The Sense-Mind, called Manas in yogic psychological terminology, is the mental organ of perception. Western psychology has recognized that the sense organs of touch, smell, taste, hearing and sight deliver impulses to the mind, and it is the conversion of these impulses into an organized sense-awareness of the external world that is undertaken in the mind that gives us actual awareness. It is Manas that carries out this organizing function of awareness of the outer world. Western psychology has, to a great degree, limited this awareness to impulses delivered through the nervous system by the organs of sense, but yogic psychology also allows for a direct perception by the sense-mind beyond or outside the specific impulses carried by the outer organs through this nervous system. This entire system is the result of the evolution of involved consciousness out of Matter and its development into higher ranges of awareness through the action of the vital life energy and the development of a mental consciousness. Human beings share the basic sense-mind capacity with the animals for the most part.
Sri Aurobindo observes, with respect to Manas: “it is a first organising of the crude stuff of the consciousness excited and aroused by external contacts…. What we are physically is a soul asleep in matter which has evolved to the partial wakefulness of a living body pervaded by a crude stuff of external consciousness more or less alive and attentive to the outward impacts of the external world in which we are developing our conscious being. In the animal this stuff of externalised consciousness organises itself into a well-regulated mental sense or organ of perceiving and acting mind. Sense is in fact the mental contact of the embodied consciousness with its surroundings. This contact is always essentially a mental phenomenon; but in fact it depends chiefly upon the development of certain physical organs of contact with objects and with their properties to whose images it is able by habit to give their mental values. What we call the physical senses have a double element, the physical-nervous impression of the object and the mental-nervous value we give to it, and the two together make up our seeing, hearing, smell, taste, touch with all those varieties of sensation of which they, and the touch chiefly, are the starting-point or first transmitting agency. But the Manas is able to receive sense impressions and draw results from them by a direct transmission not dependent on the physical organ. This is more distinct in the lower creation. Man, though he has really a greater capacity for this direct sense, the sixth sense in the mind, has let it fall into abeyance by an exclusive reliance on the physical senses supplemented by the activity of the Buddhi.”
Sri Aurobindo, The Synthesis of Yoga, Part Four: The Yoga of Self-Perfection, Chapter 7, Purification–Intelligence and Will, pp. 636-637