1,720,991 research outputs found
How training and testing histories affect generalization: a test of simple neural networks
No full textWe show that a simple network model of associative learning can\ud
reproduce three findings that arise from particular training and\ud
testing procedures in generalization experiments: the effect of 1)\ud
``errorless learning'' and 2) extinction testing on peak shift, and\ud
3) the central tendency effect. These findings provide a true test\ud
of the network model, which was developed to account for other\ud
penhomena, and highlight the potential of neural networks to study\ud
phenomena that depend on sequences of experiences with many stimuli.\ud
Our results suggest that at least some such phenomena, e.g.,\ud
stimulus range effects, may derive from basic mechanisms of\ud
associative memory rather than from more complex memory processes
Cumulative culture and explosive demographic transitions
No full textA demographic transition is a change in the pattern of growth of
a population. Human history records several kinds of such
transitions, e.g., from stability to growth or between different
kinds of growth. Culture is often implied as the main fuel of
demographic transitions, but theorizing is so far limited to
verbal arguments. Here we study two simple formal models in
which population size and the amount of culture in a population
influence each other's dynamics. The first model has two
regimes: an equilibrium regime in which both population size and
amount of culture reach stable values, and an explosive regime
in which both variables increase exponentially without bound. A
transition between these regimes is caused by changes in
parameters that describe the accuracy of cultural transmission
and the interaction between demography and culture. The second
model suggests that a transition from extensive to intensive
accumulation of culture may derive from a qualitative change in
how individuals cooperate to create culture
Culture creates its own rules: the rise of conservatism and persuasion
No full textMany aspects of human behaviour are attributed to culture, but the
extent to which culture is influenced by our genes remains strongly
debated. Cultural evolution has been viewed as
controlled by a genetically determined human
nature, as a distinct process in
interaction with genetic evolution, and as an
autonomous process wholly free from genetic
influences. Proponents of the latter view often
imply that cultural evolution may take any direction, but this is
not necessarily true. Here we show how forces that operate within
culture itself can systematically shape behaviour and personality
traits that have a significant impact on cultural change.
Specifically, we show that both unwillingness to change
(``conservatism'') and influencing others to become like yourself
(``persuasion'') are traits favoured by cultural evolution, even
when individuals have no genetic predisposition towards these
traits
Critical social learning: A solution to Rogers' paradox of non-adaptive culture
No full textWe expand Rogers’ (1988) game theoretical model of the evolution of
social learning considering that 1) individual learning does not always pro-
duce optimal behavior; 2) social learning is not always accurate. Further, we
introduce a “critical social learning” strategy that tries to solve an adaptive
problem first by social learning, and then by individual learning if socially
acquired behavior proves unsatisfactory. This strategy is always superior
to pure social learning and has typically higher fitness than pure individual
learning, providing a solution to Rogers’ paradox of non-adaptive culture.
Critical social learning is an evolutionarily stable strategy (ESS) unless cul-
tural transmission is highly unfaithful, the environment highly variable or
social learning much costlier than individual learning, and quite independent
of the success rate of individual learning. We compare the model to empir-
ical data on social learning and on spatial variation in primate cultures, and
list three requirements for adaptive culture
Signaling
No full textSignaling is an intriguing behavioral phenomenon observed, almost without exception, when organisms
interact. Signaling occurs between a signaler using a display, often conspicuous but sometimes subtle,
and a receiver that perceives the display and then responds. We see signaling between individuals with
common interests, such as bees dancing to inform their sisters about distant food, and between
opponents, such as paper wasps competing over a scrap of food. Signaling is at the center of courtship,
begging, fighting, interactions between flower and pollinator, and between prey and predator.
Sometimes more than one signaler and receiver are involved, such as in various cases of mimicry, in
eavesdropping, or when several males court a female.
This chapter is a review of the theory of signal evolution. We will focus on a few main questions:
- Why is signaling so common, even when signalers and receivers have conflicting interests?
- What information do signals convey?
- What prevents signalers from displaying misleading signals, i.e., from cheating?
- Why do signals look the way they do
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
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
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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