433,738 research outputs found
A novel plasticity rule can explain the development of sensorimotor intelligence
Grounding autonomous behavior in the nervous system is a fundamental
challenge for neuroscience. In particular, the self-organized behavioral
development provides more questions than answers. Are there special functional
units for curiosity, motivation, and creativity? This paper argues that these
features can be grounded in synaptic plasticity itself, without requiring any
higher level constructs. We propose differential extrinsic plasticity (DEP) as
a new synaptic rule for self-learning systems and apply it to a number of
complex robotic systems as a test case. Without specifying any purpose or goal,
seemingly purposeful and adaptive behavior is developed, displaying a certain
level of sensorimotor intelligence. These surprising results require no system
specific modifications of the DEP rule but arise rather from the underlying
mechanism of spontaneous symmetry breaking due to the tight
brain-body-environment coupling. The new synaptic rule is biologically
plausible and it would be an interesting target for a neurobiolocal
investigation. We also argue that this neuronal mechanism may have been a
catalyst in natural evolution.Comment: 18 pages, 5 figures, 7 video
Contestable adulthood: variability and disparity in markers for negotiating the transition to adulthood
Recent research has identified a discreet set of subjective markers that are seen as characterizing the transition to adulthood. The current study challenges this coherence by examining the disparity and variability in young peopleâs selection of such criteria. Four sentence-completion cues corresponding to four differentcontexts in which adult status might be contested were given to 156 British 16- to 17-year-olds. Their qualitative responses were analyzed to
explore patterns whilst capturing some of their richness and diversity. An astonishing amount of variability emerged, both within and between cued contexts.The implications of this variability for how the transition to adulthood is experienced are explored. The argument is made that markers of the transition to adulthood are not merely reflective of the bioâpsychoâsocial development of
young people. Rather, adulthood here is seen as an essentially contested concept,located within the discursive interactional environment in which young people participate
Interpretable multiclass classification by MDL-based rule lists
Interpretable classifiers have recently witnessed an increase in attention
from the data mining community because they are inherently easier to understand
and explain than their more complex counterparts. Examples of interpretable
classification models include decision trees, rule sets, and rule lists.
Learning such models often involves optimizing hyperparameters, which typically
requires substantial amounts of data and may result in relatively large models.
In this paper, we consider the problem of learning compact yet accurate
probabilistic rule lists for multiclass classification. Specifically, we
propose a novel formalization based on probabilistic rule lists and the minimum
description length (MDL) principle. This results in virtually parameter-free
model selection that naturally allows to trade-off model complexity with
goodness of fit, by which overfitting and the need for hyperparameter tuning
are effectively avoided. Finally, we introduce the Classy algorithm, which
greedily finds rule lists according to the proposed criterion. We empirically
demonstrate that Classy selects small probabilistic rule lists that outperform
state-of-the-art classifiers when it comes to the combination of predictive
performance and interpretability. We show that Classy is insensitive to its
only parameter, i.e., the candidate set, and that compression on the training
set correlates with classification performance, validating our MDL-based
selection criterion
Outer-totalistic cellular automata on graphs
We present an intuitive formalism for implementing cellular automata on
arbitrary topologies. By that means, we identify a symmetry operation in the
class of elementary cellular automata. Moreover, we determine the subset of
topologically sensitive elementary cellular automata and find that the overall
number of complex patterns decreases under increasing neighborhood size in
regular graphs. As exemplary applications, we apply the formalism to complex
networks and compare the potential of scale-free graphs and metabolic networks
to generate complex dynamics.Comment: 5 pages, 4 figures, 1 table. To appear in Physics Letters
MODERATE SEVERITY DISTURBANCE HAS SIMILAR EFFECTS ON THE PRODUCTION OF THREE FORESTS NESTED WITHIN THE UPPER GREAT LAKES LANDSCAPE
Moderate severity disturbances, which only kill a subset of canopy trees (e.g., via insects, pathogens, and windthrow), are increasingly widespread, and can alter forest structure and production. Whether moderate severity disturbance similarly affects the net primary production (NPP) of different forest stands within inherently heterogeneous landscapes, however, is unknown. We experimentally disturbed three, 2-ha stands varying in forest structure and primary production, reducing stand basal area 38 to 66 % by stem girdling all mature early successional aspen (Populus) and birch (Betula). For nearly a decade, we examined how the forest stands restructured and recovered, and linked post-recovery physical and biological structure with light absorption and wood NPP. Disturbance significantly altered the structure of all stands and prompted a similar decade-long pattern of primary production decline and recovery. All stands exhibited an initial reduction in wood NPP, recovering to, or exceeded pre-disturbance levels within eight years. Following the recovery of wood NPP, more biologically diverse forest canopies with higher leaf area indexes captured more light, and, subsequently, had higher rates of wood NPP. We provide limited support that disturbance may enhance long-term primary production through its effects on canopy structural reorganization. We conclude that, while the forests examined responded similarly to disturbance, improved understanding of different forest ecosystemsâ response to disturbance remains critical to informing carbon management decisions across diverse landscape mosaics
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