Neuroscience and psychology have explained a great deal, yet some of the most basic questions about the mind remain open. “Mystery” here does not mean something supernatural. It means a question without an agreed scientific answer. This article tries to say clearly which parts are well established and which are not.
Consciousness
What is known. Researchers can study which brain activity goes along with a person reporting that they saw or felt something. Experiments comparing what people consciously notice with what they do not have shown that a lot of processing takes place outside awareness. Damage to certain brain regions, anesthesia and sleep all change or remove consciousness in predictable ways, which strongly suggests the brain is deeply involved.
What is not known. Why any of this brain activity is accompanied by subjective experience, the feeling of what it is like to see red or taste coffee, is unexplained. Philosophers sometimes call this the “hard problem” of consciousness. Several scientific theories exist, including ones centered on information broadcast widely across the brain, on integration of information, or on the brain’s predictions about itself. None has won general agreement, and researchers actively test them against each other. There is also no widely accepted test that could confirm consciousness in, say, a newborn, an unresponsive patient, an animal or a machine, which keeps these questions under debate, including the question of whether machine thinking could ever involve experience.
Memory
What is known. Memory is not one thing. Short-term or working memory holds a small amount of information for seconds; long-term memory can last for decades. Learning appears to involve changes in the strength of connections between neurons, and a structure called the hippocampus is important for forming new memories of events. The broader process is covered in our piece on memory formation.
What is not known. Exactly how a memory is physically stored is still being worked out, including how a specific memory is spread across many cells, and how it is kept stable over years while cells and molecules turn over. Another point of ongoing study is the reliability of memory. Research on recall shows that remembering is reconstructive: each retrieval can alter a memory, and vivid, confident memories can still be inaccurate. Confidence is not a reliable guide to accuracy. Why we forget, and how much forgetting is a loss versus a useful cleanup, is also debated.
Perception
What is known. What we perceive is not a direct recording of the world. The brain combines signals from the eyes, ears and other organs with expectations from past experience. Optical illusions work because the brain’s inferences, normally helpful, can be fooled. The human senses are the starting point of this process, but most of the work happens afterward in the brain.
What is not known. How the brain binds separate features, such as color, shape, motion and sound, into one coherent experience is not fully understood. Nor is it settled how much of perception is driven by incoming data versus prediction; “predictive” accounts are influential but still debated. Whether two people experience the same color in the same way is not something we can currently check, since we can compare reports and behavior but not experiences themselves.
Dreams, thought and the sense of self
Other puzzles are connected. Scientists continue to compare dream theories, with no single account explaining why we dream. The sense of being a unified self, with a continuing identity and a feeling of making free choices, is also under study. Experiments in which brain activity can be detected shortly before a person reports deciding to move have been taken by some as a challenge to free will, but their interpretation is disputed, and most researchers caution against sweeping conclusions from them.
Inner speech and mental imagery vary notably between people. Some report vivid pictures in the mind’s eye, others very little, and many people only discover how different their experiences are as adults. This variation is a reminder that we have limited access to each other’s minds.
Why these questions are hard
Several reasons recur:
- The mind is private. Researchers depend largely on what people say and do, and self-reports can be unreliable.
- The brain is enormously complex, with billions of cells and far more connections, and the way neuron signals combine into thoughts is only partly mapped.
- Correlation is easier to find than explanation. Seeing that a region is active during a task does not by itself show how it produces the experience or behavior.
- Concepts like “consciousness” are used in several different senses, so people sometimes argue past each other.
How to read claims about the mind
Be cautious with headlines that say science has “found” the seat of the soul, “solved” consciousness, or proved that free will is an illusion. Such statements usually go well beyond the experiment. A reasonable stance is to treat established findings as solid, treat leading theories as hypotheses under test, and be comfortable saying “we do not yet know.”
None of this is a reason for pessimism. Many questions that seemed unanswerable, such as how nerves carry signals, were eventually explained. Whether the hardest ones will yield in the same way is itself an open question.