Hello,
Thank you for your reply.
Yes, you are correct. You still need to use the data in the ‘raw’ columns to re-compute the scaled values with the ‘global’ MIN and MAX.
Regarding EmotivPRO prividing the “final” scaling, this is a good suggestion. We considered it, but it may be confusing for people who recorded specific values of each PM at different times during the live recording. We decided it was better to export the data as originally displayed, but provide a means to rescale it to a more consistent scale.
The correlation between rescaled and raw values is very high. The rescaling formula is logistic, which maps -inf to +inf onto the 0-1 range. Outlying data points are compressed into the top and bottom few percent of the 0-1 scale, while retaining a strict monotonic mapping. That is, if raw(t1) > raw(t2) then rescaled(t1) > rescaled(t2) for all t1, t2
Whether you choose raw or rescaled data depends on the requirements of your analysis. Typically different subjects have widely differing range and and baseline values for the same performance metrics. The differences are due to both physical and psychological differences.
Anatomically, every brain is folded differently. Specific functional areas are not perfectly mapped onto the same regions of each cortex. Many major functions are located in ‘similar’ regions for anatomical or developmental reasons, but no two brains are mapped identically due to fairly chaotic developmental processes. The huge cortical area is densely folded to fit inside the very finite skull volume. Different fold patterns and deep, interlocked folds mean that any specific functional region of the cortical surface may be deeply buried in tissue or presented on the outer surface of the cortex, Differing skull thicknesses, location of muscles, blood vessels etc also contribute to wide variations in scale of different PMs.
Different personalities also express different ranges of emotions and different “operating levels” – think of the difference between an ex-fighter pilot who can calmly land a dead passenger plane on the Hudson River, and a cab driver (we’ve all had one) whose natural state is yelling at the traffic and gets enraged by someone daring to ride a bicycle on a city street.
If the target of your research is to compare between different types of stimulus across a population, it is more appropriate to use standardised data such as the rescaled PMs. If you are more interested in differences between individuals, then (perhaps) raw values are more appropriate.
Hope this helps. If you have other questions, please let me know.
