Long before Mezmer and all western knowledge on hypnosis around the time when Aristotle wrote the Peri Psyches doctors in china knew about the secrets of HsiMenJitsu the asian name for hypnosis and the effect of mental stimulis on the body.  The primary work of saiminjusu(Japanese spelling) was to allow an individual to place themselves into an auto-hypnotic state and then manipulate their sub-conscious mind to varing effects; deadining pain, ignoring exaustion, acelerating physical and mental recovery.  The base system worked quite similarly to self-hypnosis techniques used today.  In more advanced techniques the developement of guided imagery from an experianced doctor (hypnotist) was to develope a gaze and a voice that could sudate the concious mind to allow the doctor to work.  The voice is known to use certain vocal tones that produce frequencies that the human ear cannot detect.  (Barry White actually uses them although subscounciously.)  These techniques allow an inate control over personal internal energy.  The most advansed techniques teach the practitioner how to pick up on and manipulate character flaws.  This system is based on a five elemental religious system(much of the techniques were veiled in abstract terms).
The elements are expained here help you under stand:

Earth:  (chi) the basest grouping of things, shows up as the solid physicality of the body, and is reflected in feelings of stablity and restitance to change or movement.

Water:  (sui) the next higher grouping, is manifest as the fluid aspect of the body, and is reflected in feelings of changablity and emotional reactions to physical changes.

Fire:  (ka) seen as the dynamic energy of agressiveness, and is reflected in feelings of warmth and expanciveness, and the active direction of power and control over one's enviorment.

Wind:  (fu) the highest physical manifestation, displays itself as intelect and love, and is reflected in feelings of wisdom and benevolence, and in concious concideration of one's interactions with others.

Void:  (ku) the emptyness of potential, the source of all that is, gives rise to creative capability and the ability to direct the body's energies to take the form of any of the four lower manifestations.

the system was split into combat usable techniques (flaws), and ways to obtain control out of combat (needs).

Flaws:

    Laziness ::the desire to stay immobile.  Those manipulated through this can be gaurds who give only cusury searches or opponents who won't chase a foe.

     Anger ::short temper.  People manipulated with these techniques can be easily tricked into a reckless rage.  Staying calm while using insults, jabs, and stinging tactics works best.

     Fear ::usualy a lack of self confidence, sometimes others.  Manipulating fearfull people ends the fight with a minimum of injurys.  Threats and intimidation work well against these individuals sometimes stunts or flashy fight manuevers work as well.

    Sympathy ::softheartedness towards others.  By making oneself  look weak or fearfull the sympathetic opponent won't want to harm you and may even help you.

     Vanity ::overwelming feelings of self-importance, and possibly for a cause(a specific martial art style, religion, and the like).  The potential of the void is shown here, through different tactics or circumstances vain people can be placed into different levels of flaws.  Sometimes laziness occures when one belives themself superior to others.  When their belief of superiority is chalenged anger is usualy the result.  By proving them more average then they believed earlier a state of fear is the common result(anger on occaision but it is rare).  And, by feining belief in their illusion a form of sympathy is possibly formed.
 

Needs:

    Security ::Corresponding to the earth level of the personality, is a strong need for some.  Many times ninja cultiveted an accomplice by providing food and protection to a hunted or dispossessed man or family.  Morality and political ideals dim in the importance for many people who are deprived of the fundimental necessities of normal living.  On the other side of the coin, threatening the security of a man might bring him into submission.  (The "I know where you live," threat.)

    Sex ::Another reliable ploy, the desires of an individual can be catered to by supplying sexual excitment, which works on the water level of the personality.  In the midts of lusty physical gratification, an enemy's gaurd is lowered and he becomes much more vulnerable to physical attack or verbal probing.  The use of a female ninja was often resorted to when other measures have failed.

    Wealth ::The Ninja can appeal to the fire level of is targetby taking advantage of his desire for monetary gain. This is an obvious ploy, summed up by the contemporary observation that "Every man has his price."  Paying someone off, or offering him a chance for great wealth, can often be used to inspire at least temporary loyality.

    Pride ::A man's own appraisal of his personal worth or significance in the eyes of others springs from the wind level of consciousness, and results in pride.  Never to be underestimated, pride often causes a man to fight relentlessly against overwelming odds, even to the death, for the sake of self-image or reputation.  The ninja might offer a way to regain lost pride and esteem, or threaten an action that could humiliate a man of prestige, thus bringing him into submission.

    Pleasure ::I order to gain someone's confidence or cooperation, the ninja attacks the creative and expressive level of the void, by discovering and supplying that which brings him pleasure of fulfillment.  Beyond security or even wealth, men still seek more, whether it be power, influence, increased enjoyment in life, answers to ageless questions, or the opportunity for personal expression.