Brain-computer interface technology currently involves implanting electrodes, but Facebook wants to use optical imaging to eliminate the need for invasive surgery, according to Dugan.

Facebook is looking at creating a "silent-speech interface" based on non-invasive sensors that could be made in quantity.

"We are not talking about decoding your random thoughts; that is more than many of us want to know," Dugan quipped.

"We are talking about thoughts you want to share. Words you have decided to send to the speech center of the brain."

Such technology could let people fire off text messages or emails by thinking, instead of needing to interrupt what they are doing to use smartphone touchscreens, for example.

It would also have the potential to capture concepts and semantics associated with words people are thinking, making language differences irrelevant by enabling sharing of what is in mind, Dugan said.

The Building 8 group is also working on sensors that let people "hear" through their skin, with what they feel being converted into words in a variation on how the ear turns vibrations into comprehensible sounds.

"Our brains have the ability to construct language from components," Dugan said.

"I suggest that one day, not so far away, it may be possible for me to think in Mandarin and for you to feel it instantly in Spanish."