Just wondering, how does science detect a thought?
This is an interesting area of research.
A bit of background may help: The area of the brain associated with thought is the cortex (the outer, convoluted part), especially the frontal cortex (behind the forehead). The cortex contains about 16 billion neurons, the cells that do the brain's work. Each of these connects to about 10,000 neighbouring neurons, so a single cc of cortex contains as many connections as there are stars in our galaxy (200-400 billion). Each neuron can receive signals from other neurons and send signals to others through these connections. The signals are various patterns or bursts of electro-chemical pulses. When a neuron receives a certain number of incoming pulses, it will trigger and 'fire' off its own pulses to neurons down the line.
Thoughts are the synchronised activity of neurons right across the cortex. Recently, a new generation of brain scanners (not unlike hospital MRI scanners) has been able to detect neurons that are active, and image them, so it is possible to track and see the waves of neuron activity sweeping across the cortex in real time, and to correlate patterns and areas of activity with thoughts and sensations. It is already possible to read directly out of the brain what someone is seeing, by scanning the occipital lobe (the visual processing area at the back of the head). For example, if someone is looking at text, a scan of their brain can determine what letters they are seeing.
As for thoughts, it's early days, and there is not yet a general way to translate the neural activity patterns of thought into descriptions of thoughts, but by recording the activity when someone is thinking about or feeling something specific, it is possible to subsequently detect when they are thinking those thoughts again because the patterns of neural activity are similar. So once 'trained', the system can tell what someone is thinking. It is also possible to suppress the activity in a particular part of the cortex, so that certain thoughts or thought patterns are selectively suppressed.
At present, the resolution is low, and these systems must be trained for each individual and their thought patterns, but it is (crudely) possible to detect someone's thoughts, and in specific cases, what they are actually thinking about.
Progress in this area is extremely rapid, and there are all kinds of valuable spin-offs, such as direct thought control of prosthetic limbs, wheelchairs, and computers for the disabled, and potential for detecting and disrupting abnormal thought patterns in people with severe behavioural problems. Imagine being able to forestall severe depressive, manic, or psychotic episodes by recognising the thought patterns associated with their onset, and stimulating the brain so as to prevent the undesired patterns continuing.
Of course there are a lot of moral and ethical questions raised by the growing ability to detect, recognise, and even (possibly) modify thought patterns.