According to Lenneberg's findings, what is suggested to exist for language development?

Lenneberg's findings introduce the concept of a critical period for language acquisition, suggesting that there is a specific window of time during which language development occurs most naturally and efficiently. This critical period hypothesis indicates that if language exposure does not happen within this timeframe, the ability to acquire language may be significantly impaired. This notion is supported by observations of children who are not exposed to language during early years, highlighting the importance of timely language input for the natural progression of linguistic skills.

The other options, while relevant to language acquisition, do not capture Lenneberg's primary focus on the time-sensitive nature of learning language. Universal language refers to the idea of a shared structure among all languages, which is different from the timing of language learning. A variety of language inputs is indeed beneficial for development, though it does not highlight the crucial timing aspect that Lenneberg emphasized. Lastly, a system of imitation plays a role in language learning but is not the central thesis of Lenneberg's findings regarding critical developmental periods.