A lot of research has been conducted to understand the underlying speech processes that occur within the mind of persons who were born deaf.
There are mainly two core primary areas of the brain affected by hearing loss – the temporal lobe and the left hemisphere. The functions of these two parts of the brain heavily influence the thought processing capacity of the mind.
Studies have shown that humans generally engage in thought processes by linking words together, or through images, or a combination of both.

The temporal lobe helps to process sound and the left hemisphere is fundamental in transforming thoughts to speech. However, this two vital areas are heavily affected in the event of deafness.
While persons with normal hearing can understand spoken words, studies have shown that the same function works in “sign language” for deaf people. In other words, they understand signs perfectly in same manner as if it were spoken in words. This means that people who were born with a hearing loss primarily think in images and signs.

However, this may be different for people who used to hear spoken words before losing the ability to hear.
It is pertinent to note that there is no single specific sign language which all persons with hearing loss can subscribe to. Records show that sign languages differ by geographic location.