Last week Microsoft Corp. said it would stop selling software that guesses a person¡¯s mood by looking at their face.

The reason: It could be discriminatory. Computer vision software, which is used in self-driving cars and facial recognition, has long had issues with errors that come at the expense of women and people of color. Microsoft¡¯s decision to halt the system entirely is one way of dealing with the problem.

But there¡¯s another, novel approach that tech firms are exploring: training AI on ¡°synthetic¡± images to make it less biased.