Can animals guide their development?

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Long before children speak, they worry about the world

by Sabina Pauen

At just under one year old, babies understand the first words for objects. They show that they can categorize their early experiences. But how does one determine what belongs in a conceptual category and what does not? How is pre-linguistic knowledge about objects built up? How do babies use this knowledge to interpret their environment and how do they then learn to link preverbal categories with linguistic terms? Cognitive infant research provides revealing answers to these questions.


 

As long as a child cannot speak, it cannot really think either. This notion dominated developmental psychology until around 20 years ago. But our idea of ​​the relationship between language and thought has changed a lot in the meantime. Today we know that there is also pre-verbal thinking and that this pre-verbal thinking creates the prerequisite for the development of meaningful verbal communication.

It is easy to see why this is so: a child who we say not only makes any sounds but can also name things in a meaningful way always uses a certain word in similar contexts. For example, it means the same kind of thing over and over again. A word like "woof-woof" can be used to denote neighbors' poodles or poodles as a whole. Perhaps the child also means dogs in general or would even call a butterfly "woof-woof". The key is that the term is not used accidentally, but rather serves as a designation for a category of objects that already exists in his head and is the result of a process of spiritual search for order in the world.

As this example shows, words can refer to categories of different widths. Infant cognitive research has taken up this aspect and asked itself whether babies first form very narrow object classes or whether they begin their thinking with rather rough classifications. So the question is whether we should think of preverbal thought development as a process of increasing abstraction or differentiation.

Adults classify objects on different hierarchical levels in parallel. This is how one differentiates the so-called basic level, on which most of the terms are located. Objects in the same basic category are similar to one another in many dimensions and at the same time can be easily distinguished from objects in other categories. Mainly for this reason, the most commonly used object words in our language refer to the basic level. Dog, bird, fish are all examples of basic categories. If even finer differentiations are found within a basic category, we are talking about the subordinate level. Poodles, Dachshunds, Terriers are examples of subcategories within the basic class of dogs. Here the similarity between the items of a category is particularly great, but also the similarity between the different categories.

If you go further up in the hierarchy system, all of the basic categories mentioned so far can be summarized under the heading of animals. Such superordinate categories are naturally very heterogeneous - their members show many differences from one another. The more abstract the categories, the less the similarity between items of the same category, but also the similarity between the categories.

The question of what kinds of object categories babies form first is difficult to explore. Babies cannot express themselves verbally. And they can't sort either yet. Still, there is a way to examine these early accomplishments. The so-called “habituation-dishabigation paradigm” is based on the tendency of humans to be less interested in things that are familiar than in things that seem new to one.

A baby's interest can be determined, among other things, by how long it looks at an object (gaze time) or explores with hands and eyes (examination time). If you show babies the same object several times in a row, they will eventually become bored. Only when a new stimulus is presented does an orientation reaction take place again and interest rises again.

The situation is similar if you show different copies of the same category several times in a row (for example lots of pictures of cars) and at the end a copy from a different category (e.g. a picture of a truck). However, this only applies if the child can already distinguish between the two categories. Otherwise there will be no orientation reaction at the end. It is precisely this fact that infant research makes use of.

If you put children between the ages of seven and twelve months in a high chair and present them one after the other with different specimens of the same category in the form of three-dimensional miniature models of real objects, the child will show less interest in the new toys with each round and the duration of the examination will decrease . As could be shown, the observer agreement for such behavior measurements is very high. Using physiological measures such as heartbeat measurement, we were also able to prove that examination actually represents a phase of deepened intellectual preoccupation and thus an objectifiable measure of behavior.

If the same children who were initially used to a category are presented with a new copy of the same species and a new copy of the contrasted category during the test phase, the object of the new category will be examined for a comparatively longer time if the child distinguishes between the presented categories.

 
Lino is only seven months old, but already an experienced participant in the study. The employees of the Psychological Institute at Heidelberg University present Lino with various toys and derive his brain waves to find out what is going on in his head. Lino cannot speak yet, nevertheless he perceives his surroundings in a differentiated way and classifies things that he encounters into categories. This pre-linguistic thinking is the prerequisite for the development of meaningful verbal communication.

Photo: Hentschel

As a large number of studies that have now been carried out in different laboratories have documented, there is a general development trend in children in the first year of life in the sense of a global-to-basic-level shift: First a rough distinction is made between living beings and inanimate objects then finer distinctions are learned.

This observation was initially quite unexpected because it was thought that it should actually be easier for children to group together objects that look particularly similar (e.g. dogs or birds) than objects that have comparatively few external similarities (such as fish, birds, turtles) , Zebra, ladybug). Why the opposite is the case is still openly discussed today.

Today there are very different ideas about what babies are attached to, what belongs in a category and what does not. While one group of scientists asserted that even the early distinctions could only be traced back to an analysis of the characteristics of the external appearance of test stimuli, another group assumes that the behavior of objects is more important for concept formation than their appearance. In this case, the categorical differentiations observed in the laboratory would not only be due to on-line processes of visual comparisons, but the presented toy models would activate already existing category knowledge.

The data available to date do not allow a clear decision as to which assumption applies. On the one hand, it was possible to document that even very small babies (two to four months) who barely have enough previous experience can use image information to categorize objects on different hierarchical levels. Our own studies, which we are currently conducting in Heidelberg, also seem to show that the baby's brain systematically exhibits different arousal patterns in response to images of animals and artifacts. Such observations corroborate the importance of static features of external appearance for preverbal object categorization.

But at the same time we also have evidence that these are not the only relevant criteria. With eleven-month-old children, for example, we were able to show that their performance in a task with the global contrast between animals and furniture was almost identical once the test stimuli were designed in such a way that they showed more external similarities between the categories than within the categories and a other times the other way round. The only decisive factor for the children was whether the toy models clearly represented the same animals and furniture in both conditions. This finding is difficult to reconcile with the idea that the children orient themselves exclusively by the appearance of the test stimuli and have formed a new category during the test.

The results of another experiment also do not fit this assumption: children who have not had particularly intensive previous experience with cats and / or dogs cannot distinguish between the two basic categories at eleven months, while children with a cat or a dog in their household were very well able to make this categorical distinction. Both observations therefore suggest that prior knowledge is activated in the experiment. What prior knowledge this is, however, remains open. It could just as well be prior knowledge of the appearance of objects as prior knowledge of the behavior of objects. The question of what kind of babies makes the living being a living being remains open.

Some scholars attach great importance to facial features and legs in this context. They assume that we humans are born with an innate interest in faces and possibly other body features as well. As a result, an automatic sorting process could ensure that animals and humans are perceived differently from inanimate objects from the outset.

Various studies support this thesis by documenting that faces are actually of particular interest to newborns and that they can already use relevant information to categorize images of objects at two to four months old. At the same time, however, it is also clear that faces and body features cannot represent the only criteria for differentiating between object types. Otherwise it would be difficult to explain why the furniture and animals presented to the children, all of which have legs and face-like markings and therefore do not differ in this dimension, are nevertheless categorically differentiated from babies.

It is even more difficult to explain why babies separate people from animals at the age of seven months, even though both types of living being have identical faces and legs. By the way, they can do this regardless of whether they are provided with only head or body information in isolation. Such characteristics are apparently important in any case to distinguish individual species within the domain of living beings, but they are not the only decisive factor in the fact that babies distinguish between living beings and inanimate objects very early on. What is it then?

A very important criterion is exercise behavior. Babies are interested in everything that moves from birth, and very early on they manage to distinguish between things that can move on their own and things that only change their position under the influence of an external force. To do this, they don't even have to be able to see clearly. This criterion allows a clear separation of humans and animals on the one hand and plants or inanimate things on the other. In fact, plants are only added to living beings in primary school age. Before that, only humans and animals were considered alive.

As the latest infant studies document, the movement criterion is already used by seven-month-old babies for differentiation. In addition to movement behavior, children also seem to be particularly sensitive to the purposefulness of movement and the ability to communicate. Living beings are things that move on their own, act purposefully and with which one can enter into social exchange. This is how they distinguish themselves from inanimate objects.

It probably makes little sense to want to decide what is more important or comes first: the analysis of features of external appearance or the analysis of behavioral features. After all, both also refer to each other. Those who are particularly interested in faces will quickly notice that in most cases one can interact socially with things that have a face. Conversely, someone who is particularly interested in social interactions will quickly notice that the things that can be done with typically have faces. The same applies to the interest in movement and legs or other body parts that are related to movement behavior. Because it is the case in nature that these characteristics are not independent of one another, babies learn very early to relate them to one another and to use this world knowledge for their category formation.

In real life, category affiliation is more likely to be identified the more cues are available. These can be features of external appearance as well as features of behavior. If both come together, identification is particularly easy and can help to interpret new situations.

Our own experiments demonstrate this vividly: In the first scene, you show seven-month-old babies an unknown animal with facial features, fur and feather legs that make it easily identifiable as an animal from the outside, as well as a colorful plastic ball with dots, with both objects stationary lie in different corners of a small stage, then the babies look at these two objects only briefly and seem to prefer neither of them particularly.

If you show them in a second scene how the two objects roll around each other in constant contact on a small stage, the babies follow what is happening with great attention and hardly avert their eyes. If you then present the first scene again (animal and ball lie motionless next to each other), you now look at the animal with much more attention than before, while the viewing times for the ball decrease.

This longer look tells us that the babies expect the animal, but not the ball, to start moving again. This effect collapses when (a) the animal's facial features are removed, (b) the fur body is replaced by an artificial spiral, or (c) both objects are moved externally by one hand. In other words: The combination of certain characteristics of external appearance with characteristics of behavior is particularly suitable for activating previous knowledge in the child and using this knowledge to interpret a given situation and, on this basis, to anticipate what will happen next.

In the specific case, the child drew the conclusion from the constellation of the perceived stimuli that it must have been the animal that caused the movement in the second scene (if this could be identified as an animal and the movement was self-initiated) and the specific expectation deduced that the animal, and not the ball, is likely to move next. This last point is crucial!

We always have to make it clear to ourselves that everything we call human thinking, including categorical thinking, does not ultimately take place in a vacuum, but rather serves a specific purpose. The purpose of creating categories is to order experiences in order to enable economic recourse to these experiences, in order to be able to classify new situations and to interpret given constellations in such a way that an appropriate reaction is possible. The prediction of behavior plays a central role in this. It is therefore also plausible to assume that the analysis of the behavior of objects should already be decisive in the pre-linguistic formation of terms.

So let's summarize: Long before children begin to communicate verbally, they perceive their environment in a differentiated manner and think about the objects they encounter. They organize their experiences with the material world by first making a rough division into living beings (humans, animals) and inanimate objects.

This classification is based on both external appearance and behavior. Both are coupled early in the memory. In this way, it is possible to assign objects to categories on the basis of static and / or dynamic features and, on the basis of this identification process, to interpret new situations, make predictions and react appropriately.

On the basis of these insights, we are now specifically investigating how children's world knowledge differentiates itself in the course of the first year of life, how babies use this knowledge to interpret their environment and how they then learn to link preverbal categories with linguistic terms.In contrast to previous research, brain physiological measures are now increasingly included.

 

Prof. Dr. Sabina Pauen has headed the Department of Developmental Psychology and Biological Psychology at the Psychological Institute of Heidelberg University since 2002. She previously worked at the Universities of Gießen, Tübingen and Magdeburg and spent a year as a research fellow at Cornell University (Ithaca). For more than 15 years she has been concerned with cognitive development in early childhood. In 1999 she received the Charlotte and Karl Bühler Prize from the German Psychological Society for her research.
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