The US workplace is divided into two main categories — high-wage occupations associated with social-cognitive skills such as complex problem solving, and low-wage occupations aligned with sensory-physical skills such as equipment maintenance, according to a new study published in the July 18 issue of Science Advances.

The study also concludes that transitioning from low-income to high-income occupations is difficult because the skills associated with each type of job are so different. This polarization of skills has notable consequences for wages and provides important insights into the controversial "hollowing" of the American middle class, brought about by the relative decrease in middle-wage jobs in the American workplace, authors of the analysis said.

Iyad Rahwan, an author of the paper from Massachusetts Institute of Technology's Media Lab, was surprised to find that workplace skills are highly polarized. "There are two dense clusters of skills … [and] the transition between these two clusters is not smooth. Rather, there is only a narrow bridge of generic skills connecting the two clusters," he said.