Meaning structures and mental representations

This paper argues for a distinction between meaning structure and mental representation, and presents the outlines of a theoretical model of their interrelationship. Meaning structures are defined as structures in the human mind/brain which develop as the combined result of genetic predispositions and individual experience, and lead to relatively stable patterns of perceiving, thinking, feeling, behaving, etc. Mental representation is defined as the aspect of mental processes which involves imagining and thinking of things that are not perceptually present. It is suggested that the mind includes a central network of meaning structures (CNMS) for the storage of information, and a number of other subsystems (e.g., perceptual systems, behavioral systems, and a verbal system) for the processing of externally and internally generated information. Against the dual-coding theory, it is argued that there is one code for the long-term storage of information, but several codes for the processing of information. Mental representations are seen as products of activation that is spread from the CNMS to more peripheral systems. The spread of activation from the CNMS to perceptual systems results in mental imagery; when activation spreads to the verbal system the result is conceptual thinking; and when activation spreads to behavioral systems it produces intentions. It is argued that this conceptual model can help to solve some basic theoretical problems that have plagued cognitive psychology.     

Parts and boundaries.

Within the framework of Conceptual Semantics, a family of conceptual features and functions is developed that accounts for phenomena in the semantics of noun phrases such as the mass-count distinction, plurality, the partitive construction (a leg of the table), the constitutive construction (a house of wood), the "Universal Packager" (three coffees), and boundary words such as end, edge, and crust. Using the strong formal parallelism between noun phrase semantics and event structure that is a hallmark of the Conceptual Semantics approach, the features and functions of the NP system are applied to a wide range of problems in event structure, for example the analysis of the Vendler classes, the meaning of the progressive, the "imperfective paradox", and "aktionsarten" such as the syntactically unexpressed sense of repetition in The light flashed until dawn. Crucial to the analysis is that these features and functions can be expressed in syntactic structure either by being part of lexical conceptual structure, or by use of a morphological affix, or by being associated with the meaning of a construction such as N of NP or nominal compounding. Alternatively, they may remain unexpressed altogether, being introduced into the conceptual structure of a phrase by "rules of construal". This shows that lexical semantics and phrasal semantics interpenetrate deeply, and that there is no strict one-to-one correspondence between syntactic and semantic structures. In addition, the analysis provides further evidence that natural language semantics must be based on a psychological view of meaning--it must be concerned with how language users are constructed to understand and schematize the world.     

Horwich on meaning and use

Paul Horwich claims that theories of meaning ought to accommodate the commonsense intuition that meanings play a part in explaining the use of words. Further, he argues that the view that best does so is that according to which the meaning of a word is constituted by a disposition to accept, in some circumstances, sentences in which it features. I argue that if meanings are construed thus, they will in fact fail to explain the use of words. I also argue that if we insist, as Horwich does, on the commonsense assumption that meanings are a species of entity, all versions of the view that meaning is constituted by our dispositions to use words will have to be rejected. I do not, however, claim that such theories ought to be rejected. My point is that they are incompatible with the requirements of commonsense. Further, I suggest that it is premature to impose such requirements on theories of meaning.     

Syntactic structure and artificial grammar learning: the learnability of embedded hierarchical structures

Embedded hierarchical structures, such as "the rat the cat ate was brown", constitute a core generative property of a natural language theory. Several recent studies have reported learning of hierarchical embeddings in artificial grammar learning (AGL) tasks, and described the functional specificity of Broca's area for processing such structures. In two experiments, we investigated whether alternative strategies can explain the learning success in these studies. We trained participants on hierarchical sequences, and found no evidence for the learning of hierarchical embeddings in test situations identical to those from other studies in the literature. Instead, participants appeared to solve the task by exploiting surface distinctions between legal and illegal sequences, and applying strategies such as counting or repetition detection. We suggest alternative interpretations for the observed activation of Broca's area, in terms of the application of calculation rules or of a differential role of working memory. We claim that the learnability of hierarchical embeddings in AGL tasks remains to be demonstrated.     

Understanding the search for meaning in life: personality, cognitive style, and the dynamic between seeking and experiencing meaning.

Although several theories assert that understanding the search for meaning in life is important, empirical research on this construct is sparse. Three studies provide the first extensive effort to understand the correlates of the search for meaning in a multistudy research program. Assessed were relations between search for meaning and well-being, cognitive style, and the Big Five, Big Three, Approach/Avoidance, and Interest models of personality, with a particular emphasis on understanding the correlates of search for meaning that are independent of presence of meaning. Conceptual models of the relation between search and presence were tested. Findings suggest that people lacking meaning search for it; the search for meaning did not appear to lead to its presence. Study 3 found that basic motive dispositions moderated relations between search for meaning and its presence. Results highlight the importance of basic personality dispositions in understanding the search for meaning and its correlates.     

Working memory retention systems: a state of activated long-term memory

High temporal resolution event-related brain potential and electroencephalographic coherence studies of the neural substrate of short-term storage in working memory indicate that the sustained coactivation of both prefrontal cortex and the posterior cortical systems that participate in the initial perception and comprehension of the retained information are involved in its storage. These studies further show that short-term storage mechanisms involve an increase in neural synchrony between prefrontal cortex and posterior cortex and the enhanced activation of long-term memory representations of material held in short-term memory. This activation begins during the encoding/comprehension phase and evidently is prolonged into the retention phase by attentional drive from prefrontal cortex control systems. A parsimonious interpretation of these findings is that the long-term memory systems associated with the posterior cortical processors provide the necessary representational basis for working memory, with the property of short-term memory decay being primarily due to the posterior system. In this view, there is no reason to posit specialized neural systems whose functions are limited to those of short-term storage buffers. Prefrontal cortex provides the attentional pointer system for maintaining activation in the appropriate posterior processing systems. Short-term memory capacity and phenomena such as displacement of information in short-term memory are determined by limitations on the number of pointers that can be sustained by the prefrontal control systems.     

Neural blackboard architectures of combinatorial structures in cognition

Human cognition is unique in the way in which it relies on combinatorial (or compositional) structures. Language provides ample evidence for the existence of combinatorial structures, but they can also be found in visual cognition. To understand the neural basis of human cognition, it is therefore essential to understand how combinatorial structures can be instantiated in neural terms. In his recent book on the foundations of language, Jackendoff described four fundamental problems for a neural instantiation of combinatorial structures: the massiveness of the binding problem, the problem of 2, the problem of variables, and the transformation of combinatorial structures from working memory to long-term memory. This paper aims to show that these problems can be solved by means of neural "blackboard" architectures. For this purpose, a neural blackboard architecture for sentence structure is presented. In this architecture, neural structures that encode for words are temporarily bound in a manner that preserves the structure of the sentence. It is shown that the architecture solves the four problems presented by Jackendoff. The ability of the architecture to instantiate sentence structures is illustrated with examples of sentence complexity observed in human language performance. Similarities exist between the architecture for sentence structure and blackboard architectures for combinatorial structures in visual cognition, derived from the structure of the visual cortex. These architectures are briefly discussed, together with an example of a combinatorial structure in which the blackboard architectures for language and vision are combined. In this way, the architecture for language is grounded in perception. Perspectives and potential developments of the architectures are discussed.     

Memory mechanisms supporting syntactic comprehension

Efforts to characterize the memory system that supports sentence comprehension have historically drawn extensively on short-term memory as a source of mechanisms that might apply to sentences. The focus of these efforts has changed significantly in the past decade. As a result of changes in models of short-term working memory (ST-WM) and developments in models of sentence comprehension, the effort to relate entire components of an ST-WM system, such as those in the model developed by Baddeley (Nature Reviews Neuroscience 4: 829–839, 2003) to sentence comprehension has largely been replaced by an effort to relate more specific mechanisms found in modern models of ST-WM to memory processes that support one aspect of sentence comprehension—the assignment of syntactic structure (parsing) and its use in determining sentence meaning (interpretation) during sentence comprehension. In this article, we present the historical background to recent studies of the memory mechanisms that support parsing and interpretation and review recent research into this relation. We argue that the results of this research do not converge on a set of mechanisms derived from ST-WM that apply to parsing and interpretation. We argue that the memory mechanisms supporting parsing and interpretation have features that characterize another memory system that has been postulated to account for skilled performance—long-term working memory. We propose a model of the relation of different aspects of parsing and interpretation to ST-WM and long-term working memory.     

A functionalistic approach to memory: theory and data

The purpose of this article is to propose a conceptual frame of reference for memory research on the basis of two recent lines of development. One such key development is that of a functional orientation of memory research focusing on processing and function rather than structure and memory entities. The other line of development concerns information storage as distributed rather than localized. A functionalistic frame of reference involving a notion of distributed storage is proposed. According to this view remembering is seen as an interaction between available cognitive capabilities and demands of the task in which the individual is remembering something. Encoding is conceived of as an interaction between "affordances" of the environment and "functional dispositions" of the individual. Retrieval is seen as a re-activation of functional dispositions. The formation of unique combinations of functional dispositions plays a crucial role in obtaining perfect recall performance. The viability of the overall conceptual framework is demonstrated in three experimental studies. The development of the design and procedure for these experiments was a second purpose of this paper, namely to outline an experimental setting which could serve as a complement to computer simulations in studying notions of distributed storage.     

Introspection, consciousness, and human information processing

The paper tries, on rational and empirical grounds, to sketch a theory of introspective awareness, considered as an essential aspect of what is usually talked about in terms of "consciousness". The main thesis is that introspective awareness has an important role of play in human information processing. An attempt is made to clarify the connections between introspective awareness, selective attention, and short-term memory. A lot of human information processing goes on pre-attentively, "automatically", without the involvement of introspective awareness. What is introspectively attended to enters short-term memory, where it remains available for various kinds of mental operations; certain kinds of such operations are themselves introspectively accessible, and may become contents of short-term memory, where they in turn can be operated upon, and hence be modified voluntarily by the subject. Finally, various kinds of limitations to introspective awareness are discussed.     

Verb semantic structures in memory for sentences: Evidence for componential representation

This research contrasts two hypotheses concerning componential storage of meaning. The Complexity Hypothesis assumed by Fodor (The language of thought, NY: Crowell, 1975), Kintsch (The representation of meaning in memory, Hillsdale, NJ: Erlbaum, 1974), and Thorndyke (Conceptual complexity and imagery in comprehension and memory. Journal of Verbal Learning and Verbal Behavior, 1975, 14, 359–369) states that a word with many semantic components will require more processing resources, comprehension time, and long-term memory space than a word with few components, and thus will interfere more with memory for surrounding words. This memory prediction was tested against an alternative prediction based on connectivity. The Connectivity Hypothesis views verb semantic structures as frames for sentence representation and states that memory strength between two nouns in a sentence increases with the number of underlying verb subpredicates that connect the nouns. Thus, the Complexity Hypothesis predicts that a verb with many subpredicates will lead to poorer memory strength between the surrounding nouns than a verb with few subpredicates, while the Connectivity Hypothesis predicts that verbs with many subpredicates will lead to greater memory strength between nouns in cases when the additional subpredicates provide semantic connections between the nouns.In three experiments, subjects recalled subject-verb-object sentences, given subject nouns as cues. General verbs, with relatively few subpredicates, were compared with more specific verbs whose additional subpredicates either did or did not provide additional connections between the surrounding nouns. The level of recall of the object noun, given the subject noun as cue, was predicted by the relative number of connecting subpredicates in the verb, but not by the relative number of subpredicates. This finding supports the Connectivity Hypothesis over the Complexity Hypothesis. These results are interpreted in terms of a model in which the verb conveys a structured set of subpredicates that provides a connective framework for sentence memory.     

Different importance of the volatile and non-volatile fractions of an olfactory signature for individual social recognition in rats versus mice and short-term versus long-term memory

When tested in the olfactory cued social recognition/discrimination test, rats and mice differ in their retention of a recognition memory for a previously encountered conspecific juvenile: Rats are able to recognize a given juvenile for approximately 45 min only whereas mice show not only short-term, but also long-term recognition memory (≥ 24 h). Here we modified the social recognition/social discrimination procedure to investigate the neurobiological mechanism(s) underlying the species differences. We presented a conspecific juvenile repeatedly to the experimental subjects and monitored the investigation duration as a measure for recognition. Presentation of only the volatile fraction of the juvenile olfactory signature was sufficient for both short- and long-term recognition in mice but not rats. Applying additional volatile, mono-molecular odours to the "to be recognized" juveniles failed to affect short-term memory in both species, but interfered with long-term recognition in mice. Finally immunocytochemical analysis of c-Fos as a marker for cellular activation, revealed that juvenile exposure stimulated areas involved in the processing of olfactory signals in both the main and the accessory olfactory bulb in mice. In rats, we measured an increased c-Fos synthesis almost exclusively in cells of the accessory olfactory bulb. Our data suggest that the species difference in the retention of social recognition memory is based on differences in the processing of the volatile versus non-volatile fraction of the individuals' olfactory signature. The non-volatile fraction is sufficient for retaining a short-term social memory only. Long-term social memory - as observed in mice - requires a processing of both the volatile and non-volatile fractions of the olfactory signature.     

Long-term associative learning predicts verbal short-term memory performance

Studies using tests such as digit span and nonword repetition have implicated short-term memory across a range of developmental domains. Such tests ostensibly assess specialized processes for the short-term manipulation and maintenance of information that are often argued to enable long-term learning. However, there is considerable evidence for an influence of long-term linguistic learning on performance in short-term memory tasks that brings into question the role of a specialized short-term memory system separate from long-term knowledge. Using natural language corpora, we show experimentally and computationally that performance on three widely used measures of short-term memory (digit span, nonword repetition, and sentence recall) can be predicted from simple associative learning operating on the linguistic environment to which a typical child may have been exposed. The findings support the broad view that short-term verbal memory performance reflects the application of long-term language knowledge to the experimental setting.     

Disruption of comprehension by the meaning of irrelevant sound

This study investigates the claim that the disruption of comprehension by irrelevant sound is qualitatively different from that of short-term memory for order. Both meaningful and meaningless speech disrupted the comprehensive aspect of the task, but the effect of meaningful speech was significantly greater. Both rehearsal and semantic processing, which are involved in reading comprehension, seem to be susceptible to disruption by irrelevant meaningful speech. The study provides some evidence to suggest that the presence of meaning in the irrelevant sound in creases disruption of performance in cognitive tasks that also call upon processing of meaning.     

A discrimination analysis of training-structure effects on stimulus equivalence outcomes.

Experiments designed to establish stimulus equivalence classes frequently produce differential outcomes that may be attributable to training structure, defined as the order and arrangement of baseline conditional discrimination training trials. Several possible explanations for these differences have been suggested. Here we develop a hypothesis based on an analysis of the simple simultaneous and successive discriminations embedded in conditional discrimination training and testing within each of the training structures that are typically used in stimulus equivalence experiments. Our analysis shows that only the comparison-as-node (many-to-one) structure presents all the simple discriminations in training that are subsequently required for consistently positive outcomes on all tests for the properties of equivalence. The sample-as-node (one-to-many) training structure does not present all the simple discriminations required for positive outcomes on either the symmetry or combined transitivity and symmetry (equivalence) tests. The linear-series training structure presents all the simple discriminations required for consistently positive outcomes on tests for symmetry, but not for symmetry and transitivity combined (equivalence) or transitivity alone. Further, the difference in the number of simple discriminations presented in comparison-as-node training versus the other training structures is larger when the intended class size is greater than three or the number of classes is larger than two. We discuss the relevance of this analysis to interpretations of stimulus equivalence research, as well as some methodological and theoretical implications.     

Disruption of comprehension by the meaning of irrelevant sound

This study investigates the claim that the disruption of comprehension by irrelevant sound is qualitatively different from that of short-term memory for order. Both meaningful and meaningless speech disrupted the comprehensive aspect of the task, but the effect of meaningful speech was significantly greater. Both rehearsal and semantic processing, which are involved in reading comprehension, seem to be susceptible to disruption by irrelevant meaningful speech. The study provides some evidence to suggest that the presence of meaning in the irrelevant sound in creases disruption of performance in cognitive tasks that also call upon processing of meaning.     

Literal meaning, conventional meaning and first meaning

Literal meaning is often identified with conventional meaning. In A Nice Derangement of Epitaphs Donald Davidson argues (1) that literal meaning is distinct from conventional meaning, and (2) that literal meaning is identical to what he calls first meaning. In this paper it is argued that Davidson has established (1) but not (2), that he has succeeded in showing that there is a distinction between literal meaning and conventional meaning but has failed to see that literal meaning and first meaning are also distinct. This failure is somewhat surprising, since it is through a consideration of Davidson's notion of radical interpretation that the distinction between literal meaning and first meaning becomes apparent.I am grateful to the Social Sciences and Humanities Research Council of Canada for its financial support, and to Mark Mercer, Tom Patton and Gary Wedeking for their helpful comments. I would also like to thank David Checkland, who discussed A Nice Derangement of Epitaphs with me at length some years ago.     

Context and homograph meaning resolution.

We describe an activation-based model of word recognition and apply it to the process of resolving the meaning of homographs presented in context. The interpretation of homographs was assessed by asking participants to decide whether a target word was related to the meaning of a sentence containing a homograph. These relatedness decisions varied systematically with the relative frequency of the homograph meanings, delay, and the nature of the sentence context. In the model, it was assumed that orthographic and contextual information combine additively to determine the activation of word meanings, and that the probability of a "related" response is determined by the activation level of the related meaning. The model accurately accounts for all observed effects, as well as their interaction. We conclude that the core process of lexical ambiguity resolution may be quite simple.