We see very little of the humans and Piccolo training on Kaio-sama's planet. It's entirely possible that they did try and failed.
My Tumblr. Currently side-by-side liveblogging Digimon Adventure, sub vs dub.I like to believe that, after they came back to life, Yamcha finally got it down but kept it to himself because he knew nobody would believe him and it wouldn't matter anyway.
edited 3rd Jun '15 10:35:36 AM by TobiasDrake
My Tumblr. Currently side-by-side liveblogging Digimon Adventure, sub vs dub.Maybe they did learn it,but Goku kept going on about how they stole his techniques.
Meanwhile, in a parallel universe, Yamcha was absorbed by Super Buu. Buu tried to shake it off, but his battle power began to drop at an astonishing rate. Yamcha was fighting Majin Buu from within: he'd triggered the Kaioken and was ramping up the multiplier, amplifying the effects his negative battle power had on Buu. As he hit x10, Super Buu fell helpless to his knees and Goku was able to defeat him with one swift kick.
My Tumblr. Currently side-by-side liveblogging Digimon Adventure, sub vs dub.How do you know that works?
Chiaozu was doing a Nuzlocke run, so he died.
edited 3rd Jun '15 12:09:07 PM by KnownUnknown
Didn't we do this yesterday?
Anyway, I'd say probably? They retained enough memory to want Gero dead for what he did to them. It's impossible to say for sure, of course. In DBZA, I'd say the answer is definitely, what with them referring to their parents and all that.
...Calling them by their birth names is a bit weird to me, actually. I keep thinking of a different Lapis all together.
I have a message from another time...I asked, you didn't answer.
And, well. It didn't seem like they knew in the original series. Especially since they still go by 17 and 18.
...And, I mean. Sometimes people forget different parts of things.
Especially with regards to trauma.
...I mean, their eyes flash red at one point, so. Gero put things in their heads.

Yeah, the Kaioken is incredibly difficult to learn and use. Even Kaio-sama can't actually perform the technique.
My Tumblr. Currently side-by-side liveblogging Digimon Adventure, sub vs dub.