MIT spinout Cogito has raised a $4m extension for its series B round, which achieved an initial $15m close in November 2016.

Cogito, a voice-analysis technology developer spun out of Massachusetts Institute of Technology (MIT), has raised a $4m extension for its series B round from unnamed investors, Xconomy reported today.

Cogito previously achieved a $15m close for the round in November 2016 led by OpenView, with participation from Salesforce Ventures, the corporate venturing arm of cloud computing company Salesforce, and Romulus Capital.

Cogito, founded in 2007, has developed analytics software aimed at call centres. The technology analyses voice patterns, such as long pauses, conversation flow and vocal strain, of both staff and callers to offer feedback on how to make discussions more efficient.

The technology is based on research led by Alex Pentland, professor at the MIT Media Lab and professor of media arts and sciences as well as director of the Human Dynamics Laboratory.

The money will be used to acquire more clients and to support further technology development.

Cogito previously secured $1m in capital in May 2016, according to a securities filing. In 2015, Romulus Capital led a $5.5m series A round that also featured Salesforce Ventures.

Cogito had raised $1m in seed capital in 2014, adding to a $20,000 investment as part of its participation in accelerator Summer@Highland in 2007.