Cognitive Processing in Bird Song Development and Use Psych 1090 Lecture 10.
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Transcript of Cognitive Processing in Bird Song Development and Use Psych 1090 Lecture 10.
Cognitive Processing in Bird Song Development
and Use
Cognitive Processing in Bird Song Development
and Use
Psych 1090
Lecture 10
Oscine birds learn their songs, just like human children learn their
language…..
Clearly, there are innate predispositions to learn both song and
languageand particular brain areas are involved
in the processes for both birds and humans
But learning does occur…..and usually involves some cognition
And, as we’ll see, it isn’t only what the bird learns that is
important
but also the way it chooses to use its vocalizations
the choice of which song to sing or the way in which it is sung can
have significant effects on other birds
But, with respect to aquisition, birds need to learn
from one’s neighbors
what constitutes the communication code
which notes or songs to sing
what order in which to sing them
from whom to learn the code
from one’s father
from a combination of tutors
And, it appears that all these behavior patterns involve, to some
degree, some forms of cognitive processing
And how to use the communication code
to recognize individuals
to attract mates
to defend territories
Specifically, the natural world is an extremely complicated place
of myriad interactions--
some obvious, some hidden--
but all of critical importance if one is to understand its
workings
Information must be processed, sorted, ignored or acted upon by
all creatures
And, as we’ve said before, fully programmed responses would be almost useless in dealing with a
world of myriad situations
Flexibility in processing in crucial for success
John Smith (1998) sums it up:
“…an animal has become flexible when it can process individually acquired knowledge, seek further information and hold a range of options open as it works to anticipate the course of an event. Such an individual can fine-tune and modify its responses. It can evaluate unexpected information and cope better with variable environments than can the ‘releaser-driven’ individuals posited by early ethologists.”
We’ll start with acquisition and then go on to use
But remember that these are going to be inter-related issues
for some avian specis
Looking at birds’ choice of from whom they will learn their
songs….
doesn’t necessarily reflect cognitive any levels of
processing…
Many times birds just learn to sing from their fathers…
But then they do differentiate their song enough to allow themselves
to be recognized individually
Simply because they hear their father’s song more frequently than any other song around…
So that they don’t sound like dad or their brothers
But in other cases, birds choose to learn from territorial neighbors
particularly ones that appear most dominant in the area
In such cases, cognitive processing is clear because they
evaluate the various singers
But even then the issue isn’t entirely settled
because there are factors involving whether the birds
stay where they learned their song
or disperse to another area with a different song tradition
And although “tradition” generally refers to a song
dialect
that is, a variation on the species-specific format
it can also sometimes mean that the newcomer has to fit into dominance system in a given
area
All birds do learn to something about song in
their first year
And some actually start to sing in that hatchling year
Whereas most won’t actually come into full song until they are
almost a year old…their next spring
In general, the pattern of song learning proceeds as was described by Marler and his colleagues in the
1960s:
The differences are in the details…
Different species learn at somewhat different rates, different numbers of songs, and with more
or less flexibility
but the basic pattern is the same
Birds like indigo buntings put down song memories in their first year,
but then migrate away and return to areas that are not necessarily those in
which they were hatched
they then switch their songs to replicate that of the most dominant
male in the new area
Birds like chaffinches, however, try to sound different from their
neighbors….And appear to be able to learn songs in both their first and second years….
According to recent work, they sound like neighbors who are 3 or 4
territories away….
Given that actively learning songs at such a distance is unlikely,
What probably is happening is that birds sort each other out
Now, given that some territories are better than others, one could begin to
imagine the types of dominance games that must be played in such a
situation!
and choose to nest away from neighbors that sound like they
do….
Which, if nothing else, means that both species, in different ways,
The process involves the transitive inference work we’ll discuss next
week
and suggests at least some level of cognitive processing
have to evaluate the interactions among at least some different males
in the area
We’ll talk more about such aspects in a bit…
But you also need to know something about the flexibility in the song acquisition process that
was not initially expected…
Birds were once thought to have a critical period
and also a restrictive song template
The idea was that the birds heard lots of song when they
were first hatched
because the adult birds in the area were still defending their territories
from other birds
The idea of a template was to filter out all the allospecific songs so that they wouldn’t
learn the ‘wrong’ song
And the idea of a critical period was that they’d be sure to get
song when dad was singing close to the nest, again insuring the
‘correct’ song
The template and critical period ideas came from studies done on white-crowned sparrows raised in
social isolation and given tutor audiotapes
so that researchers could control exactly what the birds heard and
when they heard it
Under such conditions, white-crowned learned best between
days 10 and 50
and ignored songs of other species that they heard on tape
But, of course, the conditions did not replicate reality
It turns out that white-crowns are much more flexible when their tutors are live:
If they hear only one tutor song to day 50, they sing that song…..
But if they have social interactions with adult birds at least up to day
100,
They will switch and sing more of the song they hear later
One can argue that what is occurring is simply an ‘overwriting’ of the
earlier song by more recent material
Or that learners are just ‘remembering’ song elements of the later tutors from some innate
storage bin….
But those explanations are not entirely enough….
First, birds that do not hear any tutor sing a totally bizarre song,
That is, some memories have to be laid down before they can be
recalled
so they can’t just create songs from innately stored material
Second, if white-crowned sparrows are put in situations with a bird that sings the original song it learned….
it will switch back to that song; that is, revert to the song it would seem to
have forgotten…..
and can actually switch back and forth between different songs depending on
what it hears
Now, one might conclude that the bird is just reacting in a species-
specific manner, replicating, tape-recorder like, what it has just
heard….But, given that white-crowned
sparrows normally sing only a single song, such behavior is not likely to
have been hard-wired in
But rather the bird is processing what it has heard and reacting
appropriately….
Other birds give clearer evidence of processing in terms of how they learn and sing their
songsparticularly when they have a very
large repertoire
large numbers of songs are both difficult to learn and difficult to
maintain in a given order so as to retain immediate variety (not repeating what was just sung)
Some of the best studied birds in this regard are nightingales
they learn strings of over 60 different songs
after singing each song, the bird is making a decision about the next song
in the sequence—
and the sequence of songs in a their song bout actually represents a
sequence of behavioral decisions
that is, the birds engages in some form of cognitive processing—and humans can abstract rules about
these decisions
Moreover, careful study has shown that the ordering of the songs is of biological importance to the singer
and not just an artifact of the analysis done by a researcher
When singing, the nightingale actually chunks its repertoire into groups (or, as the researchers say,
“packages”) of about 3-5 songs
The birds maintain the serial order of the packages but not necessarily that
of songs within each package
So researchers see a pattern like the following in terms of learning and
recall….
1-5
6-9
10-16
17-20
21-27 28-
3435-40
41-46
47-54
55-60
61-63
64-70
17
2019
18
Rendition #1
17
2019
18
Rendition #2
Further studies show conclusively that storage and production process does not simply involve paired associations
between song-types
Otherwise, birds could not go from, for example, no. 19 in one packet to no. 22 in another packet at one time, and a different between-packet order at
another time
Although Todt and Hultsch do not suggest that this intra-package ordering could be important in song-matching
which we’ll see is a critical issue for other birds that we’ll discuss
in this lecture
the possibility exists
But how do the birds learn these long lists—particularly if they hear lots of birds singing around them?
But what happens if you give a bird a long list—say, of 60 songs
or several such lists in which songs closest to one another do
not have any particular similarity…
And what if the songs were not separated in any special ways….
how would a nightingale form a repertoire of its usual 100 or 200
songs?
To figure it out, you do a series of clever experiments like those of
Todt and Hultsch
They began by exposing young nightingales to several different
long series of songs in the laboratory, called master strings
By permuting song orders in the different strings, the number of
song repetitions, and other variable such as social interaction,
they determined what was needed for the birds to acquire
the songs
and how birds ordered these songs in their singing bouts
Specifically, as would humans, the birds classified the large numbers of songs heard in master strings into smaller, more manageable
chunks.
The size of these chunks or “packages” , of three to five
songs,
and is probably constrained by short-term memory
relates directly to the chunks seen in singing
The songs in each package seem to be learned at about the
same time
and to arise early in the process of song development
and, as in the final version, song order is quite variable within the
packages
But even as the birds learn, the packages are themselves arranged
in a stable order,
and this order reflects the context, or the master string, from which the
songs were learned
This package ordering, however, in contrast to the structure of the packages themselves, emerges
relatively late in the song development process
There are no limits to the number of packages that are strung
together,
and the number is determined by the length of the master string
that the bird hears
But that’s not all: often, late in development, a nightingale invents a new set of songs…
but the set derives from those already in a given package
Interestingly, birds that hear the same master strings may
have different package boundaries
and thus somewhat different overall song order, maybe
for individual identity
but the rigorous general form of the packages will be
maintained
that is, packages never vary from the 3-5 song limits
Now, sometimes birds were given multiple master strings…
when such birds are practicing during the acquisition process,
the intervals between imitations acquired from the same master
string or context group were significantly shorter
than the intervals between imitations acquired from different
context groups.
That’s important, because it suggests how the birds store the
strings….
That is, if the time needed to access the stored
representation of song-types varies
depending on whether retrieval is from within a given context group or from a different context group…
Then there is data providing evidence for hierarchical memory and likely cognitive processing
In other words, the birds appear to be categorizing the songs with what would likely in the wild be
songs heard from a particular individual, or at a particular time or
location
Such data couldn’t be used to argue for episodic memory
directly,
but suggests the possibility…
Obviously, in the wild, they hear strings not only from their father, but also from other neighboring
males.
One possible problem was that if, in the lab, the master strings are
separated by less than five minutes and repeated only 20
times, the birds can’t remember the
context….
In the wild, the time separation is likely to be as short as 5 min…but the repetition rate is likely greater
But the number of exposures does seems to have an important effect
on song learning
Although birds can learn some songs after hearing them as few
as 5 times,
they seem to need to hear them at least 15-20 times to reproduce
them clearly
Which makes ecological sense…
Why bother to learn the song of a bird just passing through, or that
may have died?
A bird wants to learn the best set of songs from the best songster
It also seems that twenty exposures are necessary in order to get the song order down pat…
If, however, a master string is presented for something like 100
repetitions,
the package effect (variability within packages) is smoothed out
in the sense that the order of songs within the packages
becomes much more defined
and thus the overall order is more stable and the package boundaries become less
important
which is also important….
Because it suggest that birds are, indeed, using packages as an aid
to memory…
When exposures are limited, and a bird hasn’t been given much
chance to form the serial order,
it chunks information into packages much as do humans who
are faced with processing long strings of information in a limited
time
Furthermore, if the song interval within the master string is
doubled,
from a normal rate of 4 seconds to about 10,
that is, when information is given with additional time for acquisition (and likely
processing)
the birds have less need to chunk
This result again suggests that package formation, or ‘chunking’
is a cognitive process found in nightingales
And other data show even more evidence for cognitive
processing
Data obtained during the song development process suggests that
the nightingales are retrieving information from memory
and are retrieving this information in a manner
consistent with a specific pattern of storage
Early in development, nightingales produce material
that is either
easily identifiable as something they heard in a master string (identifiable patterns, IPAs)
or not (unidentifiable patterns, UPAs), which might be total
inventions
As they get older, IPAs increase and UPAs decrease….
but the birds are not randomly producing this “new” IPA
material The IPAs are temporally clumped, and new material is embedded in
existing IPAs
rather than being derived from UPAs
The pattern of storage does not, however, reflect the order
of master string input …
Material from strings heard early does not appear before
material from strings heard later
So, what does this all mean? How can we describe the
process?
Hultsch and Todt (1989c) suggest a three-part system:
short-term memory
recognition memory
submemories
Short-term memory is constrained
By both the number of items to be remembered and the time allowed for retrieving them
Thus, to retain songs from long master strings (that are presented
only ~20 times)
in short-term memory prior to transfer to long term memory…
the nightingale, like humans, segments the serially coherent
master strings into different packages of information
that is, into collections of 3-5 units
Then recognition memory identifies the songs of a package
as eithernovel (new to short-term memory)
or familiar (already in short-term memory)
if the former, the material is transferred to a submemory
The submemory processes the package into a formal unit that can then be recognized by short-term
memoryThus, for each novel master
string,a group of submemories is
formed
But what if the package is familiar?
Then recognition memory transfers the material into an existing
submemory, which is thereby strengthened
And, because long master strings are learned as effectively as short ones, even when heard only ~ 20
times processing of the group of
submemories likely occurs in parallel
However, because each package is connected to a particular context (i.e., master string)
an additional process has to be postulated
that somehow associates and connects the sets of submemories that were developed from a given
master string
As it turns out, the first exposure to each master string plays a key
role in acquisition
Birds remained fairly still and attentive during their first
exposure to a master string
and moved around more as the number of string presentations
increased
but then they quieted down when a new set of song-types—a
new master string—was presented
Habituation/dishabituation effects
Biologically, this scenario makes sense….
Pay attention to new stuff, even just new ordering of old stuff
And, of course, I haven’t even touched on the structure of the
individual songs…
It’s clear that these are incredibly complex learning issues for these
birds
Now, all this ordering is important for song retrieval as well…
In nature, birds have about one second to identify a neighbor's
song and
at the same time also select and retrieve a song of the same type
from his own repertoire
Even tho’ nightingales don’t match songs as much as other birds we’ll
discuss
They still need to be able to access what they have, and all this chunking and packaging
helpsBasically, their memory
processes seem quite like those of humans learning long
lists
And this memory form is important for other birds as
well…
List learning also appears quite important in marsh wrens….
These birds can sing from 100-400 songs in a specific order;
they share many of these songs with their neighbors
who sing them in different orders
Now, when researchers first started studying songbirds,
they assumed that large repertoires were used only to
prevent habituation
So that birds didn’t just tune one another out…and that might be
partially true for nightingales
But, as we shall see for marsh wrens (and later for song
sparrows)
such is not the case…
A lot depends on the particular song that is sung and thus
deliberate choice is important
So, each wren has to know the order of its own ~200 songs and the order of 3-4 neighbors’ ~200
songs….
Now, marsh wrens nest in fairly small territories, which means
they have 3-4 neighbors…
And they match songs to defend these territories…
In territorial disagreements, they perform a sort of marsh-wren
group poker….
Bird A will match the song of neighbor B and then sing the
next song not in his, but in B’s list….
tending to go through at least portions of their repertoire in lock-
step
Sometimes all the males in close proximity joined in, all using the
same song types
Given that each male, when singing alone, generally has a somewhat different sequence from other birds in the area,
the wrens seem to be making active choices about what to
sing based on their processing of information from the other
birds around them
they also have to recognize, if not sing,
other songs of their neighbors that are not in their own
repertoire
in order to help them recognize the particular neighbor that is
singing
So that is a huge memory and processing load
When the researchers examined the singing patterns,
They initially did so by testing only two birds in the laboratory
training them on different sequences of similar, not
identical, strings
B can chose to match this song and then continue, or just
continue
So, when B heard A sing one of his (B’s) song,
which shows that he is subordinate to A
Or B can sing the song in A’s repertoire that follows this song,
So you hear something like this…..
which shows that he is challenging A for dominance
Bird A Bird B
10
13
12
11
27
14
28
29
30
31
Bird A hears B’s 27, which is his 11; sings B’s 28, which may be his 14
B can sing his own 29, or challenge A by singing A’s 12, which could be B’s 2 or his 37…
?
And this occurs for all neighbors in the area….3 or 4
birds, generally
And this can be going on not sequentially but simultaneously
think of the speed at which these interaction have to occur and decisions have to be made
Marsh wren song rates are about 20 songs/min
up to four other males are signing at roughly the same time
So, like the nightingale, the wren may be hearing another
song every second
has to figure out what to sing in reply to that song in that 1 sec
timeframe
Possibly, too, birds in neighboring territories are eavesdropping on these
interactionsusing the information obtained to determine the relative worth of
their neighbors
Sometimes songs are altered based on feedback from the
female, as in cowbirds
Other types of input are used for choice of song…
Now, cowbirds are nest parasites, so the males have to learn their song from someone
other than dad…
So that, unlike other birds we discussed, they hear only the
‘wrong song’ in their first summer….
Thus they must choose appropriate flocks for the fall and winter
…without necessarily having seen other of their species….
They get the basics from hanging out in juvenile groups
after fledging
Then they try out their song on the various females that they
come across
And they better get the local song right…
If the male sings a song from the wrong tradition,
he’s toast
What would be of interest would be experiments to see if the
male would choose a cohort in a “bilingual” environment…
But not if another, more dominant male, is in the area
But, even in the tradition, the male will sing a number of different
songs, wait for the female to give a wing-
flip to show she likes that one
and the male will then use the preferred song almost exclusively
In an aviary, juvenile males housed with adults tended to associate primarily with other
juveniles,
But sang to adult males and adult females…
They then exhibited normal courtship and aggressive behavior
patterns
In contrast, juveniles that were put into a situation in which they did not have any interactions with
adultsbasically didn’t know to
approach females or avoid adult males in the breeding season….
Suggesting all such behavior was learned…
And, unlike juveniles w/ adult interactions,
They didn’t know what to do with their songs!
their song crystallized sooner, and were more potent….
which isn’t necessarily good when they are then put into a normal flock
They could get clobbered by the dominant males
And if adult males were housed without juveniles, who would
challenge them,
They later did not compete well amongst each other for females…
i.e.,they seemed to lack the ability to evaluate interactions—unable to perform appropriate cognitive
processing
It would seem that some level of processing exists, even if on an
unconscious level
Other experiments show how these different patterns can be affected by
change, suggesting that
The behavior develops in an ‘on-line’ manner, depending upon what is
currently happening….
Birds also appear to use some form of cognitive processing
when recognizing their neighbors…ie., same/different
Remember how tough it was to demonstrate true same/different
behavior…
Rather than simple matching behavior or other simpler actions
For song birds, natural behavior patterns of individual recognition, vocal dueling and song matching require same/difference-based
discrimination
implying that such discrimination is an adaptive trait
In the laboratory, however, behavior is not easy to demonstrate….
For example,
budgerigars’ apparent discrimination of similarities and differences in canaries’ calls may be based instead on learning the unique characteristics of individual calls similar results were found in song discrimination studies on cliff and barn swallows and great tits
That is, match-to or different-from-sample
Song sparrows appeared to make fine acoustic distinctions among conspecific
song syllables in a habituation/dishabituation experiment
but data must be interpreted carefully with respect to same/different because
these birds can memorize large numbers of song types
That is, again work on the basis of MTS or NMTS…
Studies showing how different sound features differentially affect conspecific song recognition and discrimination of conspecific from allospecific song for
each species
demonstrate just how difficult it is to design experiments to show that birds
understand same/different the way Premack would require
e.g., intro notes versus final trills
Field sparrows differentially weigh information in various song features
and thus results could depend on which feature an experimenter
chooses
Specifically, experimental design may not demonstrate a subject’s
perception of same/different
But many warblers can tell not just whether a song is from a
familiar neighbor or an unfamiliar stranger
That is, MTS…
but also whether the song from a familiar bird is coming from the
wrong territory….
And remember this information from one year to the next!
which also implies some form of spatial encoding and cognitive
processing….
At least a very good memory…
Song sparrows in the wild have a much smaller repertoire than
nightingales and marsh wrens…5-10 songs
So, to understand these birds, you need to know a bit about their
ecology
and they engage in a complex form of individual recognition…
Initially, researchers didn’t think song sparrows actually did have
individual recognition…
or even neighbor-stranger recognition
Because they would react like banshees to anything played to
them in some experiments…
And did show a neighbor-stranger difference in other
experiments..
Stoddard, in an elegant set of experiments, finally learned that the problem was that these birds had exquisite neighbor-stranger
and individual recognition
And that they were extremely sensitive to their territorial
boundaries….
So that if the experimenters played anything within their territory…
neighbor or stranger…
They got the banshee response
But IF they played the neighbor song outside the boundary,
they got a mild response
And a stronger response to the stranger…Why?
Song sparrow populations have a lot of birds called ‘floaters’…
Birds that are somewhat familiar, but that are without territories
And these floaters are always on the lookout for a territory that isn’t
well defended
So any intrusion, even by a somewhat familiar bird, is seen
as a serious threat
Now, for song sparrows, in many populations, unlike marsh wrens,
neighbors do not share song types, and therefore cannot type-match….
by using a song from his repertoire that was similar in some way the
birds recognized
But a bird lacking a true type match could still song-match a stimulus
song
So, if a bird hears a song that is similar to one or more of his songs, but an exact match to
none of them, it replies at rates significantly
above chance with whatever in its own song is the closest match…
e.g., a song with a ‘double buzz’ intro, or one with a specific type
of trill….
Again, suggesting some level of processing…
the bird cannot reflexively (or mindlessly) sing back exactly what
it heard
but somehow rather very quickly must search through its repertoire
(those 5-10 songs) to find the closest match.
Even if one argues that the bird is not basing its choice on a
complex level of same/different discrimination
but ‘merely’ on the basis of familiarity….
the task is not simple:
particularly in early spring, the territory owner can be faced with a large number of such intruders…
each of which has its own repertoire
and the owner must quickly choose the appropriate reply or
stand to lose its territory
Moreover, the intruder might try more of its repertoire in an
attempt to outsing the owner
Think of the interaction as a kind of poker game, in which you can’t
be sure of the cards that your opponents are holding….
and you begin to understand
But, of course, as the season progresses, the birds start to learn about their neighbors
And they couldn’t breed or feed young if all they did was defend
their territory
So they eventually engage in a kind of détente….
So, as they season progresses, the shift from song-type matching to repertoire matching of neighbors
In essence saying “OK, by singing something I know you know, I
don’t really need to fight you, just remind you that I am still me and
keep out”
A kind of “dear enemy” situation
Remember, the neighbor can still be a threat, and will invade
if he hears no response
So they are carefully grading their responses, carefully choosing
their songs after learning what their neighbor sings…
And they still patrol their border w/ unshared songs
To let birds in distant territories or floaters know that someone is
there w/o annoying their neighbor
But each bird has to remember the level of aggression of each
neighbor
as well as the several songs of each of its neighbors (3 or 4 of
them)
and must always be vigilant against floaters
whose songs may be somewhat familiar
Remember, the détente is based on the intimate knowledge of what
is normal and expected in the situation
and knowing when the norm is violated
None of this can easily be explained as a simple stimulus-
response
But involves a lot of information processing
And shows complexity even with a relatively small repertoire
Which is why scientists can fake them with playbacks…
Of course, the song sparrow cannot tell what bird is singing, only
something about the song that is being sung
Thus the sparrow isn’t recognizing a particular neighbor, just what
should or should not be heard from a specific location
If they hear a playback in their territory from a stranger that uses a
song very similar to that sung by their neighbor
They still respond as though to a stranger…..
Thus a floater attempting some for of deceptive mimicry would be
thwarted….Suggesting that such information
processing is evolutionarily adaptive
Studies on chickadees (a North American bird like the great tit) and
zebra finches also show that the abilities involved in individual
recognition are learned….Birds that are raised as isolates, when compared with birds that have been captured in the field take much more time to learn discriminations in the
lab….And you would think that lab-raised birds would have the advantage of familiarity with the environment….
Because great tits, like the buntings, learn their songs and adjust their songs when they arrive on their
breeding grounds,
Great tits present another interesting example of some level of
processing….Researchers found that they shifted
the frequencies of their songs in noisy urban environments
Results therefore suggest that birds learn to use a restricted range of their
spectral capacity in response to frequency-dependent interference
from local noise conditions--adjusting song to territory instead of territory to
song.
It wasn’t just a matter of genetically pre-determined singers being
selected…
Of course, at some point, genetics could come into play, but not at
present
Instead, the birds seem to have tested their songs,
found out which ones appeared to suffer from auditory masking
And selectively began to use the ‘good’ ones
They had to make the decision based on the behavior of the receivers….and
rank their songs based on these behaviors