The Deep Dream
The dream & delayed birth: an economical way to grow a human during long space voyages so that they can be old enough to work (or be studied, in this case) when the voyage is over. This means they grow up in a false reality, and may only take their first true breaths when they’re technically a few years old.
As the Siren settlement project was operated by a for-profit corporation, they aimed to cut corners wherever necessary. As such, they purchased the licence to use pre-made, generic Deep Dreams designed for normal children. Their use on Ishmael and the beta-generation Sirenians had ultimately catastrophic consequences, including the death of one and the permanent incapacitation of another, as well as issues with de-realisation and dysmorphia across the board.
The dream was designed to provide a growing child with all the basic information they 'ought' to have known by their tenth year of age. This included language, mathematics, and simulated team sports during which the physical body would move, to develop muscle tone. The producers of these dreams advertised that a child would be born 'socialised' - they would not respond like feral animals to situations such as medical check-ups or injury. In reality it was well known that children raised in this sort of dream had worse outcomes than children with normal childhoods, or children who had simply been cryogenically frozen for extended space travel. It is important to note that the children of the settlers who made the journey to Siren were not subjected to the dream, but frozen instead, like their parents.
The ending of the dream was designed to ease a child into birth. They would dream that they were falling asleep in their bed, tucked in by their parent figure, about to travel to some new location in the morning. These memories were not supposed to persist after birth, though this was not always the case, and several of the alpha and beta generation Sirenians did recall their parent figure in the dream, to whom they had become deeply attached. Of course, these parents did not truly exist.