Although computational linguistic methods have been applied to spoken and written text, they have only recently been used to study poetry. Here, we examine the linguistic components of contest-winning haiku and compare them to a control sample of poems published in an industry-standard journal. We look also at differences between haiku and senryu and what stylistic trends may have affected these poems over time. The results show that winning haiku are shorter than those in a representative journal. Journal poems also have fewer pronouns and more adjectives and nouns. All of the poems show a decrease in words over a decade-long time span. This trend may reflect changes in stylistic writing conventions. The length of such poems probably also relates to innate working memory span limitations. Haiku that limit the number of images and ideas within this limit likely facilitate cognitive processing and increase aesthetic appeal.