Eye-tracking - This method lets you measure visual attention, but not impact or value of content. There are remote vendors, but there’s usually a high rate of data loss due to lighting and head orientation requirements - meaning you may recruit 50 people to get 25-30 good pieces of data. In some cases, marrying eye-tracking to Immersion can be useful, but eye-tracking is usually costly and takes a lot of time for data return.
Facial coding - Popularized by the work of psychologist Paul Ekman, facial coding is one of the most widely utilized measures in neuromarketing. This is mostly due to the simplicity of the measure (facial gestures = emotions) and the scalability of using webcams to capture data and algorithms to code facial gestures. However, the latest science (example here) highlights the many flaws of facial coding, including issues with how it’s done but also its lack of predictive validity. Moreover, the technology is almost entirely focused on presenting content via a computer in an environment with sufficient lighting where the subject is asked to remain still and keep their head in one position within a few feet of the camera. Not sure about you, but that is not how we consume any type of content in the real world.
EEG - There’s a ton of variance in quality of tools used to measure EEG. Devices with only a few electrodes, while easy to use, are not reliable or very valid; and medical-grade EEG caps are cumbersome, uncomfortable to wear, and restrained to a lab setting - which of course undermines natural consumer reactions. Some EEG vendors claim they can tease out different emotional responses, but this isn’t possible given the poor spatial resolution of EEG, deep brain location of emotion, and the lack of distinct physiologic patterns for most emotions. Moreover, the cost and expertise make it prohibitive in many real-world applications. Imagine the looks you would get when going into a store wearing a shower cap with electrodes...
Skin conductance / heart rate - Even though we start with cardiac data, we do not measure traditional biometrics. Biometrics is a catch-all term to describe any measure of body responses (e.g., heart rate, skin conductivity/ GSR). Biometrics data are usually output in raw form and are difficult to interpret. The Immersion platform does not provide users raw data like most neuroscience technologies. Moreover, GSR is dependent on tight control of the environment (little hand movement, temperatures around 68-72F).
Implicit reaction time - It is a stretch to identify this as a true neuro methodology. Reaction time is the speed of response and assumes that when things are more strongly associated in the brain, it leads to faster responses. This concept is rooted in academic work on biases, and has not shown reliability or predictive validity in the space of market research.