The media’s interest in feats of animal cognition seemed insatiable during December as one comparative study after another made news around the world. The greatest excitement of all was triggered by researchers at the Primate Research Institute in Japan, who observed a chimpanzee outperforming humans on a visual working memory task. Other studies showed chimps are able to distract themselves from temptation, that monkeys use human-like anticipation when gripping objects, and that dogs can distinguish between visual categories.
All the attention lavished on these studies prompts the question of why people continue to be so enthralled by animal feats, and begs the question too of what theoretical importance the research has beyond being fun to marvel at.
Dr Daniel Weiss of Pennsylvania State University, lead author on the monkey study, told us there was nothing new about our fascination with animal abilities. ‘Throughout history, philosophers such as Aristotle and Descartes, as well many scientists, notably Darwin among many others, have obsessed over the nature of the differences between humans and nonhumans. Today we are in a unique position to advance the arguments with greater precision by making simultaneous advances in studying behaviour, neurobiology and genetics. I think a greater proportion of the population has come to terms with the fact that we share common ancestry with other primate species, but we have yet to nail down what it is that makes us uniquely human.’
Weiss also explained the theoretical importance of comparative research: ‘The enterprise of comparative research is meant to determine areas of continuity in both psychological and cognitive mechanisms, as well as discovering the areas in which species’ abilities diverge. When we find cognitive similarities across species the challenge is really to determine whether the underlying representations are similar.
‘When differences emerge, we have to be extremely cautious in interpreting the data in order to ensure that we have posed the question to each species in a way that allows the full extent of their abilities to be expressed. If you look at these recent findings through the lens of natural selection, it is not surprising that we find that for some tasks, humans "outperform" other species, but, as Matsuzawa’s work has demonstrated, in other domains other species "outperform" humans. Each species has evolved mechanisms that are meant to facilitate their survival under a particular set of environmental and social conditions. Some of these mechanisms may have a lengthy evolutionary history, others may be more recent adaptations.’
The findings in brief
When numerals on a computer screen were quickly replaced by blank squares, with the task to touch the squares in the correct numerical order [for videos see tinyurl.com/38766f], nine humans beat the older of two chimps for accuracy, and both she and they showed deteriorating accuracy as presentation time reduced. However, chimp Ayumu’s accuracy was better than the humans’, and his performance did not diminish with reduced presentation time. Researchers Sana Inoue and Tetsuro Matsuzawa said this was a sign of ‘eidetic imagery’ - ‘the capability to retain an accurate detailed image of a complex scene or pattern’ - also observed in many young children before declining with age [tinyurl.com/2unmww].
Meanwhile at the Language Research Centre at Georgia State University in Atlanta, researchers observed chimps deliberately distracting themselves from temptation [for video, see tinyurl.com/39ljst]. Four chimps were confronted by a jar that continued filling with sweets until they grabbed it. Theodore Evans and Michael Beran found that when toys were available, the chimps played with these and were able to resist grabbing the jar for longer than when there were no toys, so gaining more sweets. Yet if the sweet jar was visible but out of reach, the chimps didn’t play with the toys so much, showing that in the temptation condition, they really were using the toys to distract themselves [tinyurl.com/yug479].
Not to be left out, monkeys have also been seen showing off their skills. Daniel Weiss and colleagues at Pennsylvania State University found that cotton-top tamarins exhibit the same kind of anticipatory reaching behaviour as humans [tinyurl.com/2wp5lo]. For example, when reaching for an inverted glass containing a marshmallow, the tamarins grasped the glass with an unusual thumb-down grip, in anticipation of turning it the right way around. Tamarins do not use tools in the wild, so the study showed anticipatory motor planning is a necessary but not sufficient skill needed for tool use.
Finally, a study by Friederike Range and colleagues at the University of Vienna showed that four dogs were able to distinguish between pictures of dogs and pictures of landscapes, and then correctly classify new dogs on old landscapes [tinyurl.com/2jxwuq]. The observation suggests dogs were able to follow categorisation rules in the way humans do, rather than just rote learning by category all the images they had been shown before.