Domestic dogs are very different from their wolf ancestors in their bodies and their behaviour. They’re more docile for a start. But man’s best friend has also evolved a curious sensitivity to our communication signals – a mental ability that sets them apart from wolves and that parallels the behaviour of human infants. Dogs and infants are even prone to making the same mistakes of perception.
Like infants less than a year old, dogs fail at a seemingly easy exercise called the “object permanence task”. It goes like this: if you hide an object somewhere(say a ball under a cup) and let the baby retrieve it a few times, they will continue to search for it there even if you hide it somewhere else (say behind the sofa) and even if you do so in front of their eyes. Piaget, the legendary psychologist who discovered this behaviour, thought that it reflected a wildly different way of seeing the world.
More recently, Jozsef Topal suggested that it’s the influence of the adult experimenter that’s the key. By repeatedly pointing at the ball in the first hiding place, the adult enshrines a generalised rule in the infant’s mind. And infants, being programmed to learn from communicative signals, come to believe the adult’s instructions over the evidence of their own eyes (some people apparently never grow out of this, but I digress). Topal demonstrated this by showing that infants were much better at the task if the experimenters avoided social cues like calling the child’s name or eye contact.
And the same is true for domestic dogs. Topal tested a dozen adult dogs with a version of the hidden-object challenge, concealing toy behind one of two possible screens. If he called to the dogs by name, made eye contact and waved, the animals made the same errors that infants make on 75% of the trials. Without any of these signals, their scores improved and they only failed to realise the ball’s new location on 39% of the trials. Their error rate dropped even lower in completely non-social situations, where the ball was moved by pulling on a transparent string.
These results suggest that dogs and infant share a social mindset where certain cues prepare them to learn from humans. It’s not the case that the gestures and facial signs were just distracting for that would lead the animals or infants to search both hiding places equally – instead, they both preferred the one that the object was initially hidden behind.
Dogs, it seems, have a particular breed of social smarts even as inexperienced puppies and some scientists have suggested that these skills are adaptations that have developed over the last 10,000 years to allow dogs to better interact with their two-legged partners.
Learning a new language as an adult is no easy task but infants can readily learn two languages without obvious difficulties. Despite being faced with two different vocabularies and sets of grammar, babies pick up both languages at the same speeds as those who learn just one. Far from becoming confused, it seems that babies actually develop superior mental skills from being raised in a bilingual environment.
By testing 38 infants, each just seven months old, Agnes Melinda Kovacs and Jacques Mehler have found that those who are raised in bilingual households have better “executive functions“. This loose term includes a number of higher mental abilities that allow us to control more basic ones, like attention and motor skills, in order to achieve a goal. They help us to plan for the future, focus our attention, and block out instinctive behaviours that would get in the way. Think of them as a form of mental control.
The role of these abilities in learning multiple languages is obvious – they allow us to focus on one language, while preventing the other from interfering. Indeed, children and adults who learn to use two languages tend to develop better executive functions. Now, Kovacs and Mehler have found that even from a very young age, before they can actually speak, children develop stronger executive functions if they grow up to the sound of two mother tongues. They show a degree of mental control that most people their age would struggle to match.
Kovacs and Mehler worked with 14 babies who heard two languages from birth, and 14 who had experienced just one. The babies saw a computer screen with two white squares and heard a short, made-up word. After that, a puppet appeared in one of the squares. There were nine words in total, and each time the puppet appeared in the same place. As the test went on, all the babies started focusing on the correct square more frequently, showing that they had learned to anticipate the puppet’s appearance. That’s a simple task that doesn’t require much in the way of executive function.
The next nine trials used a different puppet that appeared in the other square. The infants’ job was to learn that the link between word and puppet had changed, but only the bilingual ones were good at this. Unlike their monolingual peers, they learned to switch their attention to the other square. To Kovacs and Mehler, this is a sign of superior mental control – they had to override what they had previously learned in order to pick up something new. The monolingual infants, however, behaved as babies their age usually do – they stick with responses that had previously paid off, even if situations change.
Babies can say volume without saying a single word. They can wave good-bye, point at things to indicate an interest or shake their heads to mean “No”. These gestures may be very simple, but they are a sign of things to come. Year-old toddlers who use more gestures tend to have more expansive vocabularies several years later. And this link between early gesturing and future linguistic ability may partially explain by children from poorer families tend to have smaller vocabularies than those from richer ones.
Vocabulary size tallies strongly with a child’s academic success, so it’s striking that the lexical gap between rich and poor appears when children are still toddlers and can continue throughout their school life. What is it about a family’s socioeconomic status that so strongly affects their child’s linguistic fate at such an early age?
Obviously, spoken words are a factor. Affluent parents tend to spend more time talking to their kids and use more complicated sentences with a wider range of words. But Meredith Rowe and Susan Goldin-Meadow from the University of Chicago found that actions count too.
Children gesture before they learn to speak and previous studies have shown that even among children with similar spoken skills, those who gesture more frequently during early life tend to know more words later on. Rowe and Goldin-Meadow have shown that differences in gesturing can partly explain the social gradient in vocabulary size.