I can see how the brain vs. brawn distinction could be pernicious, because mechanical robots can do one thing, but a robot that's smart like a human can do anything. Something about that formulation feels like an oversimplification though.

We've had technology replace mental labor before too.[0]

Spreadsheets democratized accounting and while making the work easier, also put a tax prep firm on every corner in the US. It vastly increased the number of people performing some sort of accounting. Some are small business owners that do it themselves, and can now hire a few extra employees.

We've had AI that can write beautiful music for ages, now it can duplicate the style of any composer,[1] but we largely don't care and still have pop stars. And composers.

The work Taylor Swift does for her millions of dollars probably involves layers of cultivating a story about a real person, responding correctly to paparazzi in different scenarios, and judging when to capitalize on interactions on Twitter between other celebrities. This probably sounds like I'm saying she's calculating, but really it has to be an enormous amount of instinct, because it's all probably not reducible to any series of tasks that can be enumerated or even perhaps knowable. Several people have tried to analyze her success, I'm not sure anyone actually understands it.[2][3]

More important for ordinary employees, we still have people compose film scores for some reason. Maybe because even if you can emulate other composers, someone has to decide which composer to emulate, which means having some ability to guess at another artist's as yet unexpressed artistic vision. Once you have the decades of training and experience to do all that, might as well write the thing yourself. Maybe recommendation engines could get there, but I'm not sure those work with novel creations, and I'm not sure we're even interested in perfecting those anymore for areas where they're proven (more or less) to work.[4]

Maybe the weird thing about mental assistants is that they expand the workforce, rather than reducing it. Robots are set up to run automatically, but all the AI we develop is driven by humans to solve day to day problems.

It's like if instead of robotics we built programmable exoskeletons or mechs. The number of employees would explode. There'd still be people building everything, inside the machines. That's what we're doing with computers in a lot of fields. Software is most often like a suit our brain wears to think faster or more reliably.

On the other hand, there are also examples of muscle jobs that haven't yet been perfectly replaced.[5]

The lack of a sewing robot (or ubiquitous clothes folding robots as another commenter mentioned) illustrates that we tend to overgeneralize. Some brawn problems are easy, and some are hard. Same for brain problems. Some problems will stick around, either stubbornly unable to be mechanized, or just not worth the cost.

Also, feedback systems kick in to ensure that labor force participation bounces between reasonable extremes. A lot of the recent downturn in the LFPR can be attributed to retirees.[6] It seems to be leveling off or even heading up again, but regardless the US rate remains well within historical norms.[7]

Sorry this turned out super long and rambly.

[0] http://www.npr.org/sections/money/2015/02/25/389027988/episo...

[1] http://newatlas.com/creative-artificial-intelligence-compute...

[2] https://blog.longreads.com/2014/07/07/taylor-swift-is-a-musi...

[3] http://www.gq.com/story/taylor-swift-gq-cover-story?currentP...

[4] http://www.slashfilm.com/happened-netflixs-recommendation-en...

[5] http://www.npr.org/sections/money/2016/08/03/488611449/episo...

[6] http://www.bloomberg.com/news/articles/2015-01-19/why-labor-...

[7] http://data.bls.gov/generated_files/graphics/latest_numbers_...

I can't seem to export the BLS page I generated. Basically fully expand the range of this page to see the entire history: http://data.bls.gov/timeseries/LNS11300000