What is the default display field for the results list?

I can't seem to figure out how Geocortex decides what field value should be shown for the results list when nothing is specified in the layer settings. Sometimes it also has shows the layer list with a comma and then a field value. But I can't see a pattern here. I'd like to figure out how to force it to show the layer name and use a specific field without specifying one by one in every layer, since we'll often have quite a few layers.