Bearing fruit: Piloting a novel judgment bias task in an American black bear

Abstract

Judgment bias tasks can reveal changes in affect in animals as a function of environmental manipulations such as provision of enrichment. We assessed affect in an American black bear across seasonal changes in availability of a mulberry bush. We used a novel judgment bias task in which the background color of a touchscreen signaled whether the left or right positioned stimulus was correct. The bear learned the conditional rule in which the correct action for the white background (choose left) resulted in three pieces of food and the correct action for the black background (choose right) resulted in one piece of food. On probe trials involving intermediate gray backgrounds, left side responses indicated optimism and right side responses indicated pessimism. Tests took place at the beginning, middle, and end of mulberry season and again nearing the end of the summer and early fall before hibernation. The bear showed the most optimistic responses during the phase involving increased opportunities for foraging on mulberry. A follow‐up experiment confirmed that the bear preferred three food items over one food item, suggesting the quantity‐based discrimination was in fact salient to this bear. This is the first evidence for conditional discrimination learning in a black bear, validating the task to assess changes in affect.

A Food for All Seasons: Stability of Food Preferences in Gorillas across Testing Methods and Seasons

“…Our results add to the literature suggesting that touchscreen images are seen as representing real food items [10,20,21,[27][28][29][30]. Primates in previous studies demonstrated transfer of preferences from trained stimuli to novel images of the same food, indicating that they represented the images as depicting particular foods [19].…”

“…These findings suggest that presentation of food items using images presented on touchscreen computers may be a valid way to assess food preferences, at least in primates and other species with similar visual systems. Other work suggests that it is also a valid method for testing food preferences in bears [21,28,29]. We have gone beyond previous work to show that the method can be validated both through comparison to choices of actual food items and preferences for images of preferred food items when paired with randomly selected images of less preferred foods.…”

“…Previous studies had shown that animal subjects respond to photographs of food that correspond to preferences for actual food items either by selecting images of greater quantities of food items or images of more highly chosen foods when paired with images of smaller quantities of food items or less highly chosen foods. A black bear that demonstrated picture object correspondence [28] spontaneously preferred to select three pieces over one piece of almond depicted pictorially [29] although the gorillas tested in the current study did not show the same preference for images of three biscuits over one biscuit in a previously published study [30]. However, two sloth bears (Melursus ursinus) chose high-preference items in 80% of trials in which they were presented with a lower-preference food item and they transferred this preference to novel images of the foods [21].…”

What's not to like about Likert? Developing a nonverbal animal preference scale (NAPS)

“…It is possible that the nature of the task itself-requiring a conditional discrimination-rather than a failure of the representational nature of the categories of preferred and less preferred foods, led to the gorillas' difficulty. While assessing optimism and pessimism in the same gorillas using a novel judgment bias task that also required a conditional discrimination (i.e., if black background, choose right, if white background, choose left), the gorillas also struggled to learn the discrimination (McGuire & Vonk, 2018) although it was mastered by a black bear in fewer than 100 trials (Vonk et al, 2021). Furthermore, Bernstein-Kurtycz et al (n.d.) presented a version of the same task to two brown bears and one bear also learned the discrimination.…”

“…When the gorillas were trained to receive three versus one piece of a biscuit when selecting images that represented the same amounts of biscuit, they chose more randomly than when presented with a choice of three versus one actual pieces of biscuit (McGuire & Vonk, 2018). Once again, a black bear tested in a similar task showed better evidence of understanding that selecting images of a larger quantity of food led to receiving a larger quantity (Vonk et al, 2021). Coupled with other gorillas' poor discrimination of images of bananas versus actual bananas (Perron et al, 2008), it is possible that gorillas are not the ideal candidates for procedures that require them to use visual stimuli to represent real objects.…”