Unlike the EEG the near-infrared spectroscopy (NIRS) is a relatively new technology. Using infrared light to which the surface of the head and the skull is transparent, the oxygen saturation of the blood on the surface of the brain and thus the activity of the cerebral cortex can be measured. The temporal resolution is much lower, but the measurement method is easier to use than the measurement of an EEG. Moreover, the process is very similar to the measurement of brain activity in magnetic resonance imaging, a popular but extremely complex process in the field of neuromarketing.
Since eyetrackers also work with infrared light, sufficient shielding is necessary in the combination of both methods to prevent interference resulting in artifacts in the NIRS signal.
Significance for the emotional intensity: relatively high
Informative value on the kind of emotion: low
Informative value on the mental workload: medium
Effort: measurements through optical sensors on the scalp surface