Symbolic representation of probabilistic worlds

Symbolic representation of environmental variables is a ubiquitous and often debated component of cognitive science. Yet notwithstanding centuries of philosophical discussion, the efficacy, scope, and validity of such representation has rarely been given direct consideration from a mathematical point of view. This paper introduces a quantitative measure of the effectiveness of symbolic representation, and develops formal constraints under which such representation is in fact warranted. The effectiveness of symbolic representation hinges on the probabilistic structure of the environment that is to be represented. For arbitrary probability distributions (i.e., environments), symbolic representation is generally not warranted. But in modal environments, defined here as those that consist of mixtures of component distributions that are narrow ("spiky") relative to their spreads, symbolic representation can be shown to represent the environment with a relatively negligible loss of information. Modal environments support propositional forms, logical relations, and other familiar features of symbolic representation. Hence the assumption that our environment is, in fact, modal is a key tacit assumption underlying the use of symbols in cognitive science.     

What’s magic about magic numbers? Chunking and data compression in short-term memory

Short term memory is famously limited in capacity to Miller's (1956) magic number 7±2-or, in many more recent studies, about 4±1 "chunks" of information. But the definition of "chunk" in this context has never been clear, referring only to a set of items that are treated collectively as a single unit. We propose a new more quantitatively precise conception of chunk derived from the notion of Kolmogorov complexity and compressibility: a chunk is a unit in a maximally compressed code. We present a series of experiments in which we manipulated the compressibility of stimulus sequences by introducing sequential patterns of variable length. Our subjects' measured digit span (raw short term memory capacity) consistently depended on the length of the pattern after compression, that is, the number of distinct sequences it contained. The true limit appears to be about 3 or 4 distinct chunks, consistent with many modern studies, but also equivalent to about 7 uncompressed items of typical compressibility, consistent with Miller's famous magical number.     

Semantic similarity influences early morphological priming in Serbian: A challenge to form-then-meaning accounts of word recognition

Semantically similar (e.g., coolant-COOL) primes have produced greater facilitation than have form-similar but semantically dissimilar (e.g., rampant-RAMP) primes when English words have appeared in the forward-masked primed lexical decision task (Feldman, O'Connor, & Moscoso del Prado Martín, Psychonomic Bulletin & Review 16: 684-691, 2009). These results challenge claims that form-based, semantically blind activation underlies early morphological facilitation. Some have argued that the English materials in previous studies were not ideally constructed, insofar as the types of spelling changes to affixed stems differed in the semantically similar and dissimilar pairs. The present study exploited Serbian's bialphabetism, rich morphology, and homographic (form-identical) stems to replicate early effects of semantic similarity. Furthermore, it incorporated within-target manipulations of prime type and of alphabet, such that the alphabets of the prime-target pairs matched in Experiment 1a and alternated in Experiment 1b. Importantly, no letter or phoneme changes occurred between the stems of the primes and targets. These results revealed significant effects of semantic similarity that are comparable with and without alphabet alternation. The semantic effects in Serbian replicated almost exactly those in English (Feldman et al., Psychonomic Bulletin & Review 16: 684-691, 2009), which suggests that even early in the course of processing, morphemes are units of meaning as well as of form. The results failed to support models of lexical processing that postulate sequential access, first to the morphological form, and then to the semantic aspects of words.     

Affective state influences perception by affecting decision parameters underlying bias and sensitivity

Studies of the effect of affect on perception often show consistent directional effects of a person's affective state on perception. Unpleasant emotions have been associated with a "locally focused" style of stimulus evaluation, and positive emotions with a "globally focused" style. Typically, however, studies of affect and perception have not been conducted under the conditions of perceptual uncertainty and behavioral risk inherent to perceptual judgments outside the laboratory. We investigated the influence of perceivers' experienced affect (valence and arousal) on the utility of social threat perception by combining signal detection theory and behavioral economics. We compared 3 perceptual decision environments that systematically differed with respect to factors that underlie uncertainty and risk: the base rate of threat, the costs of incorrect identification threat, and the perceptual similarity of threats and nonthreats. We found that no single affective state yielded the best performance on the threat perception task across the 3 environments. Unpleasant valence promoted calibration of response bias to base rate and costs, high arousal promoted calibration of perceptual sensitivity to perceptual similarity, and low arousal was associated with an optimal adjustment of bias to sensitivity. However, the strength of these associations was conditional upon the difficulty of attaining optimal bias and high sensitivity, such that the effect of the perceiver's affective state on perception differed with the cause and/or level of uncertainty and risk.     

Exploring the mental space of autonomous intentional agents

The ability to infer the intentions of other agents on the basis of their motion is a critical psychological faculty. In the present study, we examine a key question underlying this process, namely: What are the psychologically natural categories of intentional agents and actions? To investigate this question empirically, we use displays containing a number of autonomous, independently programmed agents moving about a two-dimensional environment and interacting with one another. Each agent behaves according to its own simple program, controlled by a small number of parameters that define its "personality." We probe participants' impressions of the similarities among the behaviors of the various agents, and then use multidimensional scaling in an attempt to recover the subjective mental space of agent types. An important variable underlying this space turns out to be a parameter that determines how the agent reacts to a nearby agent at one critical distance. A follow-up experiment suggests that variation along this parameter ultimately contributes to modulating a more fundamental perceptual dimension that reflects how "hostile" or "friendly" the agents appear to be.     

How do within-person changes due to aging affect job performance?

As the mean age of the workforce in industrialized countries trends upward, increasing attention has been paid to group-level differences between younger and older workers in terms of job performance. The present article takes an alternative perspective by examining within-person changes that occur with aging and how the process of aging affects employees' workplace behavior. We begin by highlighting five areas in which we observe major within-person changes related to aging: (1) cognitive capacity, (2) personality, (3) goal orientation, (4) social-emotional experience, and (5) health. Then, we demonstrate why and how these within-person changes due to aging affect core task performance, citizenship behavior, and counterproductive work behavior across the lifespan.     

Psychological stress,appraisal, emotion and Cardiovascular response in a public speaking task

Forty-three undergraduates (30 males, 13 females) prepared and performed a speech task (stressor) or a reading task (no-stressor control). Preparing to speak led to greater threat appraisal, negative emotion, and cardiovascular (CV) response than preparing to read aloud, particularly in speech anxious individuals. Delivering the speech, however, did not result in an increment in CV response over and above preparation. Although threat appraisals could not explain the effect of stress on CV response during task preparation, negative emotion accounted for over half of the effect. These data support the hypothesis that CV response in these studies is at least partially accounted for by psychological processes (stressor-specific anxiety and negative emotional response) and suggests that these processes may be best studied during a period of stressor anticipation.     

let your life speak: assessing the effectiveness of a program to explore meaning,purpose, and calling with college students

Typical career planning courses assist students with the self‐assessment process, career exploration, and decision making. Although this assistance is helpful, college students are increasingly concerned with issues of meaning and calling (P. Braun, 2005). The authors describe and test the effectiveness of the Let Your Life Speak course, a program to help students articulate their framework of life meaning and increase their sense of vocational calling. Results indicate an increase in sense of vocational calling, greater confidence in ability to achieve goals, and a deepened framework of life meaning. Moreover, 96% reported they would recommend the course to others.     

Proof-Theoretic Semantics for Subsentential Phrases

The paper briefly surveys the sentential proof-theoretic semantics for fragment of English. Then, appealing to a version of Frege’s context-principle (specified to fit type-logical grammar), a method is presented for deriving proof-theoretic meanings for sub-sentential phrases, down to lexical units (words). The sentential meaning is decomposed according to the function-argument structure as determined by the type-logical grammar. In doing so, the paper presents a novel proof-theoretic interpretation of simple type, replacing Montague’s model-theoretic type interpretation (in arbitrary Henkin models). The domains of derivations are collections of derivations in the associated “dedicated” natural-deduction proof-system, and functions therein (with no appeal to models, truth-values and elements of a domain). The compositionality of the semantics is analyzed.