For every tool in Photoshop's Tool Box, the user may choose to fully reset JUST that tool to its default settings. To do this, look up to the Options Bar. On the far left side you will see a button which displays an icon of the currently selected tool. This is the Tool Preset picker. As indicated by the little down-pointing triangle, if you click once on this button a menu will drop down. In the upper right corner of this dropped menu you will see another little triangle, pointing toward the right. By clicking on this button yet another menu will fly out. By scrolling down the list of commands you will see two entries:

• Reset Tool and
• Reset All Tools

The first thing to try when a tool is not acting like you expect it should is to apply the command "Reset Tool" from this menu. Often this will cure a problem, and by starting your Photoshop troubleshooting with this procedure you aren't resetting Photoshop's entire behavior and environment to factory default in a wholesale manner. Instead, you're just getting that particular tool back to its default settings, leaving the rest of Photoshop's settings alone.

If this doesn't cure the problem you're having, then you may need to move on to deleting/resetting all of your Photoshop preferences to factory default.

Please also see attached graphic.

(Thanks to Len Hewitt and Phos)