How can consciousness be defined?
What is the neural basis of subjective experience, cognition, wakefulness, alertness, arousal, and attention?
Quantum mind: Does quantum mechanical phenomena, such as entanglement and superposition, play an important part in the brain's function and can it explain critical aspects of consciousness?
Is there a "hard problem of consciousness"?
What, if any, is the function of consciousness?
What is the nature and mechanism behind near-death experiences?
Problem of representation: How exactly does the mind function (or how does the brain interpret and represent information about the world)?
Controversy: infant language acquisition/first-language acquisition. How are infants able to learn language? One line of debate is between two points of view: that of psychological nativism, i.e., the language ability is somehow "hardwired" in the human brain, and usage based theories of language, according to which language emerges through to brain's interaction with environment and activated by general dispositions for social interaction and communication, abstract symbolic thought and pattern recognition and inference.
Is the human ability to use syntax based on innate mental structures or is syntactic speech the function of intelligence and interaction with other humans? The question is closely related to those of language emergence and acquisition.
Is there a language acquisition device: How localized is language in the brain? Is there a particular area in the brain responsible for the development of language abilities or is it only partially localized?
What fundamental reasons explain why ultimate attainment in second-language acquisition is typically some way short of the native speaker's ability, with learners varying widely in performance?
What are the optimal ways to achieve successful second-language acquisition?
Animals and language: How much human language can animals be taught to use? How much of animal communication can be said to have the same properties as human language (e.g. compositionality of bird calls as syntax)?
What role does linguistic intuition play, how is it formed and how does it function? Is it closely linked to exposure to a unique set of different experiences and their contexts throughout one's personal life?