The potential power of experience in communications of expert consensus levels

Understanding the scientific consensus on anthropogenic climate change has been dubbed a ‘gateway belief’ to engaging people in sustainable behaviour. We consider the question of how the impact of a consensus communication can be maximised. Firstly, the credibility of the communicator should be maximised. One way of achieving this is to present the opinions of a sample of scientists directly to individuals. The decision-making literature suggests that such a technique will confer an additional advantage over standard descriptions of consensus (e.g. ‘97% of scientists agree’). In decision-making research, low probabilities tend to be overweighted when probabilities are described, but underweighted when probability information is experienced. Consequently, statements of high consensus may lead to an overweighting of the dissensus, a phenomenon that may be reversed were the consensus to be ‘experienced.’ We obtain some positive support for our proposal that consensus is best ‘experienced’ in one of two experiments. We suggest that the lack of stronger positive support could relate to ceiling effects for the topics studied and propose that investigation of effective methods for ‘experiencing’ the consensus is a fruitful area for future research

Unrealistic optimism about future life events: a cautionary note

A robust finding in social psychology is that people judge negative events as less likely to happen to themselves than to the average person, a behavior interpreted as showing that people are “unrealistically optimistic” in their judgments of risk concerning future life events. However, we demonstrate how unbiased responses can result in data patterns commonly interpreted as indicative of optimism for purely statistical reasons. Specifically, we show how extant data from unrealistic optimism studies investigating people's comparative risk judgments are plagued by the statistical consequences of sampling constraints and the response scales used, in combination with the comparative rarity of truly negative events. We conclude that the presence of such statistical artifacts raises questions over the very existence of an optimistic bias about risk and implies that to the extent that such a bias exists, we know considerably less about its magnitude, mechanisms, and moderators than previously assumed

What does it mean to be biased: rationality and motivated reasoning

Book synopsis: Psychology of Learning and Motivation publishes empirical and theoretical contributions in cognitive and experimental psychology, ranging from classical and instrumental conditioning to complex learning and problem solving

Bayesian rationality in evaluating multiple testimonies: Incorporating the role of coherence.

Routinely in day-to-day life, as well as in formal settings such as the courtroom, people must aggregate information they receive from different sources. One intuitively important but underresearched factor in this context is the degree to which the reports from different sources fit together, that is, their coherence. The authors examine a version of Bayes’ theorem that not only includes factors such as prior beliefs and witness reliability, as do other models of information aggregation, but also makes transparent the effect of the coherence of multiple testimonies on the believability of the information. The results suggest that participants are sensitive to all the normatively relevant factors when assessing the believability of a set of witness testimonies

Measuring the viscosity of lava in the field:A review

Many scientists who have worked on active lava flows or attempted to model lava flows have recognized the importance of rheology in understanding flow dynamics. Numerous attempts have been made to estimate viscosity using flow velocities in active lava channels. However, this only gives a bulk or mean value, applies to channelized flow, and the need to estimate flow depth leads to a large degree of uncertainty. It is for this reason that some scientists have resorted to more direct methods for measuring the lava viscosity in the field. Initial attempts used crude instruments (such as forcing a rod into a flow using the operators body-weight), and even the latest instruments (motor-driven rotational viscometer) are significantly less refined than those one would encounter in a well-equipped laboratory. However, if suitable precautions are taken during instrument design, deployment in the field and post-processing of data, the results form an extremely valuable set of measurements that can be used to model and understand the complex rheological behavior of active lava flows. As far as we are aware, eleven field measurements of lava rheology have been published; the first took place in 1948, and the latest (at the time of writing) in 2016. Two types of instrument have been used: penetrometers and rotational viscometers. Penetrometers are suitable for relatively high viscosity (10 4–10 6 Pa s) lava flows, but care has to be taken to ensure that the sensor is at lava temperature and measurements are not affected by the resistance of outer cooled crust. Rotational viscometers are the most promising instruments at lower viscosities (1–10 4 Pa s) because they can operate over a wider range of strain rates permitting detailed flow curves to be calculated. Field conditions are challenging and measurements are not always possible as direct approach to and contact with active lava is necessary. However it is currently the only way to capture the rheology of lava in its natural state. Such data are fundamental if we are to adequately model and understand the complex behavior of active lava flows

'Damned by faint praise': a Bayesian account

“Damned by Faint Praise” is the phenomenon whereby weak positive information leads to a negative change in belief. However, in a Bayesian model of belief revision positive information can seemingly only exert a positive change in belief. We introduce a version of Bayes’ Theorem incorporating the concept of epistemic closure. This reformalization is able to predict the conditions under which a ‘damned by faint praise’ effect is observed. Moreover, good, parameter-free fits are observed between the Bayesian model and the experimental data. This provides further support for the Bayesian approach to informal argumentation (e.g., Hahn & Oaksford, 2007)

Conservatism in belief revision and participant skepticism

Comparing the responses of participants in reasoning experiments to the normative standard of Bayes’ Theorem has been a popular empirical approach for almost half a century. One longstanding finding is that people’s belief revision is conservative with respect to the normative prescriptions of Bayes’ Theorem, that is, beliefs are revised less than they should be. In this paper, we consider a novel explanation of conservatism, namely that participants do not perceive information provided to them in experiments as coming from a fully reliable source. From the Bayesian perspective, less reliable evidence should lead to more conservative belief revision. Thus, there may be less of discrepancy between normative predictions and behavioural data than previously assumed