The software was originally developed by Emotient to help assess viewer reactions to their ads, but has also been used to look for signs of pain in patients, and even monitor shopper's facial expressions.

However, it is unclear what Apple plans to use the technology for.

'Emotient is the leader in emotion detection and sentiment analysis, part of a neuromarketing wave that is driving a quantum leap in customer understanding,' the firm says on its website.

'Our services quantify emotional response, leading to insights and actions that improves your products and how you market them.'

An Apple spokeswoman confirmed the purchase with the company's standard statement after an acquisition, saying Apple 'buys smaller technology companies from time to time, and we generally do not discuss our purpose or plans.' 

The San Diego firm came under fire last year, when it announced that it had been granted a patent for a method of collecting and labeling as many as 100,000 facial images a day so computers can better recognize different expressions.

Paul Ekman, a psychologist who pioneered the study of reading faces to determine emotions who was an adviser to Emotient, told the Wall Street Journal the technology could reveal people’s emotions without their consent, and their feelings could be misinterpreted.

The company was founded by a team of six PhDs from the University of California, San Diego, who are the foremost experts in applying machine learning, computer vision and cognitive science to facial behavioral analysis. 

The Emotient software processes facial expressions and provides an aggregate emotional read-out, measuring overall sentiment (positive, negative or neutral); primary emotions (joy, surprise, sadness, fear, disgust, contempt and anger); and advanced emotions (frustration and confusion).

One of its first products was designed for Google's Glass.

'Emotient’s Sentiment Analysis Glassware demonstrates our goal to emotion-enable any manner of device and build the next layer of automatic sensors,' said Ken Denman, CEO, Emotient.

'It’s a breakthrough technology that allows companies to aggregate customer sentiment by processing facial expressions anonymously.

'We believe there is broad applicability for this service to improve the customer experience, particularly in retail.'

According to its website, 'the company is at the vanguard of a new wave of emotion analysis that will lead to a quantum leap in customer understanding and emotion-aware computing.'

(dailymail.co.uk)