Curiosity (from
Latin
curiosus "careful,
diligent, curious," akin to cura "care")
is a quality related to inquisitive thinking such as
exploration, investigation, and
learning, evident by observation in
human and
many animal
species[citation
needed]. The term can also be used to denote the
behavior itself being caused by the emotion of curiosity. As this
emotion represents a thirst for knowledge, curiosity is a major driving
force behind scientific research and other disciplines of human study.
Causes
Children peer over shoulders to see what their friends are
reading.
Although many living beings have an innate capability of curiosity,
it should not be categorized as an
instinct because it is not a
fixed action pattern; rather it is an innate basic
emotion
because while curiosity can be expressed in many ways, the expression of
an instinct is typically more fixed and less flexible. Curiosity is
common to
human beings at all ages from
infancy[1]
through
adulthood,[2]
and is easy to observe in many other
animal
species. These include
apes,
cats, and
rodents.[3]
Brain
Although the phenomenon of curiosity is widely regarded, its neural
correlates still remain relatively unknown. However, recent studies have
provided insight into the neurological mechanisms that may be associated
with curiosity, such as
learning,
memory,
and
motivation. Such research aims to transition the study of curiosity
from a speculative realm to one of more scientific credibility. Various
theories have been proposed in order to elucidate the mechanism of
curiosity:
Curiosity-drive
model
The curiosity-drive model states that experiences that are novel and
complex create a sensation of uncertainty in the brain, a sensation
perceived to be unpleasant. Curiosity acts as a means in which to dispel
this uncertainty. By exhibiting curious and exploratory behavior,
organisms are able to learn more about the novel stimulus and thus
reduce the state of uncertainty in the brain. However, this model does
not account for the observation that organisms display curiosity even in
the absence of exciting and new stimuli.[4]
This type of exploratory behavior is common in many species. Take the
example of a human toddler who, if bored in his current situation devoid
of arousing stimuli, will walk about until something interesting is
found. The observation of curiosity even in the absence of novel stimuli
pinpoints one of the major shortcomings in the curiosity-drive model.
Optimal arousal
model
The optimal-arousal model of curiosity posits that the brain aims to
maintain an optimal level of arousal. If the stimulus is too intensely
arousing, a “back-away” type behavior is engaged. In contrast, if the
environment is boring and lacks exciting stimuli, exploratory behavior
will be engaged until something optimally arousing is encountered. In
essence, the brain is searching for the perfect balance of arousal
states.[4]
This model aptly addresses the observation that organisms display
curiosity even in the absence of novel and exciting stimuli. While this
theory addresses some discrepancies in the curiosity-drive theory, it is
not without fault. If there is an ideal state of curiosity that should
be maintained in the brain, then gaining new knowledge to eliminate that
state of curiosity would be considered counter-productive.
Integration of reward pathway
Taking into account the shortcomings of both curiosity-drive and
optimal-arousal models, there have been attempts to integrate the
neurological aspects of reward, wanting, and liking into a more
comprehensive theory for curiosity, one that is explained by biological
processes. The act of wanting new information involves mesolimbic
dopamine activation, which assigns an intrinsic value to that new
information that the brain then interprets as a reward. This is the
neurobiology that motivates exploratory behavior. In addition,
opioid
activity in the nucleus accumbens evaluates stimuli and attaches an
immediate value to the novel object, a sensation known as ‘liking’. This
liking stimulates pleasure. The chemical processes of both wanting and
liking play a role in activating the reward system of the brain, and
perhaps in curious tendencies as well.[4]
Neurological
aspects
Due to the complexity of the subject, focusing on specific neural
processes within curiosity can help in better understanding the
phenomenon of curiosity as a whole. The following neural aspects can be
thought of as essential sub-functions of curiosity:
Attention
Attention is the cognitive process by which one can selectively
focus and concentrate on particular stimuli in the surrounding
environment. There may be many stimuli in the surrounding area, but as
there are limited cognitive and sensory resources, attention allows the
brain to better focus on what it perceives to be the most important or
relevant of these stimuli. Scientists can measure the amount of
attention an individual devotes to a stimulus by tracking eye movements.
Organisms focus their eyes on stimuli that are particularly stimulating
or engaging; the more attention a stimulus garners, the more frequent
the eye will be directed towards that stimulus. Normal individuals will
look at new stimuli at least two to three times more often than familiar
or repetitive stimuli. Exciting or novel stimuli demand more attention
than stimuli perceived as boring.[5]
Motivation and
reward
Dopamine Pathway in the Brain
The drive to learn new information or perform some action is often
initiated by the anticipation of
reward (an
emotional
sensation of relief and
happiness). In this way, the concepts of
motivation and
reward are intrinsically tied to the phenomenon of curiosity.
Reward can be defined as an effect of some action that positively
reinforces that behavior. Feelings of pleasure and satisfaction are
often associated with reward. There are many areas in the brain used to
process reward, such as the
nucleus accumbens, the
substantia nigra, the
striata
and the
ventral tegmental area (VTA). These structures together form the
reward pathway. There are many prominent neurotransmitters released in
the activation of the reward pathway, the most relevant of which include
dopamine,
seratonin and opioid-derived chemicals. Recent studies have shown
that dopamine may be important for the process of curiosity, most
particularly in assigning and retaining reward values for information
gained. Midbrain dopamine neurons in monkeys are activated when
determining the value of stimuli. There is some level of dopamine neuron
activation when the reward of a familiar stimulus is already known, but
perhaps more interestingly, there is a higher dopamine release when the
reward is unknown and the stimulus is novel. Additionally, reward values
were better retained (a function of both reward and memory) in monkeys
that exhibited more curious behavior.[6]
Such studies further implicate the reward pathway in curious behavior.
Memory and
learning
Memory
is the process by which the brain can store and access information.
While there is still much to be understood about both memory and
curiosity, the two neurological processes seemed to be linked. Curiosity
can be defined as the urge to seek out novel stimuli. In order to
determine if the stimulus is novel, an individual must remember if he
has encountered the stimulus before or not. Thus, memory plays an
integral role in dictating the level of novelty, and as such the level
of curiosity. While one side of the coin dictates that memory affects
curiosity, we can also flip the coin to project the converse
relationship: curiosity affects memory. As previously mentioned, stimuli
that are novel tend to capture more of our attention. Additionally,
novel stimuli usually have a reward value associated with them, the
anticipated reward of what learning that new information may bring. With
stronger associations and more attention devoted to a stimulus, it is
probable that the memory formed from that stimulus will be longer
lasting and easier to recall, both of which facilitate better
learning.
Important
structures
While the neuroscience concerning curiosity is still relatively
unknown, certain neuronal structures have been implicated in various
aspects of curiosity:
- Anterior cortices: Studies have observed through
fMRI that both the
anterior cingulate cortex (ACC) and the
anterior insular cortex (AIC) were activated in the induction of
perceptual curiosity.[7]
These regions correspond to both conflict and arousal, and as such
seem to reinforce certain explanatory models of curiosity that
include these principles.
- Striatum: The
striatum plays a role in attention and reward anticipation, both
of which are important in the induction of curiosity.
- Hippocampus and parahippocampal gyrus: The
hippocampus is important in memory formation and recall and
therefore instrumental in determining the novelty of various
stimuli. The
parahippocampal gyrus (PHG) is the area of grey matter that
surrounds the hippocampus and has recently been implicated in the
process of curiosity. In one study, subjects were asked trivia
questions and brain region activity was measured through fMRI. When
subjects learned their answers to trivia questions were wrong, there
was markedly increased activity in the PHG.[8]
Even if there was not a high level of curiosity when the question
was initially asked, levels of curiosity were raised when the
participant learned that his answer was wrong. This finding suggests
that the PHG may be involved in the potentiation or amplification of
curiosity more so than the primary induction of curiosity.
Important brain structures for curiosity:Hippocampus,
caudate nucleus, amygdala
- Amygdala: The
amygdala consists of a pair of almond-shaped structures located
deep within the medial temporal lobe. The amygdala is often
associated with emotional processing, particularly for the emotion
of fear, but is also important in memory. Certain studies suggest
that amygdala is important is processing emotional reactions towards
novel or unexpected stimuli and the induction of exploratory
behavior.[9]
However, much still needs to be explored to understand the
connection between curiosity levels and the amygdala.
- Anterior pituitary: The
anterior pituitary regulates the adrenal cortex, which releases
cortisol, among other regulatory chemicals. Although mostly
known for its role in stress, cortisol may also be associated with
curious or exploratory behavior. Studies have shown that monkeys
that have been administered small amounts of cortisol in early
adolescence will display a higher degree of novelty seeking behavior
later in life. However, the dose and frequency of cortisol
administration was important. Monkeys subjected to normal levels of
cortisol retained an average level of exploratory behavior, while
those where were subjected to too much cortisol actually had a
decrease in exploratory behavior.[10]
These findings may support in part the optimal arousal theory, in
which a small amount of stress encourages curious behavior, while
too much stress initiates a "back away" response.
- Nucleus accumbens: The
nucleus accumbens is a formation of neurons that makes up the
ventral striatum and is important in reward pathway activation.
As previously mentioned, the reward pathway is an integral part in
the induction of curiosity. The release of
dopamine in animal models has been measured in investigating
neurochemical response to novel or exciting stimuli. Dopamine
transients, an indicator of dopamine release, were measured
throughout life-stages of rats, as well as when rats were presented
with various stimuli. Scientists observed more dopamine transients
in early adolescent rats and in rats presented with novel or
unexpected stimuli.[11]
These findings suggest that dopamine release in reward anticipation
and pathway activation is tied to curiosity in both childhood and
adult stages. The fast dopamine release observed during adolescence
is particularly important, as curiosity and exploratory behavior are
the largest facilitators of learning during early formative years.
- Precuneus: The
precuneus is located in the medial area of the superior parietal
cortex and is involved in episodic memory and visuospatial
processing. In animal models, the amount of grey matter in the
precuneus was measured in normal monkeys and monkeys considered to
be highly curious and exploratory. Results found that the more
curious monkeys had a significantly higher density of grey matter in
the precuneus region,[12]
suggesting that the precuneus density has an influence on levels of
curiosity.
- Caudate nucleus: Each hemisphere of the brain contains
one
caudate nucleus, a small C-shaped region that is highly
responsive to dopamine. The caudate nucleus is another component in
the reward pathway. The role of the caudate nucleus in curiosity was
investigated by asking subjects trivia questions. fMRI was used to
measure brain activity during the question period. Scientists
observed that the caudate "lit up" when the participant was
presented with trivia questions,[8]
indicating the anticipation of reward. In this case, the reward was
the new information gained from learning the answer to the question.
The results suggest that the caudate nucleus is relevant in the
induction of curiosity.
Impact from
disease
Left: normal brain. Right: AD afflicted brain. Severe
degeneration of areas implicated in curiosity
Different
neurodegenerative diseases can affect curiosity levels.
Alzheimer's disease (AD) is a neurodegenerative disease that affects
memory capability. Curiosity for novel stimuli might also be used as a
potential predictor for the disease.[5]
Morbid curiosity
A crowd mills around the site of a car accident in
Czechoslovakia in 1980.
A morbid curiosity exemplifies addictive curiosity. It has as
its object
death,
violence, or any other event that may cause harm physically or
emotionally (see also:
snuff film), the addictive emotion being explainable by
meta-emotions exercising pressure on the spontaneous curiosity
itself.[citation
needed] According to
Aristotle in his
Poetics we even "enjoy contemplating the most precise images
of things whose sight is painful to us". (This aspect of our nature,
often referred to as the "Car Crash Syndrome" or "Trainwreck Syndrome",
accounts for the
supposed attraction such accidents have for passers-by.)