Final answer:
Emily Dickinson is the author who developed a new style of poetry to write about complex thoughts full of meaning, offering innovative techniques that anticipated Modernism.
Step-by-step explanation:
The author who developed a new style of poetry to express complex thoughts full of meaning is D. Emily Dickinson. Emily Dickinson and Walt Whitman both established new voices in American literature by breaking from traditional forms. Dickinson, through her unique and concise lyrical poetry, offered a fresh perspective on familiar landscapes and themes. Her technical complexity and innovative techniques anticipated the Modernist movement. Whitman, on the other hand, embraced free verse and celebrated the common language in his poetry, most notably in 'Song of Myself', which is considered one of the most influential poems in American literature.