contextualising behavioural imprinting: the relationship with associative learning

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i Abstract: Imprinting is the process by which precocial species learn the characteristics of their parents, and associative learning occurs when animals link an unconditioned stimulus (UCS) to a conditioned stimulus (CS). Yet what is the relationship between imprinting and associative learning? This has been discussed using two major assumptions in psychological literature. Firstly imprinting runs parallel to associative learning. The two processes are distinguished on basis of the specificity of imprinting, purpose, and brain localisation. Most investigations into imprinting based on this assumption give conclusions which support a complete dissociation of imprinting and associative learning, excepting the PAL phenomenon which may link the localisation of the two processes. Secondly, investigations which assume imprinting can be interwoven with associative learning on different levels have discussed their relationship in terms of imprinting being solely a form of associative or recognition learning, yet concrete conclusions cannot been made due the appearance of recognition learning elements within an associative learning model. Thus, attempts to singularly label imprinting as either linked or dissociated with associative learning (in assuming the two are parallel to one another), or that imprinting is either a form of associative or recognition learning (in assuming the two are interwoven) have not been successful. Another model which similarly assumes the interweaving of imprinting and associative learning has surfaced, yet unlike previous theories, does not seek to characterise imprinting in terms of a singular banner, and thus does not facilitate comparison with existing learning processes. It is able to link imprinting theories based on the two major assumptions by accounting for phenomena observed in their investigations. The only problem is that this model cannot generate predictions of imprinting. Thus, until this can occur, we must rely on and seek to further research into theories which characterise imprinting solely in terms of one theory. 299 words

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My IB Extended Essay (Yr 12 High school). Please reference duly.

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  • i

    Abstract:

    Imprinting is the process by which precocial species learn the characteristics of their parents, and

    associative learning occurs when animals link an unconditioned stimulus (UCS) to a conditioned stimulus

    (CS). Yet what is the relationship between imprinting and associative learning? This has been

    discussed using two major assumptions in psychological literature. Firstly imprinting runs parallel to

    associative learning. The two processes are distinguished on basis of the specificity of imprinting, purpose,

    and brain localisation. Most investigations into imprinting based on this assumption give conclusions which

    support a complete dissociation of imprinting and associative learning, excepting the PAL phenomenon

    which may link the localisation of the two processes.

    Secondly, investigations which assume imprinting can be interwoven with associative learning on different

    levels have discussed their relationship in terms of imprinting being solely a form of associative or

    recognition learning, yet concrete conclusions cannot been made due the appearance of recognition

    learning elements within an associative learning model. Thus, attempts to singularly label imprinting as

    either linked or dissociated with associative learning (in assuming the two are parallel to one another), or

    that imprinting is either a form of associative or recognition learning (in assuming the two are interwoven)

    have not been successful.

    Another model which similarly assumes the interweaving of imprinting and associative learning has

    surfaced, yet unlike previous theories, does not seek to characterise imprinting in terms of a singular banner,

    and thus does not facilitate comparison with existing learning processes. It is able to link imprinting

    theories based on the two major assumptions by accounting for phenomena observed in their investigations.

    The only problem is that this model cannot generate predictions of imprinting. Thus, until this can occur,

    we must rely on and seek to further research into theories which characterise imprinting solely in terms of

    one theory.

    299 words

  • ii

    Table of Contents:

    I. Abstract i

    II. Table of Contents ii

    III. Introduction 1

    a. What is filial imprinting? 1

    b. What is associative learning? 1

    IV. Imprinting and associative learning running in parallel 2

    a. Distinction in specificity of imprinting 2

    b. Distinction in purpose 2

    c. Distinction in localisation of function 3

    V. Imprinting as interwoven with associative learning 4

    a. Imprinting as a form of associative learning 4

    b. Searching for a neurological unconditioned stimulus 6

    c. Imprinting as a combination of associative learning and recognition learning 7

    VI. Conclusion 10

    VII. References 11

  • 1

    Introduction:

    What is filial imprinting?

    As humans, an essential part of our development is learning to recognise and attach to our parents or

    guardians. This phenomenon is also seen, and much more significant in the development of non-human

    animals. Zebra young are able to distinguish the stripes of their parents from a herd of 100; zoo-keepers

    must consider the time a mother and new-born baby spend apart so the baby panda is able to attach to the

    correct mother figure; or, if their parents are absent, geese are able to imprint on human companions, and

    cases of geese learning how to fly by direction from ultralight aircraft powered by enthusiast Bill Lishman

    have been recorded in the movie Fly Away Home. This attachment to a parental carer is called imprinting,

    and is the phenomenon by which an animal learns to recognise their parental and conspecific (of same

    species) characteristics, and has both filial (relationship with parent) and sexual (in choice of later mate)

    consequences.

    This essay will address the learning process underpinning filial imprinting, which was initially observed as

    the phenomenon in which precocial birds (species of birds whose young are relatively mature or mobile

    from moment of hatching) elicit a following response toward the first object they see whether this be a

    member of their own species or a foreign object, e.g. a human or a rotating red box. This effect can be

    replicated in an artificial setting through what is called a discrimination task, where a chick is presented

    with two visual stimuli (this can be simultaneously or in succession) one is an object with which it has

    been previously exposed and trained with, another is a novel object. Imprinting has successfully occurred

    to the trained object if the chick elicits specific behaviours such as the following response (the chick

    simply follows the object), or emits twitters toward this object. Objects such as flashing lights are often

    used as an imprinting object, as substitute for a stuffed fowl, as they elicit the same responses in chicks.

    What is associative learning?

    Associative learning (a form of which is classical conditioning) can be defined as the linkage of an

    unconditioned stimulus (UCS) to a conditioned stimulus (CS), such that the CS comes to predict the UCS.

    This carries a strong element of reinforcement, whereby the UCS is either negative or positive for the

    learner, and the CS is associated with a good or bad experience. On a very simple level, associative

    learning can be tested for by rewarding a chick for choosing a specific visual pattern (CS), and testing if

    the preference exists in the absence of reinforcement (UCS).

    Differentiating between learning processes is important in discovering its boundaries, thus furthering

    knowledge about how imprinting occurs and how a relationship between a parent and baby forms, for

    Comment [TC1]: Introduction: What is filial imprinting?

    Comment [CT2]: http://en.wikipedia.org/wiki/File:Christian_Moullec_4.jpg

    Comment [CT3]: Use quote from Lorenz original paper?

    Comment [CT4]: Add to explanation with introduction from no.9

    Comment [TC5]: What is associative learning?

    http://en.wikipedia.org/wiki/File:Christian_Moullec_4.jpghttp://en.wikipedia.org/wiki/File:Christian_Moullec_4.jpg

  • 2

    potential benefit in a zoological context. There are many papers which discuss the interplay between

    imprinting and associative learning, but a direct comparison of all these theories has not been achieved,

    thus, the research question is, what is the relationship between imprinting and associative learning?

    Imprinting and associative learning running in parallel:

    Distinction in specificity of imprinting

    Konrad Lorenz (1937) first discovered imprinting, and argued for its uniqueness, meaning it had no relation

    to associative learning apart from being categorised under the broad umbrella of learning. In this way, he

    directly compared the two processes, assuming they occurred in parallel. He proposed 4 aspects in which

    imprinting was more specific than associative learning there was a critical period in which it occurred, it

    was irreversible, an outcome of imprinting was not observed until later in life, and the object imprinted

    upon was not that to which the ultimate outcome of imprinting was made. However, at that time, sexual

    and filial imprinting had not been separated, yet now in the analysis of filial imprinting alone, the last two

    features described are not applicable, as the perception of the outcome of imprinting as being the choice

    of mate later in life stem from the idea that imprinting is a continuous process from filial recognition to

    sexual selection. This has now been adjusted to restrict the outcome of filial imprinting to be the filial

    response detailed above, and later sexual selection is excluded.

    The argument of a critical period has also been refuted in Sluckin and Salzen (1961), which demonstrated

    that the ending of an animals critical period can be prolonged by restricting the chicks early exposure to

    stimulation, and the argument of irreversibility has been disproven in studies (Salzen & Meyer, 1968)

    showing that an imprinted preference can be written over. Thus, the argument that imprinting can be

    differentiated from associative learning due to its specificity has little merit. As points of similarity between

    the two processes are not identified when merely considering the specificity of imprinting, for the purpose

    of discussing the relationship between imprinting and associative learning, Lorenzs argument will not be

    considered.

    Distinction in purpose

    On a surface level, imprinting is also compared in terms of its purpose. It is argued that the purpose of

    imprinting is to learn conspecific characteristics, which, according to Bateson (1990) is an example of

    learning to categorise; however associative learning enables predictions about the environment ..the

    job of learning to predict and control the environment is not the same as that of learning to categorize it.

    Comment [TC6]: Idea of basic?

    Comment [TC7]: Imprinting and associative learning running in parallel? Distinction in specificity of imprinting

    Comment [TC8]: Lorenz, K 1937, The Companion in the Birds World, Journal fr Ornithologie, Vol. 54, p.264-5

    Comment [TC9]: Possibly in no.8?

    Comment [TC10]: refereneced

    Comment [CT11]: However this is a very simplistic distinction

    Comment [TC12]: No.5.. referenced

    Comment [CT13]: Patrick Bateson (6 P89) Detecting causual structure may required classification, but establishing a classification does not involve an association of cause with effect

    Comment [TC14]: After this, there was A point of difference is also identified in the significance of the order of presentation of stimulus when learning to categorise information, order is insignificant, however when learning cause and effect, the cause must precede the effect, not vice versa. -- but thats somewhat futile because in imprinting, cause (CS) and effect (UCS) both appear at same time.. OH, but thats the argument - but its too early to appear here havent discussed associative learning yet

    Comment [CT15]: Same argument apparently implicit in .Associative learning is like a procedure, recognition memory is more declarative implicit on P124 Memory, Imprinting, and the Brain

  • 3

    This argument also takes the same line as an evolutionary analysis, whereby two memory systems are

    disassociated based on difference in function. This theory is proposed by Sherry and Schacter (1987),

    arguing that the systems controlling different learning processes are dissociated when they are specialized

    to such a degree that the functional problem each system handles cannot be handled by another system. In

    practice, if imprinting and associative learning can handle the problems of the other, then the occurrence

    of imprinting should improve associative learning and associative learning should improve imprinting,

    however this is not the case in Bolhuis and Johnson (1988) and Bateson and Reese (1968). Thus,

    imprinting and associative learning can be dissociated in comparison of purpose and function.

    Distinction in localisation of function

    Neural studies comparing the two processes have also argued for their dissociation. Such investigations rest

    on the assumption that if these two processes are similar, they will be localised to the same areas. Initially,

    an area of the brain called the Intermediate part of the Medial Hyperstriatum Ventral (IMHV) was

    discovered to be involved in imprinting through the accumulation of metabolic markers such as radioactive

    uracil (Horn et al., 1979), and more recently experimental studies lesioning the chick IMHV have also

    confirmed the localisation of imprinting to this area (McCabe et al. 1981 and 1982, and Takamatsu &

    Tsukada, 1985).

    For example, in a study conducted by McCabe et al. (1982), bilateral (left and right hemisphere) lesions

    were placed in the chick IMHV 3 hours after exposure to an imprinting stimulus. There were 3 other

    experimental groups in the study some chicks had hyperstriatum accessorium (HA) or lateral cerebral

    area (LCA) lesions, and there was also a sham-operated control group (undergoes the same experience as

    an operation, but no lesions are placed). 15-20 hours after the operation, they were tested in a

    discrimination task and all the chicks except for those with lesions in the IMHV showed a preference for

    the imprinting stimulus.

    One of the criticisms of using lesions to test for a difference between an experimental and control group is

    the presence of a confounding variable in the potential destruction of motor or sensory capability as caused

    by the lesion. Therefore, if a chick had indeed imprinted or was able to imprint, yet could not elicit the

    response necessary to show their preference for the imprinting stimulus, they would have failed the

    discrimination task. However, after the operation, all the chicks used in this study performed equally well

    in tests of visuomotor co-ordination, ruling out such an explanation of the findings.

    Upon discovering where imprinting is localised, its relationship with associative learning based on a shared

    localisation has been disproven in various studies, including the aforementioned McCabe et al. (1982). The

    chicks with IMHV lesions were tested in a task which required associative learning they were able to

    distinguish between two visual patterns when rewarded for making the correct choice. Associative

    learning had occurred in the absence of imprinting, proving their disparity.

    Comment [TC16]: In no.10 in references

    Comment [TC17]: Horn, G. & Johnson, M.H. 1989, Memory Systems in the Chick: Dissociations and Neuronal Analysis, Neuropsychologia, Vol. 27 (1), p.6

    Comment [TC18]: Distinction in localisation of function

    Comment [TC19]: Weiskrantz no.10 says its not just localisation p.8

    Comment [CT20]: CHECK

    Comment [TC21]: In Horn. G. 1991 .(in references)

    Comment [CT22]: ((An interesting characteristic of the role of the IMHV in imprinting is the accumulation of experimental evidence suggesting the differential roles of the right and left IMHV Cipolla-Neto et al. (1982) (or another clearer study with just unilateral or bilateral) placed either right or left lesions in chicks approximately 3 hours after exposure to an imprinting stimulus. 15-20 hours after the operation, all the chicks (with either right or left lesions) retained their preference for the imprinting stimulus, however after a second contralateral (in the other hemisphere) lesion was placed in the chicks, only those which had the first lesion placed in the right hemisphere passed the discrimination task.))

    Comment [TC23]: In Horn, G. 1991, Neural bases of recognition memory, Behavioural and Neural Aspects of Learning and Memory, Oxford Science Publications, p.

    Comment [TC24]: Where else?? - references

    Comment [TC25]: Species of chick?

    Comment [TC26]: Maybe just say lesions in other parts of brain

    Comment [CT27]: WHERE IS THE STUDY SAYING IF THIS WAS A READ-OUT MECHANISM OR OTHER??

    Comment [CT28]: BUT Johnson and Horn (1986) did not consider this to be conclusive evidence (11)

    1.Simultaneous discrimination may be easier than successive discrimination tasks i.e. method in testing imprinting and associative learning was different for associative learning, both objects were presented simultaneously but in imprinting they were presented one after other (although because all groups went through this the same problem should have affected all but I dont know if the difference between groups was significant or not) ...

  • 4

    This conclusion (that imprinting and associative learning are fundamentally different) then diminishes in

    credibility through the appearance of a process considered a form of associative learning passive

    avoidance learning (PAL). PAL is process of acquiring an avoidance reaction to an object due to negative

    reinforcement. This process was tested by taking advantage of a chicks spontaneous tendency to peck at a

    bright bead and thus allowing them to peck at a bead coated in metylanthranylate (MeA), which has an

    aversive taste. Patterson et al. (1990) and Davies et al. (1988) used different methods to inhibit the

    functioning of the chicks IMHV; however both tested whether these chicks were able to associate the

    aversive taste experienced with the bead. It was found that the chicks without a functioning IMHV did not

    refrain from pecking the bead, yet sham-operated controls or checks with other areas of the brain inhibited

    did. Thus, it appeared there was a form of associative learning that was localised to the same area of the

    brain as imprinting.

    However, there have been some explanations of why this result occurred, centred on the difference between

    the task being tested and associative learning. Firstly, the methodology of the experiments are questioned,

    as they only involved one-trial of the task and adequate exposure to the unpleasant taste of the bead was not

    achieved - chicks may have refrained from pecking after a few more trials.

    Secondly, it can be argued that PAL is different to associative learning. Inhibition from pecking a bright

    bead requires declarative recognition due to it being the reverse of the chicks spontaneous tendency to

    peck. All other associative learning tasks tested natural responses such as looking for food or recognising

    visual patterns, however the credibility of these explanations has not been tested.

    Thus, theories assuming imprinting as a process running parallel to associative learning has offered mainly

    evidence against a close relationship between these two processes, however there may be some possibility

    for a link in terms of the form of associative learning, PAL, being localised to the same region of the brain

    governing imprinting.

    Imprinting as interwoven with associative learning:

    The other main view of imprinting is that it can be considered in terms of other learning frameworks, and

    not directly compared to them the two main frameworks are imprinting as a form of recognition learning

    or associative learning. In some literature, perceptual learning (van Kampen, 1993) or exposure learning

    (Sluckin, 1973) has been used instead of the term recognition learning, however both have the essential

    characteristic of arguing imprinting is the learning of an animal to recognise their parents, involving the

    formation of a mental representation without reinforcement. For the purpose of this essay, recognition

    learning will be as a blanket term for such theories.

    The distinction between these two frameworks is well-characterised in the following quote from van

    Comment [CT29]: Also called acquisition of a negative preference

    Comment [TC30]: In G.Horn no.12?

    Comment [CT31]: (before the training of the PAL task)

    Comment [TC32]: Cite study

    Comment [TC33]: Another word?

    Comment [TC34]: Imprinting as a layer relationship?? Imprinting as recognition or associative learning A distinction in terms of purpose

    Comment [TC35]: True, yes?

  • 5

    Kampen (1993) The perceptual-learning hypothesis of filial imprinting assumes that the level of arousal

    [when perceiving the imprinting object] affects the formation of an internal representation of the imprinting

    object, while the associative-learning hypothesis assumes that the internal representation also becomes

    associated with the physiological state of the moment, that is, the reinforcing properties of the

    unconditioned stimulus function by altering the chicks physiological state.

    The assumption underlying the analysis of recognition learning arguments is that, if imprinting is

    interpreted under such a framework, then the relationship between imprinting and associative learning is

    limited to a mutual categorisation under the broad umbrella of learning. It should be noted that some

    theorists do not agree with this, van Kampen (1993) argues that associative learning theory does not

    necessarily contradict recognition learning theory, they can be interwoven.

    Imprinting as a form of associative learning

    There are several arguments for the consideration of imprinting in terms of an associative learning or

    recognition learning framework. The most researched argument is that imprinting can be understood

    through an associative learning framework, and imprinting is a type of associative learning in which a

    chick associates a conditioned stimulus (CS) with an unconditioned stimulus (UCS). Hoffman and his

    colleagues (1972, 1973a, 1973b, 1978, 1983, 1987) developed a theory of what the conditioned and

    unconditioned stimulus in imprinting would be the conditioned stimulus is called E1, (the conspicuous

    characteristics of the imprinting object), and the E2 is an unconditioned stimulus, possibly a

    motivationally significant event experienced as a direct result of imprinting.

    The major problem with this interpretation is that upon receiving stimulus of the imprinting object, a chick

    would experience both E1 and E2, and the object acts as its own reinforcing stimulus. This makes the

    proposed model of imprinting difficult to investigate, although scientists have tested if phenomena

    exhibited as a result of associative learning can also be exhibited in imprinting this would mean

    imprinting carries an essential associative learning principle. These phenomena include overshadowing and

    blocking. Overshadowing occurs when several E1s (CS) are paired with one E2 (UCS); the E1s which have

    been presented separately from the others is more strongly associated with the E2 than E1s which have

    been presented as part of a compound stimulus (many E1s at once) the E1s presented separately are said

    to overshadow the others. Blocking occurs when an E1 that has already been paired with an E2 before

    being presented as part of a compound stimulus blocks the association of the other members of the

    compound stimulus from being associated with the E2.

    Experiments employing this paradigm have had some success. For example, de Vos and Bolhuis (1990)

    tested for blocking by conducted an experiment with two conditions one group of chicks was exposed to

    two yellow cylinders (YY), another group was exposed to two red cylinders (RR) the prior exposure.

    Comment [CT36]: Create a link to behavioural explanation here, to make clear Perhaps reinforce that perceptual learning theory doesnt refute associative learning theory? the second is an extension of the first? linked below

    Comment [CT37]: van Kampen p.118

    Comment [CT38]: Should I list them, saying four? YES, I think only 2 though?

    Comment [TC39]: Do principles of associative learning also underlie imprinting?

    Comment [CT40]: Give all the years P 317 (4) **** ask about referencing

    Comment [CT41]: the most successful of which is ______

    Comment [TC42]: Join together somehow if needed

    Comment [CT43]: Also say others have been theorized (movement, however it was disproven as still can imprint on stationary objects (P 317-318 (4), low anxiety state (operant conditioning Moltz, 1960 P324 (4) has this gotten anywhere)

    Comment [TC44]: Note from plan: The imprinting object is the reinforcing stimulus in itself (creates problems when trying to test it) Patrick Bateson (__) , and also Campbell, B.A. and Pickleman, J.R. (1961) Hoffman?

    Comment [CT45]: Are the explanations clear enough?

    Comment [TC46]: referenced

  • 6

    After six days of exposure, the cylinders for both groups were replaced for seven days by one blue and one

    yellow cylinder (YB). After all this, when both groups were exposed to a single blue cylinder (B), the RR

    group spent more time with it. This suggests that when exposed to the YB cylinders, the YY group had

    blocked an association with the blue cylinder as they had already be exposed to a yellow one. In a similar

    manner, overshadowing was reported in a study conducted by Hoffman et al. (1972).

    In evaluation, these experiments have a major flaw the apparent result of blocking or overshadowing may

    merely be due to incidentally more attention given to one or the other stimulus when experiencing a

    compound stimulus the stimuli were physically disparate and chicks could only concentrate on one at a

    time. Solutions to this have been suggested (Bolhuis, de Vos & Kruijt, 1990) in the form of presenting a

    combination of auditory and visual stimuli have been suggested, so that the chick does not need to give

    selective attention to one or the other as a chick does not stop listening to one stimulus in order to listen to

    another. However, such experiments employing this methodology have not been conducted.

    Searching for a neurological unconditioned stimulus

    Yet, these experiments, simply establish the existence of a UCS, but what not what it is, which is where

    neural interpretations become important. Hoffman and Segal (1983) theorised the presence of a pleasure

    centre co-ordinating the motivationally significant event. Thus, the unconditioned stimulus is the

    stimulation of the pleasure centre. This theory can be supported if filial response can be heightened by

    increasing the intensity of the imprinting stimulus. This has been shown in a study by Jackson and Bateson

    (1974) whereby changing the colour of a visual stimulus presented to chicks that were predisposed to react

    to certain colour, changes the likelihood they would step onto pedal to be exposed to the imprinting

    stimulus (the filial response). However, this depended on the length of pre-exposure to the coloured

    stimulus.

    It is, however, not known what chemicals would stimulate this pleasure centre. It was suggested that the

    catecholamine neurons worked as reward neurons. More specifically, Davies, Horn and McCabe (1983)

    found that exposure to artificial imprinting stimulus was connected with widespread elevation of

    noradrenaline level in the chick brain, but not with variations in dopamine level. Furthermore, depleted

    levels of noradrenaline in the chick forebrain increase the time taken for imprinting to occur (Davies,

    Johnson & Horn, 1992).

    However, by increasing when imprinting occurs, the role of neurotransmitters as reinforcers support both

    an associative learning and recognition learning framework for imprinting. White and Milner (1992)

    theorised that reinforcers had the potential to 1. To enhance the formation of neural representations. Here,

    the purpose of the reinforcer is to give arousal, enabling memory formation, thus being closer to a

    recognition learning interpretation of imprinting. 2. To endow a stimulus with motivational properties,

    Comment [CT47]: Significantly??? Have a look** (7)

    Comment [TC48]: referenced

    Comment [CT49]: Although mixed in with some unexpected ones P322 (4)

    Comment [CT50]: What does this mean for the results?? Bolhuis, De Vos and Kruijt suggested combination of auditory and visual stimuli - have there been any studies??? Look** Called the sensory-orientation hypothesis p.113 van Kampen

    Comment [TC51]: referenced

    Comment [CT52]: ******Also use transfer of training/stimulus generalisation as evidence (Bateson P96 (6))??

    Comment [TC53]: Searching for a more detailed explanation a neurological UCS?

    Comment [TC54]: referenced

    Comment [TC55]: referenced

    Comment [CT56]: Studies found in vanKampen p.117 referenced

    Comment [CT57]: Also supported by this study: Dudai (1989) Noradrenaline has been shown to facilitate long0term potentation (LTP), a neuronal phenomenon suggested to be the first stage in mammalian learning. It has been shown that NMDA receptors and glutamate are involved in LTP in the mammalian hippocampus, and also in neural changes in the IMHV related to imprinting. These parallel findings lead to the suggestion that the first stages of memory formation in imprinting may well involve LTP-like cellular changes, and, one step further, that they may be modulated by noradrenaline. van Kampen p.119

    Comment [TC58]: referenced

  • 7

    which would facilitate the formation of an association between the imprinting stimulus and the appropriate

    response, closer to an associative learning interpretation of imprinting. Yet, despite the potential presence

    of recognition learning, neurotransmitters are still considered reinforcers in a CS-UCS context reinforcers

    which would enhance recognition learning. Recognition and associative learning would appear on different

    levels in imprinting.

    Thus, the position of each neurotransmitter in terms of behavioural models is ambiguous. Research has

    been conducted as to the effects of neurochemical factors on imprinting as a whole, yet research into the

    pathway by which this effect is triggered is yet to surface; and perhaps the pathway is not solely

    recognition or associative but a combination of both on various levels.

    Imprinting as a combination of associative learning and recognition learning

    This sort of an argument, combining aspects of both recognition (perceptual) and associative learning, so

    associative learning would be a component of imprinting is proposed in the Bateson and Horn (1994)

    model of imprinting. Essentially, it proposes three sub-processes that sequentially analyse the features of

    stimuli, recognize those feature combinations that are familiar and organize appropriate responses. Those

    three sub-processes are Analysis, Recognition and Executive respectively. Figure 1 shows a simple

    version of the model where there are 2 Analysis modules, 2 Recognition modules and 1 Executive module.

    The overall model is a neural net, and there would be many more modules forming a layer of Analysis

    modules connected to a layer of Recognition modules, etc. in a real chick.

    Figure 1:

    Caption: A module is represented by a single square. A system is composed of many modules. from Bateson and

    Horn (1994)

    Analysis modules act as detectors of the features of a stimulus and work to decompose the sensory input

    into a variety of features, such as lines, orientation, direction of movement and colour. One Analysis

    module corresponds to one feature, and also transmits onwards the intensity with which each of the

    Comment [TC59]: Can also add A further problem in investigating these pathways is that the distinction between them is becoming increasingly blurred some researchers have even suggested all learning Is associative learning. Scientific consensus must be reached before any further research occurs in this area.

    Comment [TC60]: Imprinting as a combination of recognition and associative learning.

    Comment [TC61]: referenced

    Comment [CT62]: * But it is considered to be a perceptual learning theory P122 van Kampen But also incorporates elements of perceptual learning which are [expand]

    Comment [CT63]: Mention thickness of lines.. (give a key)

    Comment [TC64]: Caption: A module is represented by a single square. A system is composed of many modules.

  • 8

    feature detectors has been activated, or in other words how strongly a detected feature corresponds with

    the chicks store of the imprinted stimulus.

    This transmits onto a Recognition module. A Recognition module consists of an excitatory unit (P-unit),

    and an inhibitory (I-unit) but this discussion will only feature excitatory units in discussing the formation of

    associations. Bateson and Horn (1994) say A key feature of our model is the spontaneous [i.e. random]

    fluctuation of excitability in the plastic (P) units of the Recognition system and the excitability of the P

    units within different Recognition modules are not synchronised. This is based on the finding of

    spontaneous neural activity in the IMHV of both imprinted and non-imprinted chicks as detected by a

    micro-electrode in Payne & Horn (1984), Davey & Horn (1991) and Brown & Horn (1994). When a P unit

    is at a high level of excitability, a given input from an Analysis module is most likely to activate it, and this

    connection between a unit in the Analysis module and the P unit in the Recognition module is strengthened

    when the two units are conjointly active; the more frequent this conjoint activation occurs, the stronger the

    connection is herein lies the fundamental associative learning principle. Although the random excitability

    of the P units of the Recognition module makes it seem unlikely a strong association can form to a specific

    P unit, it is proposed that a P unit remains in a heightened excitability for a finite period after activation,

    allowing for such a connection to form.

    Modules in the Executive system control the filial approach behaviour of chicks and can be activated by

    modules in the Analysis system or Recognition system. Units in the Executive module initially (before

    imprinting) hold a maximum connection with units in the Analysis module, representing the predisposition

    of chicks to approach certain objects rather than others. However, as a result the conjoint activation of a P

    unit in the Recognition module and a unit in the Analysis module, resulting in the activation of an

    Executive module, the 3 connections between them are all strengthened, and the Recognition modules

    rapidly gain effective control of the Executive module, enabling control over the filial approach

    behaviour.

    Comment [TC65]: referenced

    Comment [TC66]: referenced

    Comment [TC67]: Possibly cite source which also says this

    Comment [TC68]: Word better?

    Comment [CT69]: accounting for?? similar word..

    Comment [CT70]: Still need to cover the inactivation rule and the Recognition modules storing information and the likelihood of Analysis modules to activate Recognition modules (talk about together)

  • 9

    Figure 2:

    Caption: Diagram (a) in this figure shows what happens after exposure to a stimulus that activated Analysis module,

    A1. The spontaneous excitability of the P unit in recognition module, R2, happened to be higher than that in R1 at

    the time when the input from A1 arrived, so the units in A1 and R2 were conjointly active, increasing the strength of

    the connection between them (represented by the thickened lines). At the same time, the state of excitation of a P unit

    in the Executive module E was enhanced by the direct link with A1, and as a result of conjoint activation with the P

    unit in R2, the connection between them is also strengthened.

    Diagram (b) in this figure illustrates what happens after the process of imprinting is complete, and the A1-R2 and R2-

    E connections are at full strength and the A2-R2 and A2-E connections have disappeared, however have the potential

    to re-appear if they are conjointly active imprinting is reversible. from Bateson and Horn (1994)

    In evaluation, this model has been deemed supportive of associative learning by van Kampen and de Vos

    (1995) as the premise that the connection between the recognition and the executive system is

    strengthened as a result of conjoint activityis what is generally accepted to the basis of all associative

    learning. However in van Kampen (1993) it was heralded as a perceptual-learning model, (i.e.

    recognition learning) as it carried elements of recognising and storing representations of the imprinting

    object. Thus, the model includes certain aspects of both recognition and associative learning concepts. This

    model is able to account for phenomena observed in a solely associative-learning interpretation of

    imprinting (e.g. blocking, overshadowing), and takes PAL in an imprinting context. Furthermore, evidence

    used to support dissociation between imprinting and associative learning when assuming they run parallel

    to one another can also be accommodated in this theory. The fact that associative learning occurs and

    imprinting cannot when in the IMHV is lesioned may be due to the IMHV accommodating the

    Recognition modules, however the Executive modules would still be activated and join with the

    Analysis modules. A major problem, however, is the little experimental evidence to justify the model and

    that the learning rules are far too obscure to allow for specific predictions to be derived from them.

    Comment [TC71]: van Kampen, H.S., de Vos, G.J. 1995, A Study of Blocking and Overshadowing in Filial Imprinting, The Quarterly Journal of Experimental Psychology, Vol. 48B (4), p.353

    Comment [TC72]: ***why??

    Comment [TC73]: Say by performing classification-together effect or too complicated? Idea reference: Bateson what must be known in order to understand imprinting

    Comment [CT74]: But can the evidence for this (i.e. overshadowing and blocking) still apply to this model?

    A model of the classification-together effect has been constructed by Patrick Bateson account for what happens in the real world benefit of greater accuracy no. 6 p.89-90

    But are they the same thing?? Not really classification-together effect enables phenomenon of overshadowing but it is the overshadowing that is more important in showing that UCS exists. Although, the very fact that a classification-together (more like classification-apart) effect can be applied to imprinting means that a chick can imprint to 2 conditioned stimuli at one time, thus enabling it to be tested out. is this important in terms of a `development of a model of how imprinting occurs though??

    Comment [TC75]: Possibly reference the section ^?

    Comment [TC76]: Or system

    Comment [TC77]: Say that interpretation that imhv lesions show NOT associative learning is not true (from no.12 p.225)

    Comment [TC78]: vanKampen p.122

  • 10

    Conclusion:

    There have been two major types of theories modelling imprinting assuming imprinting is parallel and

    can be directly compared to associative learning, or imprinting as being interwoven with associative

    learning on various levels. The Bateson and Horn (1994) model is a stand-out from the second category as

    it explains both an associative-learning-alone interpretation of imprinting (also accounting for PAL), and

    findings of lesion studies assuming a parallel between imprinting and associative learning, thus linking

    these two types of theories. In this way, purely for the purposes of characterising imprinting, this model can

    be considered superior.

    Yet in terms of contextualising imprinting, when directly comparing imprinting and associative learning

    and assuming the two processes run in parallel, most evidence points to a distinction between the two;

    when assuming imprinting is interwoven with associative learning, most research displays a foundation on

    the basic associative learning principle, however is unclear if this entails that imprinting is a form of

    associative learning, or if there are additional elements (i.e. recognition learning) perhaps overshadowing

    the salience of associative learning as the primary learning process underpinning imprinting, or if

    imprinting should incorporate both associative learning and these other elements.

    This problem is primarily due to the models theorised being too complex for application of a simple

    definition processes of recognition and associative learning can be observed in various levels within these

    models. Therefore, it is perhaps not wise to attempt to categorise imprinting under a single banner.

    Although this would prevent a simple contextualisation of imprinting in terms of existing learning theories,

    it is not all-important in developing an understanding of imprinting itself. What is more important is an

    accurate model which is able to account for phenomena studied and generate predictions, which is partially

    provided by Bateson and Horn (1994). Thus, unless the Bateson and Horn (1994) model can provide

    reliable predictions of imprinting, the best method of understanding the phenomenon is by comparing it to

    associative and recognition learning processes which, through comparisons to humans, we have greater

    knowledge.

    Comment [CT79]: This is essentially my analysis can I use I?

    Comment [TC80]: Apart from PAL

    Comment [TC81]: So imprinting can be characterised as recognition learning

  • 11

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