hour playing around, that seems to have solved my problem. I'd heard this suggestion in the past but never had a problem before, so had forgotten about it. It seems the problem may have originated with the download of the new 2015.10.1 release last week since the problem only started showing up in the last few days, but I guess I don't care what caused it as long as it's gone. Thanks again.