How to configure the double click behavior in an X terminal?

Under different Unix/Linux systems I've observed different double click behavior in X terminal applications (e.g. xterm). Sometimes a double click selects everything left and right until the next non-alphabetic character (e.g. it selects the word under the cursor). Sometimes everything until the next blank/eol is selected (e.g. full paths under the cursor are selected). How can I configure the double click behavior - say - in xterm (because it is available on most systems)? Currently, I find the 2nd mode more convenient for most use cases.