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How do innate behaviors differ from learned behaviors? Does a behavior
have to be only innate or only learned? Can there be intermediates?
Innate behaviors are those
in which no experience with the stimulus is required for the organism to
exhibit the ‘correct’ response on the very first exposure. A learned
behavior is one in which the organism does not give the optimal response
the first time it experiences the stimulus, instead the organism will
change its behavior over time, as it gains experience with the stimulus
and the consequences of its response. Learned behaviors require
experience but not necessarily observing others.
There can certainly be
intermediates between innate and learned responses. Or some parts of a
complex behavior could be innate while other parts might be learned. For
example, many organisms that care for their newborn offspring innately
know how to take care of their babies BUT many organisms also get better
at caring for offspring as they gain experience with it. For example, a
number of birds have a lower rate of survival of their chicks for the
very first clutch and then a higher rate for the second clutch and
perhaps higher still for the third clutch.
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Watch Video
1: Life of Insects (about 8 minutes).
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Identify a stimulus and response of the ants. What types of
communication and signals are being used in this behavior?
Stimuli might include the
appearance or smell of the seed. (So visual, chemical, and maybe tactile
signals.) A response to the stimulus is to pick it up and take it back
to the next (treat it like food).
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Given the stimulus or signal you just described, give a proximate
explanation for how the stimulus leads to the response.
A proximate explanation here
would be that the sight or smell of the seed is perceived by the ant,
processed in the brain and recognized as familiar (this is food), and
then the signals are sent to respond by picking it up and returning it
to the nest.
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Reflecting on the segment about the beetle larvae and the digger bees,
do you think the behavior of the larvae is innate or learned? Explain
your reasoning.
Given that the beetle larvae
have not had any experience with the stimuli nor the opportunity to
observe this behavior, the response of the beetle larvae must be
innate.
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Watch Video
2: Wild crows in the city (about 2 minutes). In this video, is the
behavior of the crows innate or learned? Explain your reasoning.
The behavior of the crows in
this video is learned. They do not initially know that cars running over
the nut will crack it. Nor do they know at the start that using the
cross-walk will be safer! In fact, they have probably even learned to
fly high and drop the nut on a hard surface. It is experience, and
possibly observing the behavior of other crows, that has taught them
what works. Interestingly, we might consider whether a tendency for
curiosity and trying things out might be an innate feature of
crow-ness…
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Why might some behaviors be learned and others be innate? That is, can
you think of what conditions are likely to favor a behavior being innate
versus conditions that are likely to favor a learned behavior?
A behavior which must be
done correctly the first time it is needed in order for an organism to
survive is likely to be largely innate. Meanwhile, when what you
encounter in the environment might be somewhat unpredictable, then it
may be favorable to have learned behaviors, as they are able to adjust
to the circumstances that the organism faces.
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In thinking about how birdsong develops (see the short reading under
Learning), which aspects of the process do you think involve innnate
responses? Which aspects do you think involve learned responses? What is
the role of genetics? Of environment?
The response of making
vocalizations at all is likely to be innnate. But the development of a
structure to those vocalizations such that a song is produced is likely
to involve learning (under normal conditions). In the reading, the
example for this is the experiment showing that chaffinches raised
without exposure to adult males still sing but their songs are
considered abnormal (this would be an innate response). The fact that
chicks exposed to recordings of chaffinch song develop normal songs
demonstrates a learned aspect.
Genetics has a role to play
in both innate and learned behaviors as the genome encodes the proteins
that are important in perceiving stimuli and generating a response. The
example in the reading about birdsong is the FOXP2 gene, which is a
transcription factor, turning on or off other genes. Genes like FOXP2
are important in building the neural circuitry that allows an organism
to respond innately to a stimulus or to learn a response to a
stimulus.
One way in which the
environment can be crucial with learned responses involves the idea that
organisms sometimes can only learn certain behaviors at very particular
times in their growth and maturation. In some birds, there is a brief
window where song is learned while in others, new songs can be learned
throughout life. Thus, the environmental exposures experienced during
those critical windows has a huge influence on the response the organism
learns to produce.
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Consider how we know that there is a genetic basis to a behavior. Read
Sullivan (2005) about the genetics of schizophrenia (5 pages). For
example, consider the mental illness schizophrenia whose symptoms can
include altered perceptions (e.g., hallucinations, delusions), loss of
interest/motivation/enjoyment in daily life, and cognitive symptoms
(e.g., reduced attention, concentration, memory).
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Describe the quantitative evidence that supports a genetic basis for
schizophrenia. What patterns or observations suggest that genotype
influences whether or not some- one develops schizophrenia?
A number of pieces of
evidence suggest a genetic basis: