Jains believe that mind is an organ of apprehension of all objects of all the sense organs of all the three periods of time, i.e. past, present and future. It is not just in the head, but pervades all over the body.
It is called anindriya (quasi sense) as it is like a sense but is not a sense organ in actual fact. It is an organ of cognition, but not cognizant of all objects as it would imply that mind cognizes the soul which is not the case. Only soul has the capacity to cognize itself without any instrument.
The main utility of mind is to know and feel. Kasayas (passions) are related to the mind.
Within the Jain biological evolution, only a particular segment of 5-sensed beings have a mind, called Samjni. All other living beings are Asamjni (without mind).
References:
1. Internet
2. Jain Vishva Bharati Ladnun Jainology & Comparative Religions Course
Apologies for any unintentional errors in the above post.
