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When biologists and psychologists talk at cross-purposes
Press release in PDF-Version
Misunderstandings in communication happen every day—and this also
happens in the sciences. A new study explored the “theories behind the
theories” on “personality” and individual differences and unravelled
fundamental misunderstandings between biologists and psychologists. These
misunderstandings not only hamper collaborative research across
disciplines; but they can also mislead the development of theories. This
is an all-too-common story about how language can produce understanding
and misunderstanding. A story that can also be told in the sciences.
Almost 100 years ago, pioneers of psychology, such as Wolfgang Köhler,
Robert Yerkes and Donald Hebb and the physiologist and physician Ivan
Pavlov reported on pronounced individual differences in the behaviour of
animals, in particular, in great apes and dogs. But in those times, such
reports were regarded as unscientific and were dismissed as mere
anthropomorphism. The predominant idea was that only humans could develop
individuality. The idea that prevailed in biology until the 1990s was the
assumption that, in every animal species, there are optimal behavioural
patterns and that any deviations from these optima would be random and
thus unimportant. These beliefs were held despite the fact that Charles
Darwin had already recognised in 1859 that individual differences are a
vital precondition for evolution – but he had focussed on bodily
properties rather than on behavioural ones.
In the 1990s, both psychologists and biologists began to rethink their
assumptions. “Personality” differences were now increasingly being
explored from the viewpoint of evolution. Research on individual
behavioural differences in animals was becoming popular. It almost seemed
as though animal researchers could not wait to finally explore what had
for so long been considered non-existent and thus not worthy of
exploration. The number of animal studies increased rapidly, and with
them, the number of animal species being studied.
But the differences in the species being studied and
especially in the research methods that were being used in biology and
psychology led to tremendous difficulties and a bewildering diversity of
terms and concepts. Whereas a focus on individual differences and
individuality was still comparably new in biology, psychologists had
already been exploring these topics for more than 100 years. Francis
Galton, a relative of Charles Darwin, had already developed a
comprehensive body of psychological concepts and methods of analysis in
the 19th century.
It is important to distinguish between two central approaches. First, some
researchers study and categorise individual differences in a population;
this is the objective of research in Differential Psychology – the
psychology of individual differences. Individuals can differ from one
another, for example, in their degrees of anxiousness, gregariousness or
aggressive-ness. These differences between individuals describe the
particular population under study. Thus, the focus of differential
research is on the population.
But knowledge about individual differences does not reveal anything about
the particular combinations of features that may be specific to a
particular individual and that make this individual unique. This
individual-specific combination is called “personality”; it refers to the
person—the individual. For example, compared with other individuals of his
or her reference population, an individual may be very anxious, moderately
gregarious and hardly ever aggressive. Another individual, by contrast,
may be much less anxious, very gregarious but also far more aggressive
than others. Hence, in “personality” research, the central focus lies on
the single individual.
In everyday language, the term “personality” is used
almost exclusively with regard to single individuals. A comparison of
individuals with one another is commonly referred to as a consideration of
“personality” differences. But in research, a different use of language
was established additionally. This most likely happened because the
correct labelling of the two central areas of research resulted in rather
cumbersome terms. In the German-language area, for example, the entire
field today is called Differential and “Personality” Psychology. In the
English-language area, by contrast, “Personality” Psychology mostly refers
to both research on individual differences in populations and research on
single individuals.
All this could be considered an expression of scientific pedantry. But
psychologists’ imprecise and linguistically simplified use of terms caused
tremendous misunderstandings when biologists began to explore individual
differences and “personality” in animals in the 1990s. In a new study,
Jana Uher therefore explored the “theory behind the theories”—referred to
as meta-theory in science—and located exactly where misunderstandings have
occurred between researchers from different disciplines and what has
caused them.
In the last two decades, animal researchers have primarily focused on
individual differences that occur in particular populations of animals.
Bodily features, such as fur colour or body size, change rather slowly;
therefore, individual differences can be directly recognised. But
behaviour changes from moment to moment. These strong fluctuations make it
almost impossible to recognise individual differences directly. Jana Uher
showed that a behavioural pattern can be specific to an individual only if
it differs from those of other individuals and only if these differences
occur repeatedly in similar ways rather than just once. Thus, individual
differences in behaviour must be relatively stable for at least for some
period of time.
Animal owners are very familiar with this. A single
observation does not say much about how an individual typically
behaves—the individual might be scared right now or tired, hungry or ill.
When choosing a new pet, it is therefore advisable to observe one’s
potential new housemate on different occasions and to ask the breeder or
previous owner about its habitual behaviour. Here, also, the following is
very obvious: The fact that there are individual differences in the
behaviours of dogs, cats, horses and other individuals towards humans and
conspecifics does not say anything about what particular kind of
individual we have right in front of us. Rather, it is the combination of
typical behavioural tendencies that an individual shows in comparison with
other individuals—his or her “personality”.
The problem is that pronounced fluctuations in the behaviour of
individuals always lead to individual differences in behavioural data that
thus emerge by pure chance. Whether there are in fact “personality”
differences can be explored only by repeatedly studying the same
individuals: The individual differences must occur in similar ways again
after some time.
Now, here is a tricky point: How stable must individual differences be in
order to be interpreted as “personality” differences? Ultimately,
individuals also change over the course of their lives and as they develop
their “personality”. In psychology, differentiating “personality”
differences from mere random variation requires evidence for strong
stabilities across some number of weeks or months. By contrast, many
animal studies have reported about only weak or moderate stabilities even
across only short periods of time but they have interpreted these findings
as evidence of animal “personalities”. However, most animal studies
explore only individual differences. Stable yet individually distinct
combinations of behavioural patterns, to which the concept of
“personality” actually refers, have hardly ever been studied in animals.
“It is curious that in the past, individual differences
were dismissed as mere random variation in animal research. Today, animal
researchers interpret random variation as evolutionarily meaningful”, says
Jana Uher. She warns against premature conclusions. “Such dramatic changes
in the interpretation of research results are always in need of
explanation. They show that it is always the particular viewpoint of the
researchers that determines which particular phenomena are considered
worthy of an explanation and which ones are not.”
Jana Uher has also revealed fundamental differences in the
ways in which researchers analyse stability. Animal researchers often
report interrelations between different kinds of behaviours that show up
in similar ways again at later times in the animal population under study;
biologists call these behavioural syndromes. However, for identifying
“personality” differences, it is individual differences and their
stability over time that are essential. Certainly, when they are hungry,
all individuals of a given species show more feeding behaviour and take
more risks than when they are not hungry. This fact alone leads to
interrelations between feeding and risk behaviours that are stable over
time. But such findings do not show that in a given species there are, in
fact, some individuals that take more risks than others or that feed more
often than others.
So, what is it with the „personality“ of animals? Jana Uher assumes that
many differences between biological and psychological research on animals
derive from differences in the particular species being studied. Most
psychologists study only humans and the few psychological animal
researchers focus mostly on human’s closest living relatives, the nonhuman
primates. Biologists, by contrast, hardly ever study humans but they study
all animal species. She assumes that in primates and other mammals, there
are a number of pronounced individual differences and individual-specific
combinations of behavioural patterns. But such patterns may be much less
pronounced in fish and insects. Therefore, the findings—and thus also the
concepts—necessarily differ between the disciplines.
But Jana Uher emphasises: “It is only research that can
show which animal species show which particular kinds of stable individual
differences that can be interpreted as “personality” differences,
individual behavioural strategies or individual behavioural phenotypes and
that may be meaningful for the evolution of the species”. There are
methodologically sound studies from Australia showing that even octopuses
exhibit stable individual behavioural differences. Many dog studies have
shown what dog owners have already known for a long time: A dog’s
individual combination of behavioural patterns does not differ from day to
day and it is not merely random; rather, it characterises an individual
over at least some period of time. In her studies on great apes, Jana Uher
has shown how, on the one hand, stable individual behavioural differences
and, on the other hand, stable but individually different combinations of
behavioural patterns can be measured in “personality” profiles (see the
Science Blog “No one alike – ‘personality’ differences in the great
apes”).
The researcher offers a note of caution: “The methods required for
‘personality’ studies are a bit more tricky than those required in other
areas of research. This is still not well considered by many animal
researchers. Animal researchers should invest more in their research
methods. Otherwise, there is a risk that theories about the meaning and
evolution of ‘personality’ differences will be developed on the basis of
mere methodological errors.”
Scientific publication:
Uher, J. (2011a). Individual behavioral phenotypes: An integrative
meta-theoretical framework. Why 'behavioral syndromes' are not analogues
of 'personality'. Developmental Psychobiology, 53, 521–548. https://doi.org/10.1002/dev.20544
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[Highlights]
Last update: 16.02.2014
Keywords: personality differences, behavioral types,
dispositions, responsivity, individual differences, animal
personalities, personality differences, individuality, personality
factors, behavioral styles, personality, behavioral profile,
temperament, coping style, behavioral strategy, correlated traits,
reactivity, behavioral syndromes.
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