Reflexes are divided by Pavlov1 into two main groups, conditioned and unconditioned. The unconditioned, so designated because of their independence of, or slight dependence on, surrounding conditions, are those reflexes which are transmitted by heredity and which are characteristic of the species rather than of the individual animal itself. They appear in every member of the species provided the central nervous system is normal. They may disappear with age or appear only in maturity, but they are certain to reappear in the next generation and follow a similar course.
Reflexes which are present during the first few months and which may be traced back to developmental attributes are the Moro embrace reflex, the fear reflex, the sleeping attitude and the hand reflex. The embrace reflex was first described by Moro in 1918.2 He found that on placing an infant on a table and then forcibly striking the table
GORDON MB. THE MORO EMBRACE REFLEX IN INFANCYITS INCIDENCE AND SIGNIFICANCE. Am J Dis Child. 1929;38(1):26-34. doi:10.1001/archpedi.1929.01930070038004