1. Lack of Articulatory Complexity:
- Unlike words, interjections often lack complex articulation patterns. They are usually short, single-syllable sounds produced with minimal effort.
- The sounds themselves are often simple, relying on basic vowel and consonant combinations.
2. Non-Syntactic Structure:
- Interjections do not typically follow the grammatical rules of language. They are often inserted into sentences without being integrated into the syntactic structure.
- They lack clear grammatical function or relationship to other words in the sentence.
3. Emotional Expression:
- Interjections are primarily used to express immediate emotions, such as pain, surprise, or joy. They are not used to convey information or communicate complex ideas.
- This focus on emotional expression suggests a more primitive form of communication, potentially predating the development of complex language.
4. Cross-Linguistic Variation:
- While some interjections are universal, many are language-specific and reflect cultural differences in emotional expression.
- This suggests that interjections are not necessarily innate or fundamental to human language, but rather learned and culturally influenced.
5. Historical Development:
- The origins of interjections are often unclear and may have evolved from non-linguistic vocalizations.
- This suggests that they may have developed independently of the complex grammatical and semantic systems of human language.
In conclusion:
While interjections are part of human speech, they lack the complex articulation, syntactic structure, and information-carrying capacity of traditional language. They are considered unlikely sources of human speech sounds because they are primarily emotional expressions, have unclear origins, and vary significantly across cultures.