It has been roughly four decades since industrial robots - with mechanical arms that can be programmed to weld, paint and pick up and place objects with monotonous regularity - first began to transform assembly lines in Europe, Japan and the U.S. Yet walk the floor of any manufacturer, from metal shops to electronics factories, and you might be surprised by how many tasks are still performed by human hands - even some that could be done by machines.

The largest U.S. retailers reported strong online sales in their second-quarter earnings reports recently, extending a trend that has seen e-commerce revenue expand far faster than store sales, and several said they are making strides in delivering goods to consumers more profitably.