On the podcast in which she reads Brooks’s poem “To Be in Love,” Ada Limón mentions the work of science writer Florence Williams, who explored the physiological effects of love and heartbreak in her book Heartbreak: A Personal and Scientific Journey. While Brooks doesn’t narratively recount the intimacy of the partners in “To Be in Love,” through the speaker’s indications of emotion we can—as Limón points out—see their physical response to the absence of the lover by applying Williams’s theories.

In a February 2022 interview with National Public Radio, Williams explains that when a couple first falls in love, their bodies “co-regulate” (See: Further Reading & Resources). She says that “a lot of studies [show] that when you put a couple in a brain scanner and you give them a task, their brain waves actually sync up.” This co-regulation is expressed in Brooks’s poem when the speaker says that to be in love is “To look at the world / Through his eyes” (Lines 4-5), and that the couple “are tasting together / The winter, or a light spring weather” (Lines 10-11). The couple’s thoughts and experiences are synchronized.

However, Williams also notes that “when our partner leaves or sort of disappears,” we’re affected by stress hormones.