P. Phililips,
You are not going to believe this, but yesterday, they did NOT work independently. I had set the DISPLAY setting to largest text on my iMac. I adjusted the various windows of apps so I could view whole page, etc. Later in the day, I opened my MacBook, began my photoshop app, and the window was blown-up. Couldn't understand why this was the case. Checked settings and found the DISPLAY setting was also set to the largest text. I reset it to the default on Macbook. This morning, I opened iMac and found the DISPLAY setting was also set to DEFAULT-certainly not what I had previously set -- thus, my request for help from the Community. Upon receiving your reply to my question, I opened both my iMac and Macbook, reset each at different text size for DISPLAY, restarted each and now both retained the settings I just made. I know it was Superball Sunday and all, but the DISPLAY settings did not act independently then, but they do now.