As Waymo deploys more driverless cars to 15 U.S. cities and counting, its vehicles keep encountering new and unexpected situations that they have no script to handle.

Minutes after four top researchers said they were leaving, Google said that Demis Hassabis, the Nobel-winning scientist who led the company’s A.I. lab, was stepping into a new job.

Amazon joined a procession of tech giants that ramped up their spending on artificial intelligence, as its capital expenditures soared 69 percent. Concerns over the industry’s spending are mounting.

Google’s parent company, which has spent heavily on artificial intelligence, also showed growth across its businesses, particularly in cloud computing.