As I've pointed out previously, open-plan offices are the dumbest management fad of all time. However, while I knew OPOs were stupid, I didn't realize that they were actually making organizations stupid by reducing the collective intelligence of the workers inside them.

Open-plan offices were intended to increase an organization's collective intelligence by creating more opportunities for face-to-face interaction. In theory, this made perfect sense. Removing cubicle walls meant seeing more faces of more co-workers, which should obviously increase face-to-face interaction. More collaboration means an organization that's nimbler and more innovative.

However, according to a detailed Harvard study entitled "The Impact of the 'Open' Workspace on Human Collaboration," the introduction of an open-plan environment in two Fortune 500 companies reduced face-to-face interaction by 70 percent. Rather than communicate face-to-face, workers in such an environment used email and texting more frequently than when they worked in a less transparent environment.

Unfortunately, email and texting are not nearly as effective as face-to-face at creating collaboration. Furthermore, open plan increased social influence (because you can see what everyone else is doing), which made the organization less effective because

... richness in social information was detrimental to collective intelligence outcomes, with performance being best when social learning opportunities were constrained [because] intermittent rather than constant social influence produced the best performance among humans collectively engaged in complex problem solving.

Turns out that having everyone in the same room causes employees talk to one another less frequently but email more frequently, while simultaneously creating social pressure for everyone to "look busy." By contrast, more privacy created more face-to-face interactions, less emailing, and more creativity because each worker can moderate his or her own cycle of downtime versus creativity.

Ironically, open-plan offices don't just drive workers to use email and text more frequently to avoid disturbing co-workers. It also pushes workers away from using other online communication tools, like videoconferencing, which simulate face-to-face interaction and are therefore more effective at creating collaboration and thus increasing collective intelligence.

In other words, even if open-plan offices didn't decrease productivity (which they do, as shown by the Harvard study and dozens of others), they're not really cost effective, because while they can reduce floor space rental costs, they make your organization dumber than if you just let everyone work from home.