Confronted by the militancy of longshore unions, port operators have deployed automation, in part to limit their vulnerability to labor troubles. Not coincidentally, dockworkers tend to look suspiciously at robots and other forms of innovation, divining threats to their livelihoods.

At least 25,000 dockworkers at East and Gulf Coast ports could walk off the job next week, impacting about half of the country's imports and possibly sending prices higher for consumers. Negotiations between the workers' union and the employers face a Tuesday deadline.