THEORIES OF SENSORY MOTOR FUNCTIONS IN ANCIENT INDIAN SCRIPTURES

                      The contribution of ancient Indian scriptures to the field of psychology has not been just restricted to personality or psychological intervention processes. There are more significant contributions to  basic domains of psychology, which has not been explored and understood. Cognitive psychology is one such area. Clear and distinctive explanations related to normal sensory motor functions are available in various scripts and this the knowledge is not just restricted to Para-psychological areas such as ESP, telepathy, precognition and psychokineses which is usually seen as the contribution of ancient Indian systems.

                The details of many modern illustrations which is described as explanations by psychologists of 18^th and 19^th century, related to this topic is available in various scriptures of ancient Indian origin. But these facts do not find any place in the books on basic psychology, not even a reference.  The one major reason may be that most of these books have been written by western authors and even the ones by Indian authors have strongly dependent on these books. The in-depth knowledge of sensation and perception available in these scriptures a valuable source which needs to be incorporated in all sources of learning related to basic psychology.

                 One of the basic source of information on sensory motor functions is the transcripts by Charaka and Susruta the patrons of Indian medical system. Even though they regarded heart as the seat of consciousness (may be because the immediate impact of every sensation brings about a change in rate of heart beat), they had a clear conception of the sensory nerves (manovaha nadi) and the motor nerves (ajnavaha nadi).

                 But the Tantric writers who regarded brain as the seat of consciousness have not only distinguished between the sensory nerves and the motor nerves, but also recognized different kinds of sensory nerves : the olfactory nerves (gandhavaha nadl) the optic nerves (ritfawha nadi) the auditory nerves, (sabdauaha nadi), the gustatory nerves, (rasavaha nadi) and the tactile nerves (sparsavaha nadi).

                 The scriptures of Buddhism divided the five sense organs eye, ear, nose, tounge and skin in to two types, the prapyakari (recognizing objects when they come in direct contact with them) and aprapyakari (recognizing  objects at a distance). They also added Consciousness as a sense organ because it can recognize and understand non-sensuous objects beyond what is done by the other five sense organs.

                 The Jainism scripts divides the sense organs in to two types the objective senses (dravyendriya – physical sense organs ) and subjective senses (bhavendriya – physical correlates). But according to them except eyes All the other sense-organs are prapyakari because they come in direct contact with their objects, the only difference is that  the direct contact may be gross (sthula) or subtle (suksma). The organs of touch and taste come in contact with gross objects. But the organs of smell and hearing come in contact with subtle objects. The olfactory organ has direct contact with minute particles of the object smelt. The auditory organ has direct contact with merely a kind of motion of agitation (sound waves) developed  by contact of one physical object against another. But with regard to eyes they still maintained it as aprapyakari may be because the knowledge related to light ways on dependency of visual sensations on reflections of light from an object was not explored

            According to the Samkhya philosophy the sense organs, are classified in to two – the external and the internal.  It further divides the external sense-organs into two classes: organs of cognition / knowledge (buddhmdriya) and organs of action (karmendriya). The visual organ, the auditory organ, the olfactory organ, the gustatory organ, and the tactual organ are the organs of cognition. The vocal organ, the grasping organ, the locomotive organ, the evacuative organ, and the generative organ are the organs of action. The internal organs are the  mind (manas) which by itself constitutes the attitude and emotions, the intelligence (buddhi)  and ego (ahamkara).  By the buddhmdriyas the Samkhya does not refer to the physical organs but, the determinate sensory psychophysical impulses which go out to the external objects and receive impressions from them, and by the karmendriyas it means the determinate motor psychophysical impulses which react to the objects perceived. The five organs of buddhmdriyas, the five karmendriyas, and the three internal organs manas buddhi and ahamkara together enable wholistic sensory-motor function.  The distinction between the organs of knowledge and the organs of action is ultimately based upon the primary distinction between the sensory and motor mechanisms of the psychophysical organism, by which it knows the external world and reacts to it.

                       The Samkhya holds that all sense-organs are prapyakarl ; they move out to their objects , take in their forms., and apprehend them. The sense-organs cannot apprehend their objects without being related to them in some way or other. If the sense-organs  apprehend their objects without being related to  them, then they may apprehend all objects, distant and hidden which is not seen as a normal process. The sense-organs are conceived as moving out to their objects and assuming their forms without leaving connection with the body. And this is possible only by means of a peculiar modification of the senses called vrtti. It is the modifications or vrtti that connects the senses with their objects. The vrtti is neither a part not a quality of the senses. If it were a part it would not be able to bring about the connection of the sensory organs with distant objects. These facts correlates to the theory of absolute threshold and Just Noticeable Difference (JND) which is described as the minimum amount of energy or change required to activate the sensory process.

                       The detailed description of sensory motor process also throws more light into the sensory analysis and sensory coding which is described in modern psychology as the process of changing important features of the world into messages understood by the brain.