2. Introduction to Sign language: modality independence, sign elements and acquisition
Sign language is the principal language of the deaf community. It is a naturally occurring language and it does not follow the pattern and grammar of any spoken language. It evolves within the deaf community and has its independent form and structure. It provides the deaf with the ability to express themselves with ease Kyle and Woll (1985), Senghas (1995), Valli et al (2011), Zeshan (2000).
2.1 The modularity of mind and modality independence
The study of sign language follows from the claim that language instantiation is independent of its modality. According to the hypothesis of “the modularity of mind”, language is a separate module in the brain differentiated
Results showed that the left hemisphere in the brain which controls linguistic abilities (language production and comprehension) in spoken language also regulates sign language processing. “Damage to the left hemisphere produces sign language aphasias that are parallel to spoken language aphasias, while damage to the right hemisphere does not” Emmorey et al (2013: 158). Deaf signers who have lesions in the left frontal cortex exhibit Broca’s aphasia-like symptoms such as effortful signing with reduced grammatical complexity, similar to effortful speech in hearing patients who suffer from Broca’ aphasia. Damage to the left hemisphere also results in poorer sign comprehension. Therefore, the brain is lateralized not only for spoken language but also for sign language. The neural circuits responsible for language functions remain impartial to Language in different
They are produced using hand shape, hand movement and hand orientation and location (place where the hand is placed) which are the formational elements of a sign.

2.2.1. Iconic signs
Iconic signs are mimetic signs which have a one-to-one relation between the sign and the meaning. “Iconic means that the form of the symbol is an icon or representation of some aspect of the thing or activity being symbolized” Valli et al (2011:4). The signer tends to act out an event. Consider the examples below collected by the researcher from ISLH.

1. EAT WRITE

2.2.2. Non- iconic signs
Non- iconic signs do not have a one-to-one relation between the sign and the meaning. They are arbitrary and do not reflect the form of the thing or activity being symbolized.
2. JUMP