1,721,156 research outputs found
A computational model of language functions in flexible goal-directed behaviour
No full textThe function of language in high-order goal-directed human cognition is an important topic at the centre of current debates. Experimental evidence shows that inner speech, representing a self-directed form of language, empowers cognitive processes such as working memory, perception, categorization, and executive functions. Here we study the relations between inner speech and processes like feedback processing and cognitive flexibility. To this aim we propose a computational model that controls an artificial agent who uses inner speech to internally manipulate its representations. The agent is able to reproduce human behavioural data collected during the solution of the Wisconsin Card Sorting test, a neuropsychological test measuring cognitive flexibility, both in the basic condition and when a verbal shadowing protocol is used. The components of the model were systematically lesioned to clarify the specific impact of inner speech on the agent’s behaviour. The results indicate that inner speech improves the efficiency of internal representation manipulation. Specifically, it makes the representations linked to specific visual features more disentangled, thus improving the agent’s capacity to engage/disengage attention on stimulus features after positive/negative action outcomes. Overall, the model shows how inner speech could improve goal-directed internal manipulation of representations and enhance behavioural flexibility
Two-phase galaxy formation: the evolutionary properties of galaxies
Full text linkWe use our model for the formation and evolution of galaxies within a two-phase galaxy formation scenario, showing that the high-redshift domain typically supports the growth of spheroidal systems, whereas at low redshifts the predominant baryonic growth mechanism is quiescent and may therefore support the growth of a disc structure. Under this framework, we investigate the evolving galaxy population by comparing key observations at both low and high redshifts, finding generally good agreement. By analysing the evolutionary properties of this model, we are able to recreate several features of the evolving galaxy population with redshift, naturally reproducing number counts of massive star-forming galaxies at high redshifts, along with the galaxy scaling relations, star formation rate density and evolution of the stellar mass function. Building upon these encouraging agreements, we make model predictions that can be tested by future observations. In particular, we present the expected evolution to z = 2 of the supermassive black hole mass function, and we show that the gas fraction in galaxies should decrease with increasing redshift in a mass, with more and more evolution going to higher and higher masses. Also, the characteristic transition mass from a disc to bulge-dominated system should decrease with increasing redshift
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
A computational model of inner speech supporting flexible goal-directed behaviour in Autism
No full textExperimental and computational studies propose that inner speech boosts categorisation skills and executive functions, making human behaviour more focused and flexible. In addition, many clinical studies highlight a relationship between poor inner-speech and an executive impairment in autism spectrum condition (ASC), but contrasting findings are reported. Here we directly investigate the latter issue through a previously implemented and validated computational model of the Wisconsin Cards Sorting Tests. In particular, the model was applied to explore potential individual differences in cognitive flexibility and inner speech contribution in autistic and neurotypical participants. Our model predicts that the use of inner-speech could increase along the life-span of neurotypical participants but would be reduced in autistic ones. Although we found more attentional failures (i.e., wrong behavioural rule switches) in autistic children/teenagers and more perseverative behaviours in autistic young/older adults, only autistic children and older adults exhibited a lower performance (i.e., fewer consecutive correct rule switches) than matched control groups. Overall, our results corroborate the idea that the reduced use of inner speech could represent a disadvantage for autistic children and autistic older adults. Moreover, the results suggest that cognitive-behavioural therapies should focus on developing inner speech skills in autistic children as this could provide cognitive support throughout their whole life span
Exploring Supermassive Black Hole Growth with ALMA
No full textMassive tori with ≈108-109 M☉ are predicted to extend on a ~100 pc scale around the center of elliptical galaxy progenitors by a model of a supermassive black hole (SMBH) growth coeval to the spheroidal population of the host galaxy. Direct detection of such massive tori would cast light on a key physical condition that allows the rapid growth of SMBHs and the appearance of QSOs at high redshift. For this reason, we examine the detectability of such structures at substantial redshift with the Atacama Large Millimeter Array (ALMA). We propose that submillimeter galaxies (SMGs) are the best targets to test our predictions. In order to assess the observational feasibility, we estimate the expected number counts of SMGs with massive tori and check the detectability with the ALMA instrument, the unique facility which can resolve the central region of high-redshift objects. Our work shows that ALMA will be able to resolve and detect high-J (J > 4) CO emissions from ~100 pc scale extended massive tori up to z ≈ 2. Observations of lensed SMGs will yield excellent spatial resolution, allowing us to resolve their massive tori at even higher redshift. We further discuss the detectability of the HCN molecule as a better tracer of the high-density gas expected in such tori. The final goal of these kind of observations is to pinpoint possible physical mechanisms for storing very large amounts of gas in the very central galactic regions on timescales of several 108 yr
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Two-phase galaxy formation
Full text linkWe propose and test a scenario for the assembly and evolution of luminous matter in galaxies which substantially differs from that adopted by other semi-analytic models. As for the dark matter, we follow the detailed evolution of haloes within the canonical Λ cold dark matter cosmology using standard Monte Carlo methods. However, when overlaying prescriptions for baryon evolution, we take into account an effect pointed out in the past few years by a number of studies mostly based on intensive N-body simulations, namely that typical halo growth occurs in two phases: an early, fast collapse phase featuring several major merger events, followed by a late, quiescent accretion on to the halo outskirts. We propose that the two modes of halo growth drive two distinct modes for the evolution of baryonic matter, favouring the development of the spheroidal and disc components of galaxies, respectively. We test this idea using the semi-analytic technique. Our galaxy formation model envisages an early coevolution of spheroids and the central supermassive black holes, already tested in our previous works, followed by a relatively quiescent growth of discs around the preformed spheroids. In this exploratory study, we couple our model with the spectrophotometric code GRASIL, and compare our results on several properties of the local galaxy population with observations, finding an encouraging agreement
Gravitational lensing of extended high-redshift sources by dark matter haloes
Full text linkHigh-redshift galaxies and quasi-stellar objects (QSOs) are most likely to be strongly lensed by intervening haloes between the source and the observer. In addition, a large fraction of lensed sources is expected to be seen in the submillimetre region, as a result of the enhanced magnification bias on the steep intrinsic number counts. We extend in three directions Blain's earlier study of this effect. First, we use a modification of the Press-Schechter mass function and detailed lens models to compute the magnification probability distribution. We compare the magnification cross-sections of populations of singular isothermal spheres and Navarro, Frenk & White (NFW) haloes and find that they are very similar, in contrast to the image-splitting statistics which were recently investigated in other studies. The distinction between the two types of density profile is therefore, irrelevant for our purposes. Secondly, we discuss quantitatively the maximum magnification, mu(max), that can be achieved for extended sources (galaxies) with realistic luminosity profiles, taking into account the possible ellipticity, of the lensing potential. We find that mu(max) plausibly falls into the range 10-30 for sources of 1-10 h(-1) kpc effective radius at redshifts within 1-4. Thirdly, we apply our model for the lensing magnification to a class of sources following the luminosity, evolution typical for a unified scheme of QSO formation. As a result of the peculiar steepness of their intrinsic number counts, we find that the lensed source counts at a fiducial wave length of 850 mum can exceed the unlensed counts by several orders of magnitude at flux densities greater than or similar to100 mJy, even with a conservative choice of the maximum magnification
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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