Advertising isn’t cheap — brands are predicted to spend a collective $757.44 billion on advertising by 2021. Understandably, they want a guarantee they’re getting their money’s worth, which is where startups like Spark Neuro come in.

Spark Neuro, a New York-based company founded in 2017, keeps a relatively low profile. But its star-studded lineup of investors includes actor Will Smith, former Disney CEO Michael Eisner, and prolific tech investor Peter Thiel, who along with five other investors today led a $13.5 funding round.

The startup’s secret sauce is an electroencephalogram (EEG) headset that evaluates electrical patterns in the brain. (The “Spark” in Spark Neuro stands for Scientific Persuasive Artistic Research-Driven Knowledge.) Data from it and other devices, including cameras that track gaze and facial expressions and electrodermal sensors, are fed into proprietary algorithms that determine as best they can a person’s emotional state.

“Spark Neuro’s approach to evaluating audience engagement is unique in that it combines brain and other nervous system activity to understand how people react to content accurately,” CEO Spencer Gerrol said in an interview conducted via email. “[Its] sophistication in measuring brain activity is unmatched. What is especially unique is that the data is processed and reported live in real time, requiring a powerhouse complex set of algorithms that clean noise from signal and process raw data into meaningful metrics.”

[VentureBeat’s executive-level Transform event, near SF on August 21 & 22 is all about how to harness AI to grow…