Investigating food preference in zoo-housed meerkats.

Understanding food preference among animals in human care can support improvements to welfare through training and day-to-day care (e.g., diet management). Little has been published about food preference in zoo-housed meerkats. Assessing meerkat food preference would be useful, not only for the welfare of that species, but also for developing approaches to assessing food preference in other group-housed, social species. The specific aim of this study was to quantify food preference within the meerkat mob at Wellington Zoo. We developed a simple, cost-effective method for characterizing the food preference hierarchy in meerkats by presenting pairs of foods to the mob as a group. We observed stable preference with the hierarchy for pups closely resembling that for adults. This study demonstrated that it is possible to assess food preference and identify a food preference hierarchy for a group of animals from a social species where it was neither practical nor appropriate to assess individuals' preferences separately.

Visibly constraining an agent modulates observers' automatic false-belief tracking.

Our motor system can generate representations which carry information about the goals of another agent's actions. However, it is not known whether motor representations play a deeper role in social understanding, and, in particular, whether they enable tracking others' beliefs. Here we show that, for adult observers, reliably manifesting an ability to track another's false belief critically depends on representing the agent's potential actions motorically. One signature of motor representations is that they can be disrupted by constraints on an observed agent's action capacities. We therefore used a 'mummification' technique to manipulate whether the agent in a visual ball-detection task was free to act or whether he was visibly constrained from acting. Adults' reaction times reliably reflected the agent's beliefs only when the agent was free to act on the ball and not when the agent was visibly constrained from acting. Furthermore, it was the agent's constrained action capabilities, rather than any perceptual novelty, that determined whether adult observers' reaction times reliably reflected the agent's beliefs. These findings signal that our motor system may underpin more of social cognition than previously imagined, and, in particular, that motor representations may underpin automatic false-belief tracking.

Level 2 perspective-taking distinguishes automatic and non-automatic belief-tracking.

Little is known about whether human beings' automatic mindreading is computationally restricted to processing a limited kind of content, and what exactly the nature of that signature limit might be. We developed a novel object-detection paradigm to test adults' automatic processing in a Level 1 perspective-taking (L1PT) context (where an agent's belief, but not his visuospatial perspective, is relevantly different) and in a Level 2 perspective-taking (L2PT) context (where both the agent's belief and visuospatial perspective are relevantly different). Experiment 1 uncovered that adults' reaction times in the L1PT task were helpfully speeded by a bystander's irrelevant belief when tracking two homogenous objects but not in the L2PT task when tracking a single heterogeneous object. The limitation is especially striking given that the heterogeneous nature of the single object was fully revealed to participants as well as the bystander. The results were replicated in two further experiments, which confirmed that the selective modulation of adults' reaction times was maintained when tracking the location of a single object (Experiment 2) and when attention checks were removed (Experiment 3). Our findings suggest that automatic mindreading draws upon a distinctively minimalist model of the mental that underspecifies representation of differences in perspective relative to an agent's position in space.

Fate of Listeria monocytogenes on Fresh Apples under Different Storage Temperatures.

Fresh apples are typically stored for up to 1 year commercially; different apple varieties require different storage temperatures to maintain their quality characteristics. There is sparse information available about Listeria monocytogenes survival on fresh apples under various storage temperatures. The objective of this study was to comprehensively evaluate the effect of storage temperature on apple fruit decay and L. monocytogenes survival. Unwaxed apple fruits of selected varieties (Fuji and Granny Smith) were dip inoculated in a three-strain L. monocytogenes cocktail to establish ∼3.5 and 6.0 Log10 CFU/apple. Twenty-four hours post-inoculation, apples were subjected to 1, 4, 10, or 22°C storage for up to 3 months. Apples under the different storage treatments were sampled at 1-, 4-, 7- and 14-day for short-term storage under all four tested temperatures, and 2-, 4-, 8-, and 12-week for long-term storage at 1, 4, and 10°C. A set of uninoculated and unwaxed apples were simultaneously subjected to the previously mentioned storage temperatures and sampled biweekly for their total bacterial count (TPC) and yeasts/molds (Y/M) count. During the 2-week short-term storage, L. monocytogenes population on organic Granny Smith apples stored at 1, 4, or 10°C was reduced by 0.2-0.3 Log. When apples were stored at 22°C, there was a 0.5-1.2 Log10 CFU/apple reduction 14-day post storage dependent on the initial inoculation level. During the 12-week cold storage under 1, 4, and 10°C, L. monocytogenes count on organic Granny Smith apples decreased by 0.5-1.5 Log10 CFU/apple for both inoculation levels. L. monocytogenes had similar survival pattern on conventional Granny Smith and Fuji apples with 0.8-2.0 Log10 CFU/apple reduction over a 3-month cold storage period. Interestingly, both TPC and Y/M count were stable regardless of apple variety or cultivation practice during the 12-week storage at all tested temperatures. In summary, while L. monocytogenes did not proliferate on apple surfaces during 12 weeks of refrigerated storage, only a limited reduction of L. monocytogenes was observed in this study. Therefore, the apple industry cannot rely on cold storage alone to control this pathogen. Additional interventions are needed to eradicate Listeria on fresh apples during long-term cold storage.

Reaction time profiles of adults' action prediction reveal two mindreading systems.

Human beings are able to quickly step into others' shoes to predict peoples' actions. There is little consensus over how this cognitive feat might be accomplished. We tested the hypotheses that an efficient, but inflexible, mindreading system gives rise to appropriate reaction time facilitation in a standard unexpected transfer task, but not in a task involving an identity component. We created a new behavioural paradigm where adults had to quickly select whether an actor would reach, or not reach, for an object based on the actor's false belief about the object's location. By manipulating the type of object we compared participants' responding behaviour when they did and did not have to take the actor's perspective into account. While the overall accuracy reflected a high level of flexible belief reasoning across both tasks, the pattern of response times across conditions revealed a limit in the processing scope of an efficient mindreading system. Thus, we show, for the first time, that there are indeed different profiles of reaction times for object-location scenarios and for object-identity scenarios. The results elevate growing evidence that adult humans have not one, but two mindreading systems for dealing with mental states that underlie action.