Standard
 generative
 grammars
 describe
 language
 in
 terms
 that
 appear
 distant
 from
 considerations
 of
 everyday,
 real‐time
 language
 processes.
 To
 some
 this
 is
 a
 critical
 flaw,
 while
 to
 others 
this 
is 
a 
clear 
virtue.
 One
 type 
of 
generative 
grammar 
defines 
a 
well‐formed
 sentence
 as 
a 
static, 
structured
 representation 
that 
simultaneously
 satisfies 
all 
relevant 
constraints 
of 
the
 language,
 with 
no 
regard 
to 
how
 the 
representation 
is 
assembled 
(e.g., 
Sag,
 Wasow, 
& 
Bender,
 2003).
 Another
 type
 of
 generative
 grammar
 defines
 a
 well‐formed
 sentence
 as
 a
 derivation,
 or
 sequence
 of
 representations,
 that
 describes
 how
 the
 sentence
 is
 gradually
 assembled,
 often
 including 
various 
transformations
 that
 move
 words
 or 
phrases 
from
 one 
position
 to 
another 
in 
a
 structure.
 In
 the
 most
 popular
 current
 version
 of
 the
 derivational
 approach,
 derivations
 proceed
 ‘upwards’,
 starting
 from
 the
 most
 deeply
 embedded
 terminal
 elements
 in
 the
 sentence,
 which
 are
 often
 towards
 the
 right
 of
 a
 sentence
 (e.g.,
 Chomsky,
 1995;
 Carnie,
 2006).
 Such
 derivations
 tend
 to
 proceed
 in
 a
 right‐to‐left
 order,
 which
 is
 probably
 the
 opposite
 of
 the
 order 
in 
which 
sentences 
are 
assembled
 in 
everyday 
tasks 
such
 as 
speaking 
and
 understanding.
 Since
 these
 theories
 make
 no
 claim
 to
 being
 accounts
 of
 such
 everyday
 processes,
 the
 discrepancy
 causes
 little
 concern
 among
 the
 theories'
 creators.
 Generative
 grammars
 are
 typically
 framed
 as
 theories
 of
 speakers’
 task‐independent
 knowledge
 of
 their
 language,
 and
 these
 are
 understood
 to
 be
 distinct
 from
 theories
 of
 how
 specific
 communicative
 tasks
 might
 put
 that 
knowledge
 to 
use.


Set
 against
 this
 background
 are
 a
 number
 of
 recent
 proposals
 that
 various
 linguistic
 phenomena
 can
 be
 better
 understood
 in
 terms
 of
 derivations
 that
 incrementally
 assemble
 structures
 in
 a
 (roughly)
 left‐to‐right
 order.
 One
 can
 evaluate
 these
 proposals
 based
 simply
 on
 how
 well
 they
 capture
 the
 acceptability
 judgments
 that
 they
 aim
 to
 explain,
 i.e.,
 standard
 conditions
 of
 'descriptive
 adequacy'.
 But
 it
 is
 hard
 to
 avoid
 the
 question
 of
 whether
 it
 is
 mere
 coincidence
 that
 left‐to‐right
 derivations
 track
 the
 order
 in
 which
 sentences
 are
 spoken
 and
 understood.
 It
 is
 also
 natural
 to
 ask
 how
 left‐to‐right
 derivations
 impact
 the
 psychological
 commitments
 of
 grammatical
 theories.
 Are
 they
 procedural
 descriptions
 of
 how
 speakers
 put
 together 
sentences 
in 
real 
time 
(either 
in 
comprehension 
or 
in 
production)? 
 Do 
they 
amount 
to
 a
 retreat
 from
 linguists’
 traditional
 agnosticism
 about
 ‘performance
 mechanisms’?
 These
 are
 questions
 about 
what 
a 
grammatical 
theory 
is 
a 
theory 
of, 
and
 they 
are 
the 
proverbial 
elephant
 in
 the
 room
 in
 discussions
 of
 left‐to‐right
 derivations
 in
 syntax,
 although
 the
 issues
 have
 not
 been
 explored 
in 
much 
detail. 
Here 
we 
summarize 
the
 current 
state 
of 
some
 of
 the 
evidence 
for
 left‐to‐right
derivations 
in 
syntax, 
and 
how 
this 
relates 
to 
a 
number 
of 
findings 
by 
our 
group 
and
 others
 on 
the 
nature 
of 
real‐time
 structure 
building 
mechanisms. 
Some
 of 
these 
questions 
have
 been
 aired
 in
 previous
 work
 (e.g.,
 Phillips
 1996,
 2004),
 but
 we
 have
 come
 to
 believe
 that
 the
 slogan
 from
 that
 earlier
 work
 (“the
 parser
 is
 the
 grammar”)
 is
 misleading
 in
 a
 number
 of
 respects, 
and
 we 
offer 
an 
updated
 position 
here.