Input processing (IP) explores how language acquisition is influenced by comprehension, emphasizing the importance of form-meaning connections. It poses key questions about the conditions under which learners make these connections and outlines several principles focusing on the processing of content words, lexical meanings, and grammatical markers. IP is a critical aspect of a broader understanding of language acquisition, suggesting a need for models that encompass various elements of the learning process.

2.  Input processing (IP) is concerned with these
situations, the reason being that acquisition is,
to a certain degree, a by-product of
comprehension (see, e.g., Truscott & Sharwood
Smith, 2004).
 Although comprehension cannot guarantee
acquisition, acquisition cannot happen if
comprehension does not occur. Why? Because
a good deal of acquisition is dependent upon
learners making appropriate form–meaning
connections during the act of comprehension.

3.  IP is concerned with three fundamental
questions that involve the assumption that an
integral part of language acquisition is making
form–meaning connections during
comprehension:
1. Under what conditions do learners make initial
form–meaning connections?
2. Why, at a given moment in time, do they make
some and not other form– meaning
connections?
3. What internal psycholinguistic strategies do
learners use in comprehending sentences and
how might this affect acquisition?

4.  These claims are codified in the following IP principle :
1. The Primacy of Content Words Principle. Learners process
content words in the input before anything else.
2.The Lexical Preference Principle. Learners will process lexical
items for meaning before grammatical forms when both encode
the same semantic (“real world” information.
3. (Revised) Lexical Preference Principle. If grammatical forms
express a meaning that can also be encoded lexically (i.e., that
grammatical marker is redundant), then learners will not initially
process those grammatical forms until they have lexical forms to
which they can match them.

5. 4. The Preference for Non redundancy
Principle. Learners are more likely to process
non-redundant meaningful grammatical markers
before they process redundant meaningful
markers.
5. The Meaning before Nonmeaning Principle.
Learners are more likely to process meaningful
grammatical markers before non meaningful
grammatical markers.

6. 6. The First-Noun Principle. Learners tend to
process the first noun or pronoun they
encounter in a sentence as the subject.
7. The L1 Transfer Principle. Learners begin
acquisition with L1 parsing procedures
8. The Event Probability Principle. Learners
may rely on event probabilities, where
possible, instead of the First-Noun Principle
to interpret sentences.

7. 9.The Lexical Semantics Principle. Learners may
rely on lexical semantics, where possible, instead of
the First-Noun Principle (or an L1 parsing
procedure) to interpret sentences.
10.The Contextual Constraint Principle. Learners
may rely less on the First Noun Principle (or L1
transfer) if preceding context constrains the
possible inter- pretation of a clause or sentence.
11.The Sentence Location Principle. Learners tend
to process items in sentence initial position before
those in final position and those in medial position

8.  IP as a phenomenon should be viewed as
one part of a complex set of processes that
we call acquisition.
 Some kind of model of input processing will
need to coexist alongside models that deal
with how linguistic data are incorporated into
the developing system as well as how
learners access the system to make output,
and so on.