Macphail's Null Hypothesis of Vertebrate Intelligence: Insights From Avian Cognition

A sequence bottleneck for animal intelligence and language?

We discuss recent findings suggesting that non-human animals lack memory for stimulus sequences, and therefore do not represent the order of stimuli faithfully. These observations have far-reaching consequences for animal cognition, neuroscience, and studies of the evolution of language and culture. This is because, if non-human animals do not remember or process information about order faithfully, then it is unlikely that non-human animals perform mental simulations, construct mental world models, have episodic memory, or transmit culture faithfully. If this suggested sequence bottleneck proves to be a prevalent characteristic of animal memory systems, as suggested by recent work, it would require a re-examination of some influential concepts and ideas.

Hominin cognition: The null hypothesis

The target article explores material culture datasets from three African forager groups. After demonstrating that these modern, contemporary human populations would leave scant evidence of symbolic behaviour or material complexity, it cautioned against using material culture as a barometer for human cognition in the deep past. Twenty-one commentaries broadly support or expand these conclusions. A minority offer targeted demurrals, highlighting (1) the soundness of reasoning from absence; and questioning (2) the "cognitively modern" null; (3) the role of hunter-gatherer ethnography; and (4) the pertinence of the inferential issues identified in the target article. In synthesising these discussions, this reply addresses all four points of demurral in turn, and concludes that there is much to be gained from shifting our null assumptions and reconsidering the probabilistic inferential links between past material culture and cognition.

Mechanical problem solving by plush-crested jays: are tools special after all?

Tool use is taxonomically associated with high behavioural flexibility and innovativeness, and its prevalence is greater in primates and some bird species. This association, however, is not known to be causally determinant of tool-related competence since flexibility and innovativeness are often observed in the absence of tool use and vice versa. For this reason, it is interesting to explore whether animals that can be loosely categorized as outstanding, or 'intelligent' physical problem solvers, are also remarkable using tools innovatively, rather than tool use presenting special constraints. We investigate this problem using plush-crested jays (Cyanocorax chrysops), a corvid new to cognitive research that shows highly flexible and inquisitive behaviour in the wild and has not been reported to use tools. We tested jays in two tasks of apparent similar manipulative complexity and incentive, one involving a tool (T) and the other not (NT). In the NT task birds had to open a box with a transparent lid blocked by a latch to get a reward, whereas in the T task, they had to use a rake to pull out the reward from the box. Eight out of nine subjects succeeded in the NT task, whereas none of them learned to solve the T task. This is consistent with tool use involving dedicated competencies, rather than just high problem-solving proficiency.

Longitudinal evidence for the emergence of multiple intelligences in assistance dog puppies

Cognitive test batteries suggest that adult dogs have different types of cognitive abilities that vary independently. In the current study, we tested puppies repeatedly over a crucial period of development to explore the timing and rate at which these different cognitive skills develop. Service dog puppies (n = 113), raised using two different socialization strategies, were either tested longitudinally (n =91) or at a single time point (n = 22). Subjects tested longitudinally participated in the battery every two weeks during and just beyond their final period of rapid brain growth (from approximately 8-20 weeks of age). Control puppies only participated in the test battery once, which allowed us to evaluate the impact of repeated testing. In support of the multiple intelligences hypothesis (MIH), cognitive skills emerged at different points across the testing period, not simultaneously. Maturational patterns also varied between cognitive skills, with puppies showing adult-like performance on some tasks only weeks after a skill emerged, while never achieving adult performance in others. Differences in rearing strategy did not lead to differences in developmental patterns while, in some cases, repeated testing did. Overall, our findings provide strong support for the MIH by demonstrating differentiated development across the cognitive abilities tested.

An Ecological and Neural Argument for Developing Pursuit-Based Cognitive Enrichment for Sea Lions in Human Care

While general enrichment strategies for captive animals attempt to elicit variable and species-typical behaviors, approaches to cognitive enrichment have been disappointingly one-size-fits-all. In this commentary, we address the potential benefit of tailoring cognitive enrichment to the "cognitive niche" of the species, with a particular focus on a reasonably well-studied marine carnivore, the sea lion. Sea lions likely share some cognitive evolutionary pressures with primates, including complex social behavior. Their foraging ecology, however, like that of many terrestrial carnivores, is based on the rapid and behaviorally flexible pursuit of avoidant prey. Unlike terrestrial carnivores, sea lions carry out this pursuit in a truly fluid three-dimensional field, computing and executing sensorimotor transformations from any solid angle to any other. The cognitive demands of flexible prey pursuit are unlikely to be fully elicited by typical stationary puzzle box style foraging enrichment devices or screen-based interactive games. With this species, we recommend exploring more water-based movement activities generally, and complex pursuit challenges specifically.

Dogs Mentally Represent Jealousy-Inducing Social Interactions

Jealousy may have evolved to protect valuable social bonds from interlopers, but some researchers have suggested that it is linked to self-awareness and theory of mind, leading to claims that it is unique to humans. We presented dogs (N = 18; 11 females; age: M = 4.6 years, SD = 1.9) with situations in which they could observe an out-of-sight social interaction between their owner and a fake dog or between their owner and a fleece cylinder. We found evidence for three signatures of jealous behavior in dogs: (a) Jealousy emerged only when the dog's owner interacted with a perceived social rival, (b) it occurred as a consequence of that interaction and not because of the mere presence of a conspecific, and (c) it emerged even for an out-of-sight interaction between the dog's owner and a social rival. These results support claims that dogs display jealous behavior, and they provide the first evidence that dogs can mentally represent jealousy-inducing social interactions.