Technology firms should do more to connect people in positive ways and steer away from trends that have tended to exploit human weaknesses, ethicists told a meeting of Silicon Valley leaders on Tuesday.

Tristan Harris and Aza Raskin are the co-founders of the nonprofit Center for Humane Technology and the ones who prompted Apple and Google to nudge phone users toward reducing their screen time.

Now they want companies and regulators to focus on reversing what they called "human downgrading," which they see as at the root of a dozen worsening problems, by reconsidering the design and financial incentives of their systems.

Before a hand-picked crowd of about 300 technologists, philanthropists and others concerned with issues such as internet addiction, political polarization, and the spread of misinformation on the web, Harris said Silicon Valley was too focused on making computers surpass human strengths, rather than worrying about how they already exploit human weaknesses.

If that is not reversed, he said, "that could be the end of human agency," or free will. Problems include the spread of hate speech and conspiracy theories, propelled by financial incentives to keep users engaged alongside the use of powerful artificial intelligence on platforms like Alphabet Inc's YouTube, Harris said.

YouTube and other companies have said they are cracking down on extremist speech and have removed advertising revenue-sharing from some categories of content.

Active Facebook communities can be a force for good but they also aid the dissemination of false information, the campaigners said. For example, a vocal fringe that oppose vaccines, believing contrary to scientific evidence that they cause autism, has led to an uptick in diseases that were nearly eradicated.

Facebook said in March it would reduce the distribution of content from groups promoting vaccine hoaxes. In an interview after his speech, Harris said that what he has called a race to the bottom of the brainstem – manipulation of human instincts and emotions – could be reversed.

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For example, he said that Apple and Google could reward app developers who help users, or Facebook could suggest that someone showing signs of depression call a friend who had previously been supportive.

Tech personalities attending included Apple co-founder Steve Wozniak, early Facebook funder turned critic Roger McNamee and MoveOn founders Joan Blades and Wes Boyd. Tech money is also backing the Center, including charitable funds started by founders of Hewlett Packard, EBay, and Craigslist. The big companies, Harris said, "can change the incentives." (VOA)