Computers (and many of their predecessors such as mechanical calculators and tabulating machines) were invented to assist humans in cognitive tasks such as calculation and data processing. Intelligence amplification takes place when computer interaction assists the human user in conceptual thinking by e.g. improving access to information. A lot of today's common computer applications (including the WWW) can be regarded as IA, even though the concept became unfashionable in the 1980s.
For permacomputing purposes, IA can be regarded as a subset of awareness amplification.
The use of punched cards and mechanical devices for "enhancing natural intelligence" was already suggested in 1832 by Semyon Korsakov and in the 1910s by Wilhem Ostwald. In these suggestions, each punch card would contain an idea or a "micro-thought", and a mechanical device would assist in finding and connecting them. Emanuel Goldberg (1930) and Vannevar Bush (1945) combined this concept with a microfiche viewer/searcher.
In Douglas Engelbart's Augmentation Research Center, these ideas evolved into a user interface prototype that supported a form of human-computer symbiosis. Hypertext and many modern GUI concepts originate from Engelbart's project.