The role of learning in risk-avoidance strategies during spider–ant interactions

Cognitive abilities used by arthropods, particularly predators, when interacting in a natural context have been poorly studied. Two neotropical sympatric predators, the golden silk spider Nephila clavipes and the ectatommine ant Ectatomma tuberculatum, were observed in field conditions where their interactions occurred regularly due to the exploitation of the same patches of vegetation. Repeated presentations of E. tuberculatum workers ensnared in their web triggered a progressive decrease in the capture response of N. clavipes. All the spiders that stopped trying to catch the ant on the second and/or third trial were individuals that had been bitten during a previous trial. Behavioural tests in natural field conditions showed that after a single confrontation with ant biting, spiders were able to discriminate this kind of prey more quickly from a defenceless prey (fruit flies) and to selectively and completely suppress their catching response. This one-trial aversive learning was still effective after 24 h. Likewise, E. tuberculatum workers entangled once on a N. clavipes web and having succeeded in escaping, learned to escape more quickly, breaking through the web by preferentially cutting spiral threads (sticky traps) rather than radial threads (stronger structural unsticky components) or pursuing the cutting of radials but doing it more quickly. Both strategies, based on a one-trial learning capability, obviously minimize the number of physical encounters between the two powerful opponents and may enhance their fitness by diminishing the risk of potential injuries resulting from predatory interactions.     

Embodied perception of reachable space: how do we manage threatening objects?

This study aimed at determining whether the size of reachable space is affected by the level of danger of some everyday manipulable objects. Two possibilities are examined: Dangerous objects affect the size of reachable space because of long-term semantic knowledge of their potential hurtful value or the on-line relation between objects’ dangerous attributes and the body. The experimental paradigm combined the danger value (dangerous/not dangerous) and the orientation of objects (e.g. pointing away from/towards the perceiver). Reachability judgments measured the size of peripersonal space, and perception of objects’ danger was estimated through questionnaires. Results revealed that, whatever the estimated level of objects’ danger, the extent of peripersonal space was reduced when the threatening part of dangerous objects was oriented towards participants, not when oriented away. This suggests that the characteristics of the here and now body-objects interaction are crucial in affecting the boundary of peripersonal space.     

Under what conditions would people be willing to make a living organ donation?

The aim was to examine the factors involved in people's willingness to make a living organ donation. A convenience sample of 200 people in southern France rated willingness to be a living donor in 48 scenarios consisting of all combinations of five factors: recipient's identity (close family member and city resident); donor's surgical risk (little and some); donor's possible long-term health consequences (none, some lessening over time, and durable); transplant success ("generally durably successful" and "durably successful one time out of two"); and likelihood of other donors (subject is one of the rare compatible donors or one among others). Cluster analyses showed the existence of three distinct organ donation philosophies. For the largest cluster (49% of participants), willingness to donate was very high to a family member, but low to a city resident. For the second cluster (37%), willingness was high to family, but also moderately high to a city resident. For the third cluster (14%), willingness was always low. Thus, most participants judged themselves ready to make a living organ donation to a family member and many even to a stranger.     

Learned irrelevance: A contemporary overview

This article reviews the recent literature on the topic of learned irrelevance. It asks whether the retardation of subsequent conditioning produced by uncorrelated preexposure is indeed the result of the animal learning that a conditioned stimulus (CS) and unconditioned stimulus (US) are unrelated, or whether it is better explained either as a result of the context specificity of latent inhibition, or as some other artefact of the uncorrelated schedule employed. The conclusion is that there is as yet no good evidence to support the existence of a “genuine” learned irrelevance effect.     

Divide and Rule Better: On Subsidiarity,Legitimacy and the Epistemic Aim of Political Decision‐Making

How should a political society be structured so as to legitimately distribute political power? One principle advanced to answer this question is the principle of subsidiarity. According to this principle, the default locus of political power is with the lowest competent political unit. This article argues that subsidiarity is a structural principle of a conception of political legitimacy informed by epistemic considerations. Broadly, the argument is that political societies organised according to the principle of subsidiarity can more effectively achieve political decisions that can justifiably appear to be correct from the point of view of those subject to them. The article presents two considerations in order to establish a pro tanto case for acting separately before presenting five additional epistemic considerations that establish a prima facie case for acting separately. The article then shows that political legitimacy and the epistemic aim of decision‐making can sometimes be served more effectively and efficiently by allowing higher‐level political units to assist lower‐level political units.     

Analysis of the learned irrelevance effect in appetitive Pavlovian conditioning

In Experiments 1 and 2 rats received uncorrelated presentations of a light conditioned stimulus (CS) and a food unconditioned stimulus (US) on each day of a preexposure phase. Control subjects received the same number of USs during the first half of preexposure and the same number of CSs during the second. Uncorrelated preexposure retarded inhibitory conditioning. Experiment 3 showed, however, that the different patterns of US preexposure experienced by the two groups could in itself influence the course of subsequent inhibitory conditioning. When this factor was equated by restricting the uncorrelated treatment to the first half of the pre-exposure phase (Experiment 2) or by extending the control treatment throughout the phase (Experiment 4) it was found that uncorrelated preexposure retarded excitatory conditioning, but facilitated inhibitory conditioning. This outcome challenges an interpretation in terms of the concept of learned irrelevance, which predicts that uncorrelated preexposure should retard both forms of conditioning.