- Esperanto is faster to learn than other European languages (3 studies), and
- On average Esperanto helps students learn European and Asian languages faster than studying those languages alone (4 studies)
Alan J. Bishop, "Ekparoli Project Report" 1994 - 1997
angelfire.com/ok/andreo/ekparoli.report.html
web.archive.org/web/20040301110024/http://www.education.monash.edu.au/projects/esperanto/Ekrep97.htm
- 2 years of Esperanto, followed by a year of Japanese, Indonesian, French or German, leads to above-average knowledge of the final language
Alvino E. Fantini, and Timothy G. Reagan, "Esperanto and Education: Toward a Research Agenda"
Sponsored by the Esperantic Studies Foundation 31 October 1992
http://web.archive.org/web/20010310011424/http://www.esperantic.org/esf/f-r2.htm#two
Fantini+Reagan report on several studies:
(A) Division of Psychology, Institute of Educational Research, Teachers College, Columbia University. 1933. "Language Learning: Summary of a Report to the International Auxiliary Language Association in the United States." New York: Bureau of Publications, Teachers College, Columbia University.
- "On the whole, with expenditures of from ten to a hundred hours, the achievement in the synthetic language will probably be from five to fifteen times that in a natural language, according to the difficulty of the latter." (p.7)
- "at the end of two years ... the French scores show 9.7 points more progress for the Esperanto group, which had studied French during one of the two years, than was made by the non-Esperanto group, which had studied French during the two years" (p.30)
(B) Halloran, J. H. 1952. A four year experiment in Esperanto as an introduction to French. The British Journal of Educational Psychology 22: 200-204.
Williams, Norman. 1965. A language teaching experiment. Canadian Modern Language Review 22, 1: 26-28.
Fantini+Reagan say, "Halloran did find that more academically gifted students tested slightly better in French if they had four years of French instruction rather than a year of Esperanto followed by three years of French. Williams (1965) argued, however, that Halloran's approach was actually biased against the Esperanto group, and that no students were disadvantaged by taking Esperanto first. Halloran and Williams both found that less academically able students benefitted from initial Esperanto instruction. Although a number of methodological problems and limitations in the studies of Halloran and Williams can be raised, it would appear that their results are for the most part reasonable representations of the Denton experience, and would tend to support the claims for the propaedeutic effects of Esperanto study, as well as those concerned with the positive effects of Esperanto study for special needs students."
(C) Sonnabend, Helmut. 1979. Esperanto: Lerneja Eksperimento. Pisa: Edistudio.
Fantini+Reagan quote Maxwell:
- German "Children learning Esperanto were able to learn more in two years than other [German] children learning English in three or four years . . . the Esperanto groups would require a total of 2.5 years to obtain 100% mastery of the material presented in this test, whereas the English groups would require 5.3 years to achieve a corresponding result." (p.58, Maxwell, Dan. 1988. "On the acquisition of Esperanto." Studies in Second Language Acquisition 10, 1:51-61)
(D) A 1978-87 series of studies in Polish:
- Frank, Helmar. 1987a. Propedeutika valoro de la internacia lingvo: Kibernetika teorio kaj empiriaj rezultoj de la lingvo-orientiga instruado de la Internacia Lingvo kiel bazo de pli posta lernado de etnaj lingvoj. In Serta Gratvlatoria in Honorem Juan Régulo, II (Esperantismo) (La Laguna: University de La Laguna), pp. 213-222.
- Frank, Helmar. 1987b. Wartosc propedeutyczna jezyka miedzynarodowego. Miedzynarodowa Komunikacja Jezykowa/Internacia Lingva Komunikado: Materialy Konferencyjne -- IV. Lódz: Uniwersytet Lódzki, Zrzeszenie Studentow Polskich, Studenckie Kolo Naukowe Esperantystów, pp. 124-136.
- Frank, Helmar. 1978. Grundlagen und sprachpädagogische Anwendung einer informationstheoretischen Transferanalyse. Grundlogenstudien aus Kybernetik und Geisteswissenschaft 19: 75-88.
- Frank, Helmar. 1976. Mallonga enkonduko en la kibernetikan pedagogion/Kurze Einfuehrung in die Kybernetische Pädagogik. In H. Behrmann and S. Stimec, eds., Bildung und Berechnung/Klerigo kaj Prikalkulado (Alsbach: Leuchtturn-Verlag), pp. 9-55.
- Frank, Helmar, and Barandovska, Vera. 1991. Lernpliffaciligo pro antaumetitaj lingvokursoj. Internacia Pedagogia Revuo 21, 4: 11-15.
- Geisler, Evelyn. 1979. La unuaj mezuradoj pri la lernfaciligo internacia kaj angla lingvoj. Europa Dokumentaro 21: 9-10. Meder, Brigitte. 1978. Efikoj de la lingvo-orientiga instruado al la lernsukceso en la mezgrada lernejo. Europa Dokumentaro 20: 15-18.
- Meinhardt, Gard. 1978. Latent knowledge of vocabulary of the international language, arising from one's native language. Europa Dokumentaro 18: 13-15.
- "The results obtained by the researchers at the Instituto pri Kibernetika Pedagogio are of quite high quality, and generally appear to support both claims about the ease of learnability of Esperanto and claims about its propaedeutic benefits."
Other reports which I have not been able to find:
1958-63 Finnish students learning German faster by learning Esperanto first, than by just learning German . This would be significant, since Finnish is unrelated to both German and Esperanto.
- J. VILKKI (?), Vilko Setala, "La eksperimenta instruado de Esperanto en la Geknaba Mezgrada Lernejo de Somero" (Suomio). El Popola Åinio, 1963, n. 1, pp. 38-39.
- Vilko Setala, Vizito al la eksperimenta lernejo en Somero, Finnlando. Esperanto, June, 1961, 107 p.
1962-63 Hungarian students learned Esperanto more easily than Russian, German, or English.
- Istvàn Szerdahelyi, La didaktika loko de la Internacia Lingvo en la sistemo de lernejaj studobjektoj. In Esperanto: La internacia lingvo: sciencaj aspektoj, (editor: Detlev Blanke), Kulturbund der DDR, Berlin, 1979, p. 211-219.
- Günter Lobin, "Die Internacia Lingvo als Bildungskybernetisches Sprachmodell," p. 59.
A few other studies are listed in Wikipedia, without findings or citations. The list appears to be translated from an Italian original, or a French translation.