Piglets Learn to Use Combined Human-Given Visual and Auditory Signals to Find a Hidden Reward in an Object Choice Task

Abstract

Although animals rarely use only one sense to communicate, few studies have investigated the use of combinations of different signals between animals and humans. This study assessed for the first time the spontaneous reactions of piglets to human pointing gestures and voice in an object-choice task with a reward. Piglets (Sus scrofa domestica) mainly use auditory signals–individually or in combination with other signals—to communicate with their conspecifics. Their wide hearing range (42 Hz to 40.5 kHz) fits the range of human vocalisations (40 Hz to 1.5 kHz), which may induce sensitivity to the human voice. However, only their ability to use visual signals from humans, especially pointing gestures, has been assessed to date. The current study investigated the effects of signal type (visual, auditory and combined visual and auditory) and piglet experience on the piglets’ ability to locate a hidden food reward over successive tests. Piglets did not find the hidden reward at first presentation, regardless of the signal type given. However, they subsequently learned to use a combination of auditory and visual signals (human voice and static or dynamic pointing gestures) to successfully locate the reward in later tests. This learning process may result either from repeated presentations of the combination of static gestures and auditory signals over successive tests, or from transitioning from static to dynamic pointing gestures, again over successive tests. Furthermore, piglets increased their chance of locating the reward either if they did not go straight to a bowl after entering the test area or if they stared at the experimenter before visiting it. Piglets were not able to use the voice direction alone, indicating that a combination of signals (pointing and voice direction) is necessary. Improving our communication with animals requires adapting to their individual sensitivity to human-given signals.

Goats Follow Human Pointing Gestures in an Object Choice Task

“…The first two gestures included a decreased distance between the index finger of the experimenter and the rewarded bucket, compared to the asymmetric condition. This indicates that stimulus/local enhancement and/or positive reinforcement to approach a human hand (or the human itself) might best explain the good performance in the proximal and crossed condition (Krueger et al, 2011;Bensoussan et al, 2016). However, the low direct approaches to the experimenter's finger indicate that goats did not show increased interest to physically interact with the experimenter per se.…”

Comparing interspecific socio-communicative skills of socialized juvenile dogs and miniature pigs

“…The observation that both species were performing a considerable amount of explorative behaviour in the Control condition—besides the explicitly coded ones—gives further support to the above argument. All this is important, since multiple works with farm pigs pointed out the appearance of fearful or aggressive behaviours at the onset of the experimental procedures that made it necessary to include several occasions of familiarization procedures before the start of the data collection (e.g., Bensoussan et al 2016; Nawroth et al 2013, 2014). Therefore, working with family pigs instead of farm animals supports the comparability of the two species’ behaviour in the present experimental procedures.…”

“…The owner (O) sat on a chair—at 2 m distance from the experimenter (E)—and remained passive throughout the experiment. We followed the method by Bensoussan et al (2016), and we added a Control condition as well. The experiment consisted of two 120 s long sessions; the Control condition followed by the Food condition in fixed order after a short break, and both of them consisted of similar pre-test and test phases.…”

“…In this experiment, we aimed to investigate and compare the two species’ spontaneous behaviours exhibited towards an unfamiliar experimenter in two unrestricted consecutive short sessions, without the presence of food and when previously provided food reward was withheld. We partly based our method on the work done by Bensoussan et al (2016).…”

“…Nawroth et al (2013) have shown that young group-living farm pigs seem to react somewhat differentially to the different attentive states of a human (Nawroth et al 2013). In spite of the fact that in one study farm pigs did not prove to be sensitive to human-given referential signals (i.e., pointing gesture) (Albiach-Serrano et al 2012), with notable amount of previous training sessions farm-housed piglets were able to learn to use both proximal and distal pointing gestures to find hidden food reward (Nawroth et al 2014, 2016; Bensoussan et al 2016).…”