The scientific concepts of mental imagery and hallucinations are each used independently of the other in experiments; uses that simultaneously evoke and obscure their historical connections. To highlight one of these connections, I will begin by sketching episodes from the largely separate developmental trajectories of each concept. Considering these historical sketches side-by-side, I will argue that the independent uses of these concepts each inherited a shared set of interdependent associations. In doing so, I seek to illustrate the value of examining historical connections between mental imagery and hallucinations for studying the current uses of these two concepts in neuroimaging experiments.

As replications of individual studies are resource intensive, techniques for predicting the replicability are required. We introduce the repliCATS (Collaborative Assessments for Trustworthy Science) process, a new method for eliciting expert predictions about the replicability of research. This process is a structured expert elicitation approach based on a modified Delphi technique applied to the evaluation of research claims in social and behavioural sciences. The utility of processes to predict replicability is their capacity to test scientific claims without the costs of full replication. Experimental data supports the validity of this process, with a validation study producing a classification accuracy of 84% and an Area Under the Curve of 0.94, meeting or exceeding the accuracy of other techniques used to predict replicability. The repliCATS process provides other benefits. It is highly scalable, able to be deployed for both rapid assessment of small numbers of claims, and assessment of high volumes of claims over an extended period through an online elicitation platform, having been used to assess 3000 research claims over an 18 month period. It is available to be implemented in a range of ways and we describe one such implementation. An important advantage of the repliCATS process is that it collects qualitative data that has the potential to provide insight in understanding the limits of generalizability of scientific claims. The primary limitation of the repliCATS process is its reliance on human-derived predictions with consequent costs in terms of participant fatigue although careful design can minimise these costs. The repliCATS process has potential applications in alternative peer review and in the allocation of effort for replication studies.

This paper explores judgements about the replicability of social and behavioural sciences research, and what drives those judgements. Using a mixed methods approach, it draws on qualitative and quantitative data elicited using a structured iterative approach for eliciting judgements from groups, called the IDEA protocol (‘Investigate’, ‘Discuss’, ‘Estimate’ and ‘Aggregate’). Five groups of five people separately assessed the replicability of 25 ‘known-outcome’ claims. That is, social and behavioural science claims that have already been subject to at least one replication study. Specifically, participants assessed the probability that each of the 25 research claims will replicate (i.e. a replication study would find a statistically significant result in the same direction as the original study). In addition to their quantitative judgements, participants also outlined the reasoning behind their judgements. To start, we quantitatively analysed some possible correlates of predictive accuracy, such as self-rated understanding and expertise in assessing each claim, and updating of judgements after feedback and discussion. Then we qualitatively analysed the reasoning data (i.e., the comments and justifications people provided for their judgements) to explore the cues and heuristics used, and features of group discussion that accompanied more and less accurate judgements.

Structured protocols offer a transparent and systematic way to elicit and combine/aggregate, probabilistic predictions from multiple experts. These judgements can be aggregated behaviourally or mathematically to derive a final group prediction. Mathematical rules (e.g., weighted linear combinations of judgments) provide an objective approach to aggregation. The quality of this aggregation can be defined in terms of accuracy, calibration and informativeness. These measures can be used to compare different aggregation approaches and help decide on which aggregation produces the “best” final prediction. When experts’ performance can be scored on similar questions ahead of time, these scores can be translated into performance-based weights, and a performance-based weighted aggregation can then be used. When this is not possible though, several other aggregation methods, informed by measurable proxies for good performance, can be formulated and compared. Here, we develop a suite of aggregation methods, informed by previous experience and the available literature. We differentially weight our experts’ estimates by measures of reasoning, engagement, openness to changing their mind, informativeness, prior knowledge, and extremity, asymmetry or granularity of estimates. Next, we investigate the relative performance of these aggregation methods using three datasets. The main goal of this research is to explore how measures of knowledge and behaviour of individuals can be leveraged to produce a better performing combined group judgment. Although the accuracy, calibration, and informativeness of the majority of methods are very similar, a couple of the aggregation methods consistently distinguish themselves as among the best or worst. Moreover, the majority of methods outperform the usual benchmarks provided by the simple average or the median of estimates.

Replication is a hallmark of scientific research. As replications of individual studies are resource intensive, techniques for predicting the replicability are required. We introduce a new technique to evaluating replicability, the repliCATS (Collaborative Assessments for Trustworthy Science) process, a structured expert elicitation approach based on the IDEA protocol. The repliCATS process is delivered through an underpinning online platform and applied to the evaluation of research claims in social and behavioural sciences. This process can be deployed for both rapid assessment of small numbers of claims, and assessment of high volumes of claims over an extended period. Pilot data suggests that the accuracy of the repliCATS process meets or exceeds that of other techniques used to predict replicability. An important advantage of the repliCATS process is that it collects qualitative data that has the potential to assist with problems like understanding the limits of generalizability of scientific claims. The repliCATS process has potential applications in alternative peer review and in the allocation of effort for replication studies.