In chapter 12, Rocky and Ryland work to expand their shared vocabulary, arriving at translations between Eridian and English. When Ryland’s software encounters a new Eridian word, he inputs that word in his database. Rocky, however, does not appear to take any notes during this process, simply paying attention and remembering everything he is told. This leads to Ryland determining that Rocky possesses what might be called a “photographic memory” 12.083.

Photographic memory is a popular psychology topic, often used casually to describe people who simply have a good memory. However, true photographic memory, the ability to recall a scene or page of text “at will and examine it in detail”, has never been verifiably demonstrated. Eidetic memory is a term often used interchangeably with photographic memory, although there is some evidence for the former, which can include senses other than vision.

Ryland acknowledges in 12.084 that “It’s probably even more complicated than that” and “Maybe Eridians are just really good at remembering sounds.” Given that the existence of photographic/eidetic memory remains a somewhat controversial topic, the path to verifying Ryland’s initial claim is clear: We simply need to study more Eridians!