Both empirical and theoretical studies show that an individual's spatial position within a group can impact the risk of being targeted by predators. Spatial positions can be quantified in numerous ways, but there are no direct comparisons of different spatial measures in predicting the risk of being targeted by real predators. Here, we assess these spatial measures in groups of stationary and moving virtual prey being attacked by three-spined sticklebacks ( Gasterosteus aculeatus ). In stationary groups, the limited domain of danger best predicted the likelihood of attack. In moving groups, the number of near neighbours was the best predictor but only over a limited range of distances within which other prey were counted. Otherwise, measures of proximity to the group's edge outperformed measures of local crowding in moving groups. There was no evidence that predators preferentially attacked the front or back of the moving groups. Domains of danger without any limit, as originally used in the selfish herd model, were also a poor predictor of risk. These findings reveal that the collective properties of prey can influence how spatial position affects predation risk, via effects on predators' targeting. Selection may therefore act differently on prey positioning behaviour depending on group movement.

The effects of scopolamine were evaluated in monkeys responding under operant procedures designed to evaluate drug effects on learning and memory. In one procedure, responding was maintained by food presentation under a multiple schedule. One component of the multiple schedule was a repeated-acquisition task in which the discriminative stimuli for left- and right-key responses changed each session (learning). In the other component, the discriminative stimuli for responses were the same each session (performance). In both components of the multiple schedule, scopolamine produced dose-related decreases in responding; there was little evidence of differential rate-decreasing effects between components. Percent errors in learning were increased in a dose-related manner, whereas percent errors in performance were generally unaffected except at high doses, which also produced substantial decreases in response rate. These results suggest that acquisition is more sensitive to the disruptive effects of scopolamine than is performance. The second procedure utilized repeated acquisition and delayed performance as a technique to study the effects of scopolamine on memory. In this procedure, each session was divided into three phases: acquisition, delay and performance. After a 24-h delay, scopolamine had little or no effect on retention, accuracy or rate of responding. In contrast, after a 60-min delay, scopolamine decreased retention in a dose-related manner. These data suggest that scopolamine produces a greater disruptive effect on short (60-min) versus long (24-h) delays.

How negative results are reported and interpreted following null hypothesis significance testing is often criticised. With small sample sizes and often low number of test trials, studies in animal cognition are prone to producing non-significant p-values, irrespective of whether this is a false negative or true negative result. Thus, we assessed how negative results are reported and interpreted across published articles in animal cognition and related fields. In this study, we manually extracted and classified how researchers report and interpret non-significant p-values, and examined the p-value distribution of these non-significant results. We found a large amount of heterogeneity in how researchers report non-significant p-values in the result sections of articles, and how they interpret them in the titles and abstracts. “No Effect” interpretations were common in the titles (84%), abstracts (64%), and results sections (41%) of papers, whereas “Non-Significant” interpretations were less common in the titles (0%) and abstracts (26%), but were present in the results (52%). Discussions of effect sizes were rare (<5% of articles). A p-value distribution analysis was consistent with research being performed with low power research to detect effect sizes of interest.

Paying attention to weight is important when deciding upon an object's efficacy or value in various contexts (e.g. tool use, foraging). Proprioceptive discrimination learning, with objects that differ only in weight, has so far been investigated almost exclusively in primate species. Here, we show that while Goffin's cockatoos learn faster when additional colour cues are used, they can also quickly learn to discriminate between objects on the basis of their weight alone. Ultimately, the birds learned to discriminate between visually identical objects on the basis of weight much faster than primates, although methodological differences between tasks should be considered.