Board Thread:General Discussion/@comment-31621258-20170328203819/@comment-24821641-20170328215925

If you reset/reload after telling Toriel whether you like cinnamon or butterscotch more, she remembers and if you say she guessed right, she says she often feels like she already knows humans that fall. So they could reset, but not to Frisk's extent, they must have given up eventually.

Also, the red soul probably isn't determination - it's always associated with yellow (though that soul's trait is justice), Alphys was able to extract it from all the souls, and the other souls' traits are virtues while determination seems neutral to me.