Learners experience emotions in a variety of valence and arousal in learning, which impacts the cognitive process and the success of learning. Learning emotions research has a wide range of benefits from improving learning outcomes and experience in Intelligent Tutoring System (ITS), as well as increasing operation and work productivity. This survey reviews techniques that have been used to measure emotions and theories for modeling emotions. It investigates EEG-based Brain-Computer Interaction (BCI) of general and learning emotion recognition. The induction methods of learning emotions and related issues are also included and discussed. The survey concludes with challenges for further learning emotion research.