>> very disturbing. coming up, the man you saw in sarah's piece, tristin harris, who was featured in the social dilemma, and also testified before congress about the dangers of big tech, joins us next. >> the natural function of these platforms is to reward conspiracy theories, outrage what we call the race to the bottom of the brain stem. it's the reason why all of you at home have crazier and crazier constituents who believe crazier and crazier things and you have to respond to them. ♪ hands to the sky, all mine ♪ ♪ woah woah no ceiling woah woah good feeling woah ♪ before we talk about tax-smart investing, what's new? -audrey's expecting... -twins! ♪ we'd be closer to the twins. change in plans. at fidelity, a change in plans is always part of the plan. that was quick. and rewarding.