'Mental telepathy' can be a broad term that encompasses numerous things. It typically means reading the thoughts between people without using normal senses. The difference is a huge between having an intuitive gut feeling and knowing information that could only be gathered by reading somebody's mind. Very basic skills can be construed as mental telepathy but so can very complex. Different levels of mental telepathy can be summarized in this article.
KINESICS COMMUNICATION:
Kinesics, or non-verbal communication, occurs whenever two people communicate without speaking, using their eyes, body language, and facial expressions instead. This can range from simple messages like 'go away' to entire conversations. Any parent who has tried to communicate something to their spouse that they don't want their children to hear has experienced this. Non-verbal communication is achieved easiest and most accurately between people who know each other well—siblings, parents and children, husbands and wives, and close friends.
Some can argue (with good reason) that this doesn't count as mental telepathy, as the two people are using their senses to communicate (just not with sounds). Technically, this is correct. This doesn't mean, however, that mental telepathy does not play a role. The fact that non-verbal communication occurs most successfully between people who are related (like family), or who have lived together for extended periods of time (like spouses) implies that their minds might be more attuned to each other than to strangers. On the other hand, one could argue that this merely means the two people know each other well enough to understand each others more subtle body language, or have created agreed-upon nonverbal signals to communicate.
EMPATHY:
Empathy is the ability to recognize, perceive, or directly experience the emotions of others. Some people are very poor at this, and others are very good at this, being able to mentally 'put themselves in another's shoes' and understand how they must be feeling. Empathy can be increased with training and practice. Actors, for example, are able to imitate the emotions of others, even to the point of being able to make themselves spontaneously laugh or cry.
Most people have experienced 'sympathetic pain'—feeling another person's pain as if it were your own. For example, after witnessing someone close to you break their arm, you may experience an uncomfortable feeling or even an ache in your arm, even though you know it's fine. Similarly, when someone close to you is experiencing an overwhelming emotion, such as joy, grief, or depression, you may feel an echo of the same emotion inside you. Finally, there is the phenomena of long distance empathy. In this case, a person suddenly knows—they FEEL it—that someone close to them is in danger, has been hurt, or is in pain, even though they are not near the person at the time.
There are some skeptics and psychologists who scoff at these kind of incidents and call them the work of an overactive brain. In certain cases they may have a point because we can see the injury and the hurt. However in cases of long distance empathy where a person doesn't even know that his loved one is injured or hurt, then they don't have an explanation about why a person who cannot even see the other person can feel the pain.
SYMBOL AND OBJECT PROJECTION:
There is another kind of telepathy which involves sending and receiving concrete symbols and objects between two people. Here advanced Mental telepathy is involved and it is a phenomena outside the five senses. This kind of mental telepathy involves a lot of training, concentration and practice. There is a receiver and a sender involved in this.
The simpler the concept, the easier it is to communicate through thought alone. For example, a color or shape may be easier to convey than an animal.
Zener cards often used in mental telepathy test are an example of this principle. Simple, concrete black-and-white symbols (a circle, square, star, plus sign, and three wavy lines), gives even a random guess a 20% chance of being right. On the other hand, a shared, known, limited set of concrete symbols may increase the coordination of the thoughts between sender and receiver. A success rate of 50% or higher (which have happened) can not be explained away by simple statistics, but may indicate a level of mental telepathy, instead.
ABSTRACT CONCEPTS
This level of mental telepathy involves more advanced abstract concepts than shapes and colors. Here people communicate ideas, values and actions, which is quite tough the success rate is quite low. Telepaths seldom achieve this level and the ones who do are pretty rare.
Interestingly there are certain animals which can communicate effectively and we have still not discovered their modus operandi. Telepathy may be one of the methods. In this kind of communication between animals very basic abstract concepts will be involved. Since animals do not have prefrontal lobes which enhance complex communication, this communication will be restricted to basic impulses like thirst hunger and even danger.
There is a theory that humans were once capable of telepathy, but lost it as the species evolved and developed language. If this is true, then with the right stimulation humans should be able to 'relearn' this dormant ability.
If enough people can develop these powers, theoretically all humans in the future could use mental telepathy to communicate, according to some scientific beliefs.
