Ensemble coding of faces occurs in children and develops dissociably from coding of individual faces

Ensemble coding allows adults to access useful information about average properties of groups, sometimes even in the absence of detailed representations of individual group members. This form of coding may emerge early in development with initial reports of ensemble coding for simple properties (size, numerosity) in young children and even infants. Here we demonstrate that ensemble coding of faces, which provides information about average properties of social groups, is already present in 6–8‐year‐old children. This access to average information increases with age from 6 to 18 years and its development is dissociable from age‐related improvements in the coding of individual face identities. This dissociation provides the first direct evidence that distinct processes underlie ensemble and individual coding of face identity, evidence that has been lacking from adult studies. More generally, our results add to the emerging evidence for impressively mature sensitivity to statistical properties of the visual environment in children. They indicate that children have access to gist information about social groups that may facilitate adaptive social behaviour.     

Discrimination nets as psychological models

Simulations of human cognitive processes often employ discrimination nets to model the access of permanent memory. We consider two types of discrimination nets—EPAM and positive-proper-only nets—and argue that they have insufficient psychological validity. Their deficiencies arise from negative properties, insufficient sensitivity to the discriminativeness of properties, extreme sensitivity to missing or incorrect properties, inefficiency in representing multiple knowledge domains, and seriality. We argue that these deficiencies stem from a high degree of test contingency in utilizing property information during acquisition and memory search. Discrimination nets are compared to other models that have less or no test contingency (e.g., PANDEMONIUM) and that thereby avoid the problems of discrimination nets. We propose that understanding test contingency and discovering psychologically valid ways to implement it will be central to understanding and simulating memory indexing in human cognition.     

A practical solution to the pervasive problems of<Emphasis Type="Italic">p</Emphasis> values

In the field of psychology, the practice ofp value null-hypothesis testing is as widespread as ever. Despite this popularity, or perhaps because of it, most psychologists are not aware of the statistical peculiarities of thep value procedure. In particular,p values are based on data that were never observed, and these hypothetical data are themselves influenced by subjective intentions. Moreover,p values do not quantify statistical evidence. This article reviews thesep value problems and illustrates each problem with concrete examples. The three problems are familiar to statisticians but may be new to psychologists. A practical solution to thesep value problems is to adopt a model selection perspective and use the Bayesian information criterion (BIC) for statistical inference (Raftery, 1995). The BIC provides an approximation to a Bayesian hypothesis test, does not require the specification of priors, and can be easily calculated from SPSS output.     

A methodological review of sex-related access discrimination problems

This article provides a comprehensive review of the literature pertaining to sex-related access discrimination problems. The results indicate that positive and negative access discrimination occurs for both males and females. The major variables that appear to account for sex-related access discrimination are the sex role of the position, the amount of job-related information regarding the applicant, and the characteristics of the evaluator population. In general, it appears that the effects of access discrimination can be obfuscated if sufficient information is available regarding job-related variables other than sex. In selected instances, it also appears that populations which have been sensitized to female access discrimination problems may demonstrate reverse discrimination towards women applying for “out-of-role” positions. The article ends with a set of specific hypotheses designed to further investigate and clarify the process of sex-related discrimination in employment situations.     

Some teasers concerning conditional probabilities

A family of notorious teasers in probability is discussed. All ask for the probability that the objects of a certain pair both have some property when information exists that at least one of them does. These problems should be solved using conditional probabilities, but cause difficulties in characterizing the conditioning event appropriately. In particular, they highlight the importance of determining the way information is being obtained. A probability space for modeling verbal problems should allow for the representation of the given outcome and the statistical experiment which yielded it. The paper gives some psychological reasons for the tricky nature of these problems, and some practical tips for handling them.     

Genetic enhancement: plan now to act later

All three main articles in the issues of the Kennedy Institute of Ethics Journal endorse the view that genetic enhancement should be permitted, including human germ-line genetic enhancement. However, unregulated, wealth-based access to genetic enhancement in general, and germ-line enhancement in particular, would create intolerable risks for society. Although there are a number of practical problems raised by proposals to regulate or restrict access to genetic enhancement, which will make it difficult if not impossible to muster support for any effective restrictions until we begin to experience the societal problems that genetic enhancement will create, it is important to consider now what restrictions would be appropriate, how they would be imposed, and what changes would be needed in existing laws and institutions to facilitate them. Without this type of groundwork, there is no way society will be in a position to act in time.     

Missing data techniques for structural equation modeling

As with other statistical methods, missing data often create major problems for the estimation of structural equation models (SEMs). Conventional methods such as listwise or pairwise deletion generally do a poor job of using all the available information. However, structural equation modelers are fortunate that many programs for estimating SEMs now have maximum likelihood methods for handling missing data in an optimal fashion. In addition to maximum likelihood, this article also discusses multiple imputation. This method has statistical properties that are almost as good as those for maximum likelihood and can be applied to a much wider array of models and estimation methods.     

Modeling cross-situational word-referent learning: prior questions

Both adults and young children possess powerful statistical computation capabilities--they can infer the referent of a word from highly ambiguous contexts involving many words and many referents by aggregating cross-situational statistical information across contexts. This ability has been explained by models of hypothesis testing and by models of associative learning. This article describes a series of simulation studies and analyses designed to understand the different learning mechanisms posited by the 2 classes of models and their relation to each other. Variants of a hypothesis-testing model and a simple or dumb associative mechanism were examined under different specifications of information selection, computation, and decision. Critically, these 3 components of the models interact in complex ways. The models illustrate a fundamental tradeoff between amount of data input and powerful computations: With the selection of more information, dumb associative models can mimic the powerful learning that is accomplished by hypothesis-testing models with fewer data. However, because of the interactions among the component parts of the models, the associative model can mimic various hypothesis-testing models, producing the same learning patterns but through different internal components. The simulations argue for the importance of a compositional approach to human statistical learning: the experimental decomposition of the processes that contribute to statistical learning in human learners and models with the internal components that can be evaluated independently and together.     

From Information‐Seeking Behavior to Meaning Engagement Practice.

We invite readers of this colloquy on information‐seeking behavior to reconsider the worldview that structures scholarly and practical thinking about information‐seeking behavior as a mode of human activity. We propose an alternative formulation–meaning engagement practice–to draw into relief the assumptions that tacitly underpin the investigation of information‐seeking behavior. We develop this alternative by contrasting information with meaning, seeking with engagement, and behavior with practice. By rethinking information‐seeking behavior through the lens of meaning engagement practice, avenues for theoretical development and systematic investigation of communication more generally are recovered. We ground our case for meaning engagement practice in four research contexts: modeling the user in information mediation, information access and browsing as relevant processes for understanding information‐seeking behavior, the products and by‐products of an information‐seeking behavior worldview in psychiatric evaluation, and approaches to the design of mediation practices that encourage reflection.     

Statistical and information properties of head direction cells

The human channel capacity for identifying sensory stimuli is compared with channel capacities based on neurophysiological findings. Studies have shown that cells in the postsubiculum (PoS) and the anterior dorsal thalamus (ADN) of the rat discharge as a function of the animal's head direction in the horizontal plane. We compute the statistical properties of the firing rates of head direction (HD) cells and the potential amount of information transmitted by these cells according to two theoretical models. The ceU response model for single cells indicates that information transmitted is much less than 0.5 bits. The population response model developed for cell ensembles generates values in the range of 1-3.2 bits, suggesting that a cell population can distinguish between two and nine head directions, depending on the value used for the standard deviation of directions over which a cell fires. These values are similar to those found in human psychophysical studies of the channel capacity for unidimensional sensory attributes.     

谈谈中国临床试验研究中受试者权益保障问题

随着国家《药品临床试验管理规范》的颁布与实施,我国新药临床试验研究水平有相当的提高,但也存在着一些问题。其中包括保护受试者权益问题。国家GCP有关章节中明确指出要保护受试者权益。并有具体规定,但在执行中尚有出入,如试验方案未经伦理委员会批准,未向受试者告知试验内容。或告知的不够充分,甚至在未签署知情同意书时就开始试验等。为此,我国采取了相应的措施,如设立药品临床研究培训中心;定期对临床试验基地的研究者以及相关人员如与试验有关的医师,药师及申办者进行GCP培训,基地审核制度,以法律手段来保证受试者权益等。     

The role of movement in the recognition of famous faces

The effects of movement on the recognition of famous faces shown in difficult conditions were investigated. Images were presented as negatives, upside down (inverted), and thresholded. Results indicate that, under all these conditions, moving faces were recognized significantly better than static ones. One possible explanation of this effect could be that a moving sequence contains more static information about the different views and expressions of the face than does a single static image. However, even when the amount of static information was equated (Experiments 3 and 4), there was still an advantage for moving sequences that contained their original dynamic properties. The results suggest that the dynamics of the motion provide additional information, helping to access an established familiar face representation. Both the theoretical and the practical implications for these findings are discussed.     

Neural bases of binocular rivalry

During binocular rivalry, conflicting monocular images compete for access to consciousness in a stochastic, dynamical fashion. Recent human neuroimaging and psychophysical studies suggest that rivalry entails competitive interactions at multiple neural sites, including sites that retain eye-selective information. Rivalry greatly suppresses activity in the ventral pathway and attenuates visual adaptation to form and motion; nonetheless, some information about the suppressed stimulus reaches higher brain areas. Although rivalry depends on low-level inhibitory interactions, high-level excitatory influences promoting perceptual grouping and selective attention can extend the local dominance of a stimulus over space and time. Inhibitory and excitatory circuits considered within a hybrid model might account for the paradoxical properties of binocular rivalry and provide insights into the neural bases of visual awareness itself.     

Statistical inference and sensitivity to sampling in 11-month-old infants

Research on initial conceptual knowledge and research on early statistical learning mechanisms have been, for the most part, two separate enterprises. We report a study with 11-month-old infants investigating whether they are sensitive to sampling conditions and whether they can integrate intentional information in a statistical inference task. Previous studies found that infants were able to make inferences from samples to populations, and vice versa [Xu, F., & Garcia, V. (2008). Intuitive statistics by 8-month-old infants. Proceedings of the National Academy of Sciences of the United States of America, 105, 5012-5015]. We found that when employing this statistical inference mechanism, infants are sensitive to whether a sample was randomly drawn from a population or not, and they take into account intentional information (e.g., explicitly expressed preference, visual access) when computing the relationship between samples and populations. Our results suggest that domain-specific knowledge is integrated with statistical inference mechanisms early in development.     

Toward an appropriate baseline for measures of eye movement behavior during reading

In empirical studies of human eye movement behavior during reading, it is common to compute various summary measures from the data, but these measures are typically not evaluated with respect to corresponding measures of baseline performance. The authors present a method for deriving an appropriate baseline by mapping the actual behavior to a random perturbation of the text being read, and they find surprising similarities between the baseline and the empirical data. The practical message from these findings is that the importance of a particular factor in explaining either empirical or simulated eye movement patterns should be evaluated using an appropriate baseline. In addition to this methodological point, the authors suggest that eye movement behavior in reading may be constrained by the properties of an eye-guidance system that has adapted to the coarse-grained statistical properties of written language.     

Representing Spatial Structure Through Maps and Language: Lord of the Rings Encodes the Spatial Structure of Middle Earth

Spatial mental representations can be derived from linguistic and non‐linguistic sources of information. This study tested whether these representations could be formed from statistical linguistic frequencies of city names, and to what extent participants differed in their performance when they estimated spatial locations from language or maps. In a computational linguistic study, we demonstrated that co‐occurrences of cities in Tolkien’s Lord of the Rings trilogy and The Hobbit predicted the authentic longitude and latitude of those cities in Middle Earth. In a human study, we showed that human spatial estimates of the location of cities were very similar regardless of whether participants read Tolkien’s texts or memorized a map of Middle Earth. However, text‐based location estimates obtained from statistical linguistic frequencies better predicted the human text‐based estimates than the human map‐based estimates. These findings suggest that language encodes spatial structure of cities, and that human cognitive map representations can come from implicit statistical linguistic patterns, from explicit non‐linguistic perceptual information, or from both.     

Experimental tests of the mean-variance model for portfolio selection

Statistically knowledgeable male and female undergraduate students participated in 40 portfolio selection problems with monetary payoff contingent on performance. The portfolio selection task included two independent risky assets with normally distributed returns. It provided access to information about previous returns, allowed borrowing and lending at a fixed interest rate, and forced on each decision period a choice between the two risky assets. The findings show a high percentage of inefficient mean-variance portfolios which does not decrease with practice, a high rate of requests for useless information, a large frequency of switches between the two risky assets, and sequential dependencies. Theoretical and practical implications of the findings are briefly discussed.     

Statistical and information properties of head direction cells

The human channel capacity for identifying sensory stimuli is compared with channel capacities based on neurophysiological findings. Studies have shown that cells in the postsubiculum (PoS) and the anterior dorsal thalamus (ADN) of the rat discharge as a function of the animal’s head direction in the horizontal plane. We compute the statistical properties of the firing rates of head direction (HD) cells and the potential amount of information transmitted by these cells according to two theoretical models. Thecell response model for single cells indicates that information transmitted is much less than 0.5 bits. Thepopulation response model developed for cell ensembles generates values in the range of 1–3.2 bits, suggesting that a cell population can distinguish between two and nine head directions, depending on the value used for the standard deviation of directions over which a cell fires. These values are similar to those found in human psychophysical studies of the channel capacity for unidimensional sensory attributes.     

ASTEF: A simple tool for examining fixations

In human factors and ergonomics research, the analysis of eye movements has gained popularity as a method for obtaining information concerning the operator's cognitive strategies and for drawing inferences about the cognitive state of an individual. For example, recent studies have shown that the distribution of eye fixations is sensitive to variations in mental workload---dispersed when workload is high, and clustered when workload is low. Spatial statistics algorithms can be used to obtain information about the type of distribution and can be applied over fixations recorded during small epochs of time to assess online changes in the level of mental load experienced by the individuals. In order to ease the computation of the statistical index and to encourage research on the spatial properties of visual scanning, A Simple Tool for Examining Fixations has been developed. The software application implements functions for fixation visualization, management, and analysis, and includes a tool for fixation identification from raw gaze point data. Updated information can be obtained online at www.astef.info, where the installation package is freely downloadable.