The ultimate goal of reading is to extract meaning from printed words. However, the
mechanisms that mediate orthography and semantics are not well-understood, and have
rarely been implemented in computational models. To address this puzzle, one of the
strategies cognitive scientists have begun to use is to examine semantic richness
effects. Semantic richness effects refer to the finding that words associated with
relatively more semantic information are recognized faster and more accurately, due
to their possessing richer, better-specified semantic representations. Importantly,
semantic richness is not a unitary concept. Instead, it draws on various theoretical
perspectives and can vary along multiple dimensions. Thus, by examining which dimensions
of semantic richness influence visual word recognition behavior, we gain insight about
which theoretical perspectives seem to be promising descriptions of the process by
which meaning is extracted from print. Our goal for this Frontiers Research Topic
was to highlight the latest findings regarding semantic richness and theoretical developments
on the issue of semantic processing. Our hope was to provide a forum for state-of-the-art
research in this field, and to foster new theoretical advances. The 17 contributions
that comprise the Research Topic certainly represent the state of the art; methodologies
include ERP, fMRI, TMS, and behavioral approaches, and involve both intact and patient
populations. Together, these contributions give rise to a number of inferences about
semantic richness effects and implications of those effects for our understanding
of semantic processing effects in visual word recognition.
Meaning is multidimensional
The Research Topic contributions build on previous literature, providing further empirical
support for several semantic richness dimensions and the frameworks from which those
dimensions are derived. Gould et al. (2012); Recchia and Jones (2012); Yap et al.
(2012) report semantic neighborhood effects (faster responses for words with more
semantic neighbors or denser semantic neighborhoods) in naming and lexical decision
tasks, providing evidence that lexical co-occurrence is an important dimension in
semantic memory. Hargreaves and Pexman (2012); Taler et al. (2013) show that lexical
decision performance is facilitated for words with more meaning senses, providing
support for the notion that meaning information is represented in a distributed fashion.
The typicality effects reported by Woollams (2012) support the claim that words' feature
structure is important to semantic memory. Further, Recchia and Jones (2012); Yap
et al. (2012) show that words that generate more features in feature listing tasks
produce faster naming, lexical decision, and semantic categorization responses, Hargreaves
et al. (2012a) report that those words are also better remembered in free recall.
Finally, there is evidence supporting embodied frameworks of semantic memory from
studies reported by Esopenko et al. (2012); McNorgan (2012). Further support for the
embodied framework is provided by Hansen et al. (2012); Hargreaves et al. (2012b);
Newcombe et al. (2012); Tousignant and Pexman (2012); Yap et al. (2012), as all of
these studies report body-object interaction effects (faster processing for words
that refer to objects the human body can easily interact with) in tasks that include
naming, lexical decision, and semantic categorization. Convergent evidence that perceptual
and sensorimotor information are important dimensions of meaning comes from the observations
of Hargreaves and Pexman (2012); Newcombe et al. (2012); Yap et al. (2012) by which
imageability effects (faster responses for words that are associated with imagery)
are reported in a number of word recognition tasks.
In addition, in the contributions of Hargreaves and Pexman (2012); Newcombe et al.
(2012); Recchia and Jones (2012); Yap et al. (2012) there are demonstrations that
multiple semantic richness effects can be observed simultaneously, suggesting that
each richness dimension explains unique variance in word recognition behavior. The
implication is that no single dimension (and associated framework) will be sufficient
to explain the process by which meaning is derived from print. Instead, as argued
by Dilkina and Lambon Ralph (2013); Jones and Golonka (2012); Kalénine et al. (2012),
semantic memory is multidimensional.
Semantic processing is variable and dynamic
The findings of Kalénine et al. (2012); Woollams (2012) support the inference that
semantic processing is variable as a function of disease. By studying the dimensions
of meaning that are more resistant to brain damage these studies provide important
new clues about the structure of meaning in the mind. The contributions of Hargreaves
and Pexman (2012); Hansen et al. (2012) show that semantic processing is variable
as a function of both short-term and long-term experience. Further variability is
revealed in Jones and Golonka (2012); Kalénine et al. (2012); Rabovsky et al. (2012);
Taler et al. (2013), where the timecourse of processing is examined in order to dissociate
richness dimensions. Results show, first, that semantic information is generated quite
early in the process of word recognition and, second, that different dimensions of
meaning may be influential at different times as semantic processing unfolds.
Contributions by Gould et al. (2012); Hansen et al. (2012); Hargreaves and Pexman
(2012); Recchia and Jones (2012); Tousignant and Pexman (2012); Yap et al. (2012)
demonstrate that the process of generating meaning from print is a dynamic one, where
contextual factors like task demands shape the information that is generated from
letter strings. These demonstrations are consistent with the notion of a flexible
lexical processor (Balota and Yap, 2006) that is sensitive to task contexts so as
to optimize task performance via attentional control. The present findings also permit
the inference that the semantic richness effects observed in a given task do not provide
veridical insight about static semantic representations. Semantic representation is
not fixed and so cannot be revealed in a single task or context (Kiefer and Pulvermüller,
2012). Rather, meaning is actively constructed and shaped to meet task demands. Dimensions
that are important in one context may not be important in others. Certainly, it now
seems clear that there are many candidate dimensions of meaning, but the context will
dictate the actual effects observed.
Future directions: abstract meaning and other challenges
As has been typical in the lexical semantic literature, most of the contributions
in this Research Topic focus on semantic processing of concrete words, like TRUCK,
where the word refers to an object or entity in the world. As such, while we know
quite a lot about how concrete meanings might be processed, we know much less about
how abstract meanings are understood. This is problematic because abstract words make
up a large part of the average person's vocabulary; the focus on concrete word meaning
creates a situation where we are studying only part of the human lexicon. In two of
the present papers, however, the authors use semantic richness effects to begin to
study semantic processing of abstract words, like TRUTH. Newcombe et al. (2012); Recchia
and Jones (2012) explore semantic richness dimensions that could be relevant to abstract
word meaning. Since many of the richness dimensions that are influential for concrete
words are not as relevant to the meanings of abstract words (e.g., those dimensions
that refer to objects), the richness dimensions that influence abstract word meaning
are somewhat different. For instance, Newcombe et al. (2012) show that while body-object
interaction is an important dimension for concrete words, emotion information is important
for abstract words, consistent with predictions derived from the embodied cognition
framework of Kousta et al. (2010). In addition, Recchia and Jones (2012) show that
richer linguistic contexts (larger semantic neighborhoods) facilitate abstract word
processing. These contributions are first steps in the study of abstract word meaning,
and this issue will need to be taken up in future research.
We suggest, further, that future research on this topic should continue to explore
several of the other important avenues opened here, for instance, the role of individual
differences in semantic processing and the joint effects of different semantic richness
dimensions. There are additional issues that have not yet received much attention
but will be important; for instance, the issue of whether semantic richness dimensions
influence processing in a linear or non-linear manner, and the extent to which richness
effects extend beyond single-word contexts to influence processing of phrases and
sentences. These and other research questions should be addressed in order that we
are able to further refine our understanding of how word meaning is processed in mind
and brain.
Conclusion
The contributions in this Frontiers Research Topic highlight a number of dimensions
of semantic richness and the contexts in which they are observed. The contributions
cohere around several insights: multiple types of information are constitutive of
word meaning, and semantic processing is a dynamic process that must be tracked with
careful consideration of context and other sources of variability; the challenges
for theories of semantic meaning are to capture this multidimensionality, and to extend
their reach to include abstract meanings.