Animal Cognition - July 2018

'''Intuitive optics: What great apes infer from mirrors and shadows (Voelter & Call, 2018)'''

In a series of experiments, researchers asked what kind of information great apes can infer from mirrors and shadows in order to help discriminate appearance from reality. In the first experiment, all ape species were able to locate food using a mirror or a shadow. In a second experiment they compared the shadow condition to a control condition where the experimenter placed a black rubber object on the side where the food was slid, to mimic a shadow in a sense. This was to see if the apes would perform the same using perceptually similar cues for where the food was hidden. However, they performed at chance in this new ‘arbitrary’ (black rubber object) condition while maintaining above chance in the shadow condition. Since the reward was always where the shadow or rubber object was, this finding was a little surprising to me. Experiment 3 assessed whether apes could extract depth information from a mirror. Subjects were able to adjust their response and select the truly closer food item despite appearing farther in the reflection. Experiment 4 manipulated angles of the mirror and experiment 5 compared mirror-naïve chimpanzees to chimps that had scored above chance on Experiments 1, 3, and 4. Before each trial subjects were shown either two mirrors, where they could see their own reflections, or two pictures, one of which looked like the reflection of the food. The food was always hidden where they could see its reflection or where the picture of the reflection was. Overall, experienced chimps performed better than naïve chimps in both the mirror and picture demonstration conditions. Notably, they performed much better than mirror-naïve chimps on the first trial of mirror demonstration trials. There is a lot going on here, but I think I would have liked to see a condition where they had to discriminate between an image and a mirror’s reflection rather than just something against nothing – as most of these conditions did.

'''Spatial representation of magnitude in humans (Homo sapiens), western lowland gorillas (Gorilla gorilla gorilla), and American black bears (Ursus americanus'') (Johnson-Ulrich & Vonk, 2018). ' '

Here’s one for the SNARC people. Subjects had to respond to either a smaller or larger array of dots, and the arrays were either static or moving. All species showed some evidence of a SNARC effect when looking at accuracy or response time. However, for bears and gorillas, the evidence was pretty limited – some individuals only showed an effect for accuracy or for response time, and only for congruent trials. No SNARC in human subjects for reaction time, and only 2 SNARC effects based on accuracy. The effects were clearer once regression slopes were standardized, with nearly all groups showing an effect, but direction and strength of effect varied across subjects. The authors point out that a lack of explicit instructions may have contributed to this and suggest that his testing paradigm may not be the best for assessing the SNARC effect in comparative research. In other words, for a phenomenon assumed present in humans, only testing paradigms that produce robust results for humans should be used to assess the phenomenon in nonhuman species.

'''Neophobia does not account for '''motoric self-regulation performance as measured during the detour-reaching cylinder task (Stow, Vernouillet, & Kelley, 2018)'''

Two species of corvids were assessed for neophobic behaviors using novel environment and novel object exploration paradigms. Then, a detour-reaching cylinder task was used to examine motoric inhibitory control. The scores from the two measures of neophobia (novel environment and novel object) did not correlate with each other. These scores also did not explain individual differences in cylinder task performance (neither did species or sex or their interaction) – suggesting that neophobic responses do not relate to motoric self-regulation in these species. This study was partially based off one that did find performance in a detour task affected by novelty responses in domestic chicks (Regolin et al, 1994: Perceptual and motivational aspects of detour behavior in young chicks. Anim Behav 47, 123-31.)

'''Pigeons play the percentages: computation of probability in a bird (Roberts, MacDonald, & Ha Lo, 2018)

Another probability paper for you guys. Here researchers tested pigeons in an operant chamber with keys that reinforced at different probabilities. There was a preference for a key that reinforced 75% of the time over a key that reinforced 25% of the time, even when the keys yielded the same overall amount of reinforcers. In experiment 3, when both keys provided 50% reinforcement pigeons showed no preference, even though one key provided 3 times as many reinforcers. The authors conclude that the pigeons are basing their choices on the probabilities the keys will reinforce rather than on the total amount of reinforcers they are receiving. Their choices are a little unexpected (selecting the 75% key even more than would be expected if subjects were probability matching), but towards the end the authors break down the overall rate of reinforcement for each key across the 3 experiments, showing a faster overall rate for the 75% key in experiments 1 and 2 and equal rates of reinforcement for the keys in experiment 3. So maybe the pigeons are basing their selection on the rate of reinforcement? Curious to see what you guys think of this one!

'''Where’s the cookie? The ability of monkeys to track object transpositions (Majecka & Pietraszewski, 2018)

Object permanence in 10 species of monkeys (19 total individuals). Experimenters placed a reward under 1 of 2 cups that always started in the same positions, but then were moved around according to several variants. Monkeys did well, getting the most right when the cup movements were less complex. Comparing to similar studies, monkeys did better than dogs but worse than apes.

Other articles that might interest some:

'Young macaques (Macaca fascicularis'') preferentially bias attention towards closer, older, and better tool users (Tan, Hemelrijk, Malaivijitnond, & Gumert, 2018)

Young macaques interact with adults to obtain food, but watch tool users perhaps in order to learn and maximize feeding opportunities.

'''Spatio-temporal organization during group formation in rats (Weiss, Levi, Segev, Simbirsky, & Eilam, 2018)

'''Relative salience of syllable structure and syllable order in zebra finch song (Lawson, Fishbein, Prior, Ball, & Dooling, 2018)

Testing domain general learning in an Australian lizard (Qi, Noble, Fu, & Whiting, 2018)'''

Lizards that performed well on a spatial task performed the same as lizards that did not perform well on a spatial task in an instrumental and a discrimination task. Overall, the lizards did well on all tasks. Authors suggest focusing on individual differences may be a better way of classifying learning abilities than an overall domain general or domain specific.