Chapter 1 the study of collocations

2.1  Morphology 
 
 
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The Natural Order Hypothesis in Krashen's Monitor Theory suggests 
that there is a natural order of acquisition of L2 rules.  Some of them are early-
acquired and some are late-acquired.  This order does not necessarily depend 
on simplicity of form.  It can also be influenced by classroom instruction 
(Krashen 1985).  Evidence for the Natural Order Hypothesis was provided by a 
series of research studies investigating morpheme acquisition orders and 
showing that grammatical morphemes elicited in free speech and with the use 
of specifically designed instruments (e.g. the Bilingual Syntax Measure) 
constitute a natural order of morpheme acquisition for performers (Houck, 
Robertson & Krashen 1978; Krashen, Houck, Giunchi, Bode, Birnbaum & Strei 
1977).  Krashen's Natural Order for the acquisition of 9 English morphemes, 
from the early acquired morphemes (top) to the late acquired ones (bottom), are 
given below in Table 6: