Sentiment Defenition

joel91482 I am not 100% certain but I would imagine it uses Microsofts Text Analytics API's Sentiment Analysis feature. You can find out more about it here:

https://docs.microsoft.com/en-us/azure/cognitive-services/text-analytics/how-tos/text-analytics-how-to-sentiment-analysis?tabs=version-2

You don't say if you are Forms or Forms Pro, but in FP it was recently added to where you could determine WHICH of your text questions would be used in the sentiment analysis on a survey response. Previously it would read ALL of the questions including things like First Name, Last Name and Email. 

Here is some of the text from the link I shared above that might be of interest.  

The Text Analytics API uses a machine learning classification algorithm to generate a sentiment score between 0 and 1. Scores closer to 1 indicate positive sentiment, while scores closer to 0 indicate negative sentiment. Sentiment analysis is performed on the entire document, instead of individual entities in the text. This means sentiment scores are returned at a document or sentence level.

The model used is pre-trained with an extensive corpus of text and sentiment associations. It utilizes a combination of techniques for analysis, including text processing, part-of-speech analysis, word placement, and word associations. For more information about the algorithm, see https://blogs.technet.microsoft.com/machinelearning/2015/04/08/introducing-text-analytics-in-the-azure-ml-marketplace/. Currently, it isn't possible to provide your own training data.