An Indian city is set to deploy facial recognition in a bid to detect the expressions of women being harassed in public spaces, eliciting concern among digital rights advocates.

Then there’s an issue of detecting emotions. Data suggests that AI systems have hugely inconsistent track records when it comes to identifying the emotions behind a facial expression.

Researchers at UC Berkeley and Google used machine-learning technology known as a “deep neural network” to analyze facial expressions in some 6 million video clips uploaded to YouTube from people in ...