Everett argues that theories and cultures create frameworks that dictate the limits of our perception. As an example, he recounts a time when he mistook a massive anaconda for a floating log. On a boat trip with his family, Everett saw a 40-foot “log” begin moving perpendicular to the current. As it approached, he realized that it was an enormous anaconda swimming toward the boat. He swerved and hit the snake with the motor’s propeller. The experience taught Everett that perception is learned through culture and experience; his culture taught him to look out for logs in the water, not giant snakes, creating a case of mistaken perception.

Early in his fieldwork, Everett suspected that Pirahãs simplified their speech for him because sentences always contained only one verb. He tested this by listening to Báigipóhoáí, a woman who talked loudly to other Pirahãs each morning. Her sentences were structured identically—still just one verb each. This puzzled Everett because he was actively searching for recursive structures like relative clauses, which linguists believed existed in all languages.

When Everett asked Kóhoi whether two simple sentences sounded acceptable, hoping for a correction with a relative clause, Kóhoi simply repeated them, confirming their correctness. One day, Everett overheard Kóhoi tell his son Paitá to bring back some nails; he then added that Dan had bought those very nails and that they were the same. This conveyed the meaning of an English relative clause through three separate sentences rather than embedding one inside another.

Everett describes recursion—the embedding of one phrase inside another of the same type—and addresses its importance to linguistics. In 2002, Hauser, Chomsky, and Fitch labeled recursion the unique component of human language, claiming that it enables infinite sentence production. Everett challenges this by arguing both that Pirahã lacks recursion and that recursion isn’t actually “all that important” (228). As a consequence, some Chomsky proponents have redefined recursion as simple compositionality, but Everett criticizes this for conflating language with general reasoning, contradicting Chomsky’s own distinction between sentence and story structure.

Recursion can be tested by looking for phrases within phrases, often marked by complementizers like “that” or by intonation, neither of which are found in Pirahã. Everett cautions against conflating language and reasoning, citing Herbert Simon’s 1962 article showing that recursion exists in human reasoning outside language. Simon used the parable of two watchmakers—Hora, who used recursive sub-assemblies, and Tempus, who did not—to illustrate recursive efficiency.

A key prediction of recursion is that no longest sentence exists; a phrase can be extended indefinitely. However, Everett provides a complete Pirahã sentence that becomes ungrammatical if further lengthened. He also addresses the claim that iteration equals recursion, noting that this would make his dog’s repeated barking recursive, thus not uniquely human.

Everett goes on to connect the lack of recursion to the immediacy of experience principle: Embedded clauses contain non-asserted background information, violating the principle’s requirement that declarative utterances contain only assertions. Pirahã also prohibits more than one possessor in a noun phrase. He proposes that Pirahã may lack complex syntactic structures altogether, with sentences functioning like beads on a string to prevent non-assertions from appearing within assertions.

The lack of recursion also correctly predicts that Pirahã lacks coordination (“and”) and disjunction (“or”). To express “either/or,” Pirahãs instead use separate sentences conveying uncertainty.

This research led Everett to abandon the idea of a specialized “language organ” and his belief in universal grammar. He concluded that language arises from general human reasoning rather than a genetic endowment specific to grammar. While Pirahã grammar may be finite, the language itself is not because stories contain recursive structures like subplots. This challenges Chomsky’s theory by demonstrating that a non-finite language can have a finite grammar. He compares this to chess—finite but highly productive. Following Simon, he argues that recursion is a general cognitive ability that creates emergent hierarchical structures in language when culturally efficient. He proposes that similar non-recursive languages may exist in other isolated cultures with esoteric communication and concludes that linguistics should be part of anthropology, with languages studied within their cultural context.

Everett recounts helping a Brazilian graduate student who wanted to study the Pirahã. He recorded an introductory message in Pirahã on the student’s tape recorder. The Pirahãs, familiar with two-way radios, assumed that the device worked the same way. The student later met Everett in São Paulo, excitedly claiming to have recorded a Pirahã creation myth—which Everett had said did not exist. On the tape, the student asked creation questions in Portuguese. A Pirahã man merely repeated the last words of each question. Background prompts led him to say words like “bananas” and “papaya.” Then, the man at the microphone switched to fluent Pirahã, addressing Everett through the recorder to request matches, cloth, and medicine. The student had mistaken this direct address for a creation myth.

Everett frames this misunderstanding as the universal problem of communicating across different cultural conventions—the student spoke “crooked head” (Portuguese) to “straight heads” (Pirahãs). Everett explains that Pirahã epistemology requires eyewitness testimony, though lying is common. This resembles pragmatism, as developed by William James and C. S. Peirce: Knowledge is tested by usefulness, not abstract truth. Culture prepares us well for local environments but can be an impediment elsewhere.

One night, while walking a jungle path with a teenager named Kaioá, Everett used a flashlight while Kaioá walked behind him in darkness. Kaioá quietly pointed out a caiman ahead. Everett saw nothing with his flashlight, so Kaioá told him to turn it off. Everett still saw nothing until Kaioá pointed out two bloodlike eyes. Kaioá ran ahead and beat the three-foot caiman unconscious with a stick. Everett reflects that his urban culture, which prepared him to look for cars and pedestrians, didn’t prepare him to perceive dangers like caimans on a jungle path.

In another example, Everett recounts swimming with Kóhoibiíháí while women on the riverbank gutted a singed monkey and washed its entrails into the water nearby. The water began to froth. Everett’s companion told him that piranhas were attracted to the blood and guts. Everett became concerned, but Kóhoibiíháí calmly assured him that the piranhas were only interested in the monkey guts. Everett reflects that his culture gave him an inaccurate, fear-based understanding of piranhas but didn’t prepare him to recognize their signs in the wild or remain calm around them.

Conversely, Pirahã culture doesn’t prepare the Pirahãs for urban life; for example, an MIT/Stanford study confirmed that Pirahãs have difficulty with transformed photos, providing evidence for difficulty with visual abstraction.

In 1979, while his wife, Keren, recovered from malaria, Everett brought Xipoógi and Xahoábisi to Pôrto Velho to continue language work. The men, self-conscious in their single pairs of gym shorts, asked to buy Western clothes. They had many questions about cars, buildings, and pavement. After shopping, they insisted on walking single-file on wide sidewalks—a habit from narrow jungle paths. As Everett led them across a busy street, he turned three-quarters across to find them frozen in fear and had to lead the panicking men back to safety. Xipoógi declared that cars were worse than jaguars.

Everett connects these cultural differences to the scientific debate over Pirahã and Chomsky’s theory of universal grammar—a language-specific component of human biology. He argues that Chomsky’s influence created a deductive, theory-first culture in linguistics that devalues fieldwork. He contrasts inductive (data-first) and deductive (theory-first) approaches, listing Chomskyan cultural values: Fieldwork is unnecessary, studying one’s native language is as important as studying previously undocumented languages, and grammar is independent of culture.

Invoking Thomas Kuhn’s concept of scientific revolutions, Everett presents Pirahã as a source of “recalcitrant facts” requiring a new theoretical approach. He critiques Steven Pinker’s The Language Instinct for minimizing culture’s role in shaping grammar. While culture determines vocabulary—Scottish haggis, Brazilian jeito, Pirahã kaoáibógi—Everett’s main point is that culture shapes grammar itself.

Everett acknowledges similarities among languages that Chomsky attributes to genetics: similar parts of speech, processing constraints (like difficulty with center embedding), and semantic constraints (verbs require no more than three nouns). He contrasts Chomsky’s theory with B. F. Skinner’s rejected behaviorism but argues that Chomsky’s theory is now failing: New research has emerged, the theory has become vague and untestable, and languages are more different than the theory allows.

Pirahãs’ conversational topics are limited by culture, much like academics who mostly discuss their own fields. Knowledge is not as “portable” as we think, and localized language is often not particularly useful in other environments. Everett argues that the same is true of language theories; what sounds good in a classroom might not work in the field. 

Everett concludes that grammar is less important than culture-based meanings and constraints and that linguistics belongs more to anthropology than psychology. Languages must be studied within their cultural context. He ends by foreshadowing that his Pirahã experiences would lead to a profound change in his own spirituality.