Parsing recursive sentences with a connectionist model including a neural stack and synaptic gating.

It is supposed that humans are genetically predisposed to be able to recognize sequences of context-free grammars with centre-embedded recursion while other primates are restricted to the recognition of finite state grammars with tail-recursion. Our aim was to construct a minimalist neural network that is able to parse artificial sentences of both grammars in an efficient way without using the biologically unrealistic backpropagation algorithm. The core of this network is a neural stack-like memory where the push and pop operations are regulated by synaptic gating on the connections between the layers of the stack.

The neuronal replicator hypothesis.

We propose that replication (with mutation) of patterns of neuronal activity can occur within the brain using known neurophysiological processes. Thereby evolutionary algorithms implemented by neuro- nal circuits can play a role in cognition. Replication of structured neuronal representations is assumed in several cognitive architectures.

Analysis of dark albedo features on a southern polar dune field of Mars.

We observed 20-200 m sized low-albedo seepage-like streaks and their annual change on defrosting polar dunes in the southern hemisphere of Mars, based on the Mars Orbiter Camera (MOC), High Resolution Stereo Camera (HRSC), and High Resolution Imaging Science Experiment (HiRISE) images. The structures originate from dark spots and can be described as elongated or flowlike and, at places, branching streaks. They frequently have another spotlike structure at their end.

Bayesian learning of visual chunks by human observers.

Efficient and versatile processing of any hierarchically structured information requires a learning mechanism that combines lower-level features into higher-level chunks. We investigated this chunking mechanism in humans with a visual pattern-learning paradigm. We developed an ideal learner based on Bayesian model comparison that extracts and stores only those chunks of information that are minimally sufficient to encode a set of visual scenes.

The rise of non-adaptive intelligence in humans under pathogen pressure.

Cleverness made our species the most successful primate on Earth, thus claiming that human intelligence is adaptive sounds to be a triviality. Not surprisingly, when establishing long-lasting pair-bonds, humans exhibit mate preferences in favour of clever partners, apparently to increase the chance that their offspring will be as clever as possible. Contrary to this well-established view, here I argue that the adaptive nature of human intelligence has never been proven in a strict evolutionary sense.

Coevolution of metabolic networks and membranes: the scenario of progressive sequestration.

Many regard metabolism as one of the central phenomena (or criteria) of life. Yet, the earliest infrabiological systems may have been devoid of metabolism: such systems would have been extreme heterotrophs. We do not know what level of complexity is attainable for chemical systems without enzymatic aid.

Selective scenarios for the emergence of natural language.

The recent blossoming of evolutionary linguistics has resulted in a variety of theories that attempt to provide a selective scenario for the evolution of early language. However, their overabundance makes many researchers sceptical of such theorising. Here, we suggest that a more rigorous approach is needed towards their construction although, despite justified scepticism, there is no agreement as to the criteria that should be used to determine the validity of the various competing theories.

The evolution of replicators.

Replicators of interest in chemistry, biology and culture are briefly surveyed from a conceptual point of view. Systems with limited heredity have only a limited evolutionary potential because the number of available types is too low. Chemical cycles, such as the formose reaction, are holistic replicators since replication is not based on the successive addition of modules.

Simulating dynamical features of escape panic.

One of the most disastrous forms of collective human behaviour is the kind of crowd stampede induced by panic, often leading to fatalities as people are crushed or trampled. Sometimes this behaviour is triggered in life-threatening situations such as fires in crowded buildings; at other times, stampedes can arise during the rush for seats or seemingly without cause. Although engineers are finding ways to alleviate the scale of such disasters, their frequency seems to be increasing with the number and size of mass events.

The major evolutionary transitions.

There is no theoretical reason to expect evolutionary lineages to increase in complexity with time, and no empirical evidence that they do so. Nevertheless, eukaryotic cells are more complex than prokaryotic ones, animals and plants are more complex than protists, and so on. This increase in complexity may have been achieved as a result of a series of major evolutionary transitions.