Toyota is designing safety technology that will react to the driver's mood and adjust how the car behaves when faced with a hazard.
The technology decides if the driver is sad, happy, angry or neutral, before assessing how distracted they are likely to be as a result. It can then intervene with safety reminders if required.
Toyota's research suggests an angry or upset driver is less alert to hazards such as a child stepping out in the road, or stationary traffic ahead. In these circumstances, the system would sound an alert sooner than if the driver was considered to have a neutral expression.
Toyota's prototype technology uses a camera to identify facial emotions by taking readings from 238 points on the drivers face. The multiple readings allow the system to function even if the subject is wearing sunglasses or sporting a beard.
The car maker has been working on the technology since 2006, but is yet to offer a firm date for when mood-reading systems could make it to production.
Jonas Ambeck, Toyota's senior manager advanced technology, said: 'The current, basic research should be complete within two to three years, so some of the elements could start to be available in around six years time. For non-vital applications some basic things could be available earlier though."
Ambeck added that the technology could be combined with future mobile phones, and also be used for tasks such as saving power by lighting up the sat-nav only when the driver looks at it.