On the intra-laboratory replicability of results in animal cognition research, obtained in animals that were not exposed to, or unaffected by, experimental manipulations - Exemplified by spatial learning in pigs (Sus Scrofa Domesticus) across 12 holeboard studies

Abstract

The replicability of experimental results is considered a cornerstone of empirical research. However, the reproducibility of results from groups that have not undergone experimental manipulation -- the standard against which comparisons in an experiment are made -- has been almost entirely neglected in animal research. Our aim is to address this gap by exemplarily determining within-laboratory replicability using research in pigs, an increasingly popular large animal model species. Drawing on data from twelve independent porcine holeboard studies conducted in our laboratory, we examine the replicability of groups that were not subjected to experimental manipulation (typically the control group), eventually including groups on which the experimental treatments had no effect. These analyses were also performed on all eight studies involving the Terra x Finnish Landrace x Duroc pig breed, with all other breeds excluded to increase genetic uniformity. The holeboard is a complex spatial discrimination task in which an animal must learn to find food at four of sixteen possible locations (holes) arranged in a 4 x 4 matrix. The main variables measured are spatial working memory (WM), reference memory (RM) and the inter-visit interval (IVI), which serves as an index of motivation. All studies showed predominantly linear improvements in WM and learning rates across successive trial blocks. IVI showed greater variation across trialblocks, but this did not affect WM and RM learning, which are robust and replicable indices of spatial learning in pigs. Assessing replicability provides relevant information, such as whether behavioural and physiological traits in a model species are stably expressed and robust across studies. Including replicability research and publishing its results can stimulate the development and use of more replicable methods and workflows, thereby increasing scientific rigour. Provided the data are available and accessible, the next step should be to expand replicability studies to include those conducted in different laboratories.