Functional lateralization in domestic pigs (Sus scrofa): Interactions with emotions and personality
Sensory and Behavioural Biology
Final Report Abstract
In the project “Functional lateralization in domestic pigs (Sus scrota): Interactions with emotions and personality” we aimed to create a first overview of functional lateralization in domestic pigs and to determine whether knowledge of functional lateralization in domestic pigs may be a useful tool for pig welfare research. To achieve this we had planned 2 work packages, with each 3 studies. In the first work package we studied lateralized processing of emotions in the visual and olfactory modality (WP1.2 and 1.2) and interactions between motor lateralization and personality indices (WP 1.3). In the second work package we studied lateralized auditory processing of emotions in more detail, focussing on non-biological conditioned stimuli (WP 2.1), on pig vocalizations (WP2.2) and on effects of individual tail biases (WP2.3). The experiments were performed with a few major and several minor adaptations from the proposal. Generally, we had to reduce the sample size in most experiments due to shortage of staff and subjects (all WP except WP1.3, which was performed first). To avoid loss in power, we converted most designs to a (partial) paired design, with each subject tested under different treatments. Pilot tests showed that conditioning trials had to be reduced to avoid habituation to the negative reinforcer (WP1.1, 1.2 and 2.2). With 3 studies completed (3 published and 1 prepared papers) and 3 still being analysed, our first findings show evidence of lateralized processing of emotional stimuli in the visual and auditory modality and of interactions between individual motor laterality patterns and indices of personality. In the visual modality we found that after positive conditioning to an object, covering the right eye (reducing transmission to the left hemisphere) caused longer latencies to touch this object and to vocalize after it was introduced, a shorter exploration of the arena and increased vagal activity compared to binocular viewing. This suggests an important role of the left hemisphere in the initial recognition of positive stimuli. In the auditory modality we found indications of lateralized processing in the initial perception (left head turn bias) and subsequent appraisal (subtle increases in arousal during playback to the left ear) of emotional relevant calls (produced during restraint). Conversely there were indications of lateralized processing only in the appraisal (increased attention during playback to the right ear) of communicative relevant calls (produced during isolation). We found that most of the pigs had a significant side bias for manipulating with their snout and curling their tail, indicating lateralization on the individual level. We also found a significant right bias at the population level for the tail curling direction. Using a cluster analysis with combined tail and snout laterality, we identified groups of individuals with different lateralization patterns across motor functions that potentially reflect the individuals’ hemispheric dominance. We found that the direction of the single motor biases showed significant associations with few personality traits. However, the combined laterality classification (based on the cluster analysis) showed more, and more robust, significant associations with different personality traits compared with the single motor biases. These results indicate that right-biased (left hemisphere dominant) pigs were bolder (shorter latency to touch a novel object) and more explorative (more interactions with a novel object) in a context of novelty and more sociable (more vocalizations in isolation) than left-biased pigs. Together our first findings show that pigs are lateralized in the processing of emotional stimuli and in different motor functions. Evidence of lateralization was found across different functional modalities (visual, auditory and motor) and across different emotional stimuli (biological and conditioned). Together the findings suggest that the left hemisphere is important for the processing of positive emotions, communication and the expression more bold, explorative and social behaviour, while the right hemisphere is more important for the processing of intense (negative) emotions and the expression of less bold, explorative and social behaviour. The findings show that knowledge of lateralized processing in pigs may indeed provide new insight in pig emotions and personality and therefore may be a useful addition to welfare research. These first findings already provide the basis for further investigations into the role of lateralization in the welfare consequences of farm management and the inclusion of indices of lateralized behaviour in non-invasive assessments of animal welfare.
Publications
- (2019) Visual laterality in pigs: monocular viewing influences emotional reactions in pigs. Animal Behaviour 154 183–192
Goursot, Charlotte; Düpjan, Sandra; Tuchscherer, Armin; Puppe, Birger; Leliveld, Lisette M.C.
(See online at https://doi.org/10.1016/j.anbehav.2019.06.021) - Behavioural lateralisation in domestic pigs (Sus scrota) - variations between motor functions and individuals. Laterality 2017, 23:5, 576-598
Goursot, C; Düpjan, S; Tuchscherer, A; Puppe, B; Leliveld, LMC
(See online at https://doi.org/10.1080/1357650X.2017.1410555) - Emotionale Valenz und Lateralisation beim Schwein. In: Nutztierhaltung im Fokus: Emotionen und Stimmung bei Nutztieren, published by the Internationale Gesellschaft für Nutztierhaltung (IGN), 2017, 14-17
Leliveld, LMC; Goursot, C; Düpjan, S; Puppe, B
- Assessing animal individuality: links between personality and laterality in pigs (Sus scrota). Current Zoology 2018, 1-11
Goursot, C; Düpjan, S; Kanitz, E; Tuchscherer, A; Puppe, B; Leliveld, LMC
(See online at https://doi.org/10.1093/cz/zoy071) - Visuelle Lateralisation und affektive Reaktionen beim Hausschwein. KTBL-Schrift 514:273-275, 2018
Goursot, C; Düpjan, S; Tuchscherer, A; Puppe, B; Leliveld, LMC
