Horses Solve Visible but Not Invisible Displacement Tasks in an Object Permanence Paradigm

Oriental pied hornbills (Anthracoceros albirostris) solve invisible displacement tasks in a test of Piagetian object permanence

Object permanence, the ability to mentally represent objects even when they are not directly accessible to the senses, is of vital importance for the survival of both human and non-human animals. The Oriental pied hornbill (Anthracoceros albirostris) is an Asian species of hornbill displaying remarkable adaptability in various environments, yet little is known about their cognitive abilities. Their breeding behaviour is unique, as the female hornbill seals herself inside a cavity before laying eggs and the male feeds her and their offspring without visual contact, strongly suggesting the presence of object permanence to some degree. In this study, six Oriental pied hornbills underwent testing for object permanence, including a series of seven standard Piagetian tasks involving visible and invisible displacements. The subjects consistently demonstrated spontaneous object permanence in all stages leading up to the invisible displacement stage. Half of the subjects achieved full stage 6 double invisible displacement Piagetian object permanence, while the other half reached stage 5 double visible displacement. Breeding behaviour and the duration of developmental stages are proposed as potential factors influencing object permanence ability in this species of hornbill.

Horses' (Equus caballus) Ability to Solve Visible but Not Invisible Displacement Tasks Is Associated With Frustration Behavior and Heart Rate

Many frameworks have assessed the ultimate and ontogenetic underpinnings in the development of object permanence, but less is known about whether individual characteristics, such as sex or training level, as well as proximate factors, such as arousal or emotional state, affect performance in these tasks. The current study investigated horses’ performance in visible and invisible displacement tasks and assessed whether specific ontogenetic, behavioral, and physiological factors were associated with performance. The study included 39 Icelandic horses aged 2–25 years, of varying training levels. The horses were exposed to three tasks: (a) a choice test (n = 37), (b) a visible displacement task (n = 35), and (c) an invisible displacement task (n = 31). 27 horses in the choice test, and 8 horses in the visible displacement task, performed significantly better than expected by chance, while none did so in the invisible displacement task. This was also reflected in their group performance, where horses performed above chance level in the choice task and the visible displacement task only. In the invisible displacement task, the group performed significantly worse than expected by chance indicating that horses persistently chose the side where they had last seen the target. None of the individual characteristics included in the study had an effect on performance. Unsuccessful horses had higher heart rate levels, and expressed more behavior indicative of frustration, likely because of their inability to solve the task. The increased frustration/arousal could lead to a negative feedback loop, which might hamper performance in subsequent trials. Care should thus be taken in future experimental designs to closely monitor the arousal level of the tested individuals in order to safeguard comparability.

Horses are sensitive to baby talk: pet-directed speech facilitates communication with humans in a pointing task and during grooming

Pet-directed speech (PDS) is a type of speech humans spontaneously use with their companion animals. It is very similar to speech commonly used when talking to babies. A survey on social media showed that 92.7% of the respondents used PDS with their horse, but only 44.4% thought that their horse was sensitive to it, and the others did not know or doubted its efficacy. We, therefore, decided to test the impact of PDS on two tasks. During a grooming task that consisted of the experimenter scratching the horse with their hand, the horses (n = 20) carried out significantly more mutual grooming gestures toward the experimenter, looked at the person more, and moved less when spoken to with PDS than with Adult-directed speech (ADS). During a pointing task in which the experimenter pointed at the location of a reward with their finger, horses who had been spoken to with PDS (n = 10) found the food significantly more often than chance, which was not the case when horses were spoken to with ADS (n = 10). These results thus indicate that horses, like certain non-human primates and dogs are sensitive to PDS. PDS could thus foster communication between people and horses during everyday interactions.