Memory and Text Comprehension 579the schematic structure of the story itself. In other words, the
reader is an expert. In reading such a text, LTWM comes into
play in two ways.
First of all, the reader activates relevant knowledge auto-
matically. The necessary concepts, frames, scripts, schemata
(Schank & Abelson, 1977), and personal experiences imme-
diately link information in the text held in working memory
to the reader’s general knowledge and episodic memory. That
does not mean that this knowledge enters into short-term
working memory, or becomes conscious; it only means that it
is available to be used, should there be any reason to use it.
Text comprehension researchers have described this process
as one of making inferences(W. Kintsch, 1993). This is not
always an accurate description, if we mean by making an
inferencethat some statement not directly contained in the
text is derived from the text with the help of relevant
background knowledge and becomes part of the mental
representation of the text. That happens, or can happen, but
knowledge activation does not necessarily imply an explicit
inference. Activated knowledge simply becomes available
for further use—if there is further use. There is a definite
need for knowledge activation in many experiments, when
the experimenter asks a question or presents a relevant word
in a lexical decision task. In uncontrived situations the need
for knowledge activation may arise spontaneously, as when a
reader detects a gap in his or her understanding that can only
be filled through some problem-solving activity involving
that knowledge. But in the normal course of automatic read-
ing comprehension, activated knowledge merely stands by in
LTWM. For example, consider the bridging inference in-
volved in the well-known sentence pair of Haviland and
Clark (1974):
We checked the picnic supplies. The beer was warm.Understanding this sentence does not involve the inference
Picnic supplies normally include beer,in the sense that this in-
ference statement becomes an explicit part of the mental rep-
resentation of this text. Rather,picnic suppliesas well asbeer
both make strongly associated information, such asbeer is
frequently a part of picnic supplies,available in LTWM. This
requires a little extra processing time; 219 ms in this
experiment, in comparison with a control sentence pair in
whichbeerwas explicitly mentioned in the first sentence.
This knowledge activation suffices to establish the coherence
between the two sentences and allows the comprehension
process to proceed without the reader ever becoming
conscious of a bridging problem. Note that this use of LTWM
entirely depends on the availability of strong automatic
retrieval links between the words of the sentence and the
contents of long-term memory. Consider a different example:The weather was calm. Connors used Kevlar sails.Anyone but an expert sailor will not automatically find this to
be coherent text, because there is nothing in our long-term
memory that strongly linkscalm weathereither toConnorsor
toKevlar sails. We might figure out that perhaps Kevlar sails
are good for calm weather—but that is not an automatic
processes. Rather, it is a controlled problem-solving process
with significant time and resource demands. Long-term work-
ing memory functions only in those situations in which we
can rely on strongly overlearned knowledge: that is, in do-
mains where we are experts.
A second way in which LTWM plays a role in text com-
prehension is by ensuring that the mental representation of
the text that already has been constructed remains readily ac-
cessible as reading continues. If we read something, it is not
only necessary to link what we read with our long-term store
of knowledge and experiences, but it is also necessary that
we link what we read now with relevant earlier portions of the
text. These portions cannot be held in short-term working
memory. We know from our own experience as well as from
experimental studies (e.g. Jarvella, 1971) that no more than
the current sentence—if it is not too long—is held in the focus
of attention during reading. We also know that we effortlessly
retrieve referents and relevant propositions from earlier por-
tions of the text when needed to construct the meaning of the
current sentence. Comprehending a text implies linking its
various parts effectively in such a way as to permit easy re-
trieval. That is to say, comprehension implies the construction
of a new network in LTWM. Of course, unlike the well-
established links between text and long-term knowledge, the
newly generated textbase is subject to forgetting.
Thus, LTWM during text comprehension includes short-
term working memory—the sentence currently in the focus
of attention—plus relevant knowledge activated from long-
term memory that is directly linked via strong retrieval struc-
tures to the current contents of short-term working memory.
It also includes the textbase (including contextual informa-
tion, such as reading goals) that has already been generated,
of which the presently worked-on sentence is a continuation.
Long-term working memory as previously described is inci-
dental, an inherent by-product of the process of text compre-
hension. This is also the case for the physician and chess master.
The chess master learns to play chess—not to memorize chess
boards. It is worth noting, however, that LTWM can be inten-
tional—as in the case of the runner who invented an encoding
and retrieval system that allowed him to memorize long se-
quences of random digits (Ericsson, Chase, & Faloon, 1980), or