Bilişsel Psikoloji ve Bilişsel Sinir Bilimi/Bilişsel Psikoloji ve Beyin

Vikikitap, özgür kütüphane
Gezinti kısmına atla Arama kısmına atla

Şu durumu düşleyin: Genç bir adam, adı Knut olsun, masasında oturmakta, psikoloji ödevini tamamlamak için gereksinim duyduğu birtakım makaleyi okumaktadır. Sağ elinde bir fincan kahve tutuyorken sol eliyle de makaleden göz odağını yitirmeksizin şeker kabına ulaşır. Birdenbire odasının tavanına gözlerini diker ve kendine şunu sorar: "Neler oluyor burada?"

Olasılıkla herkes yukarıda anlatılana benzer deneyimler yaşamıştır. Her ne kadar ilk bakışta bu gündelik durumlarda yaşananlar heyecan verici görülmese de burada yaşananların pek çoğu özellikle Bilişsel (Kognitif) Psikoloji alanındaki öğrenciler ve araştırmacılar için ileri biçimde ilgi çekicidir. Farkında olmadığımız bu durumların yaşandığı inanılmaz biçimde büyüleyici pek çok süreci ilgilendiren çalışmalara katılmışlardır. Kabaca konuşacak olursak Knut'ın durumu bilişsel psikologlara şöyle görünürdü:

Knut'ın bir sorunu var, ödevini yapması gerekmektedir. Bu sorunu çözmek için bir sürü biliş işlevini yerine getirmelidir. Gözlerine ulaşan ışık, görsel korteksine çeşitli duraklardan geçen elektrik sinyallerine dönüştürülür. Bu sırada karmaşık sinir ağları; Knut'ın çevresindeki nesnelerin hareketlerini, boşluktaki konumlarını, biçimlerini, renklerini, kontrastlarını hesaplar ve bilgi akışını süzer. Ekrandaki lekeler ve çizgiler sözcüklere dönüşür, sözcükler anlam kazanır, anlamlar bağlama katılır, Knut'ın sorunuyla ilgisine göre irdelenir ve son olarak belki de Knut'ın belleğinde bunların bir bölümü depolanmış olur. Aynı zamanda şeker iştahı, organizmanın gereksinimlerinin kontrolünden sorumlu beyin bölgesi olan Knut'ın hipotalamusundan kabarmaya başlar. Sonunda bu iştah, Knut'ın şekerlerine ulaşmasıyla sonuçlanır.

Haydi, şimdi de bilişsel psikologların kendimizi beyin, davranış ve kuram temelinde yorumlama yöntemlerini ve bunların terminolojisini nasıl geliştirdiklerini görmek için geçmişe bir bakış atalım.

Bilişsel Psikolojinin Tarihi[değiştir]

İlk görüşler, bilginin beyinde depolandığını ileri sürmekteydi.

Rönesans ve Ötesi[değiştir]

17. yüzyılın Rönesans filozofları nativistlerle genel olarak aynı fikirdeydiler ve beynin ayrıntılı yapısını ve işlevlerini açığa çıkarmayı bile denemişlerdi. Bunun dışında deneyci düşünürlerin çok önemli fikirleri vardı. David Hume'e göre, bilginin içsel temsilleri belli kurallara uyarak biçimlenir. Bu yaratımlar ve dönüşümler emek ve zaman almaktadır. Doğrusunu söylemek gerekirse bu, bilişsel psikolojide güncel araştırmaların çoğunun temelidir. 19. yüzyılda Wilhelm Wundt ve Franciscus Cornelis Donders, 55 yıl sonra bilişsel psikolojiye daha ileri yorumlama olanağı sağlayan, bir yanıt için gerekli tepkiyi ölçmeye uygun düşen deneyler yaptılar.

20. Yüzyıl ve Bilişsel Devrim[değiştir]

20. yüzyılın ilk yarısı boyunca bilişin araştırmasında keskin bir dönüşüm meydana geldi. Burrhus Frederic Skinner gibi davranışçılar; düşünme, dikkat, bellek gibi zihnin içsel işlemlerinin kanıtlanmamış veya gözlemlenmemiş, yalnızca varsayımsal yapılar olduğunu ileri sürdüler. Bu nedenle Davranışçılar, zihinsel yapıların kimi uyarana yanıttaki araştırması ve davranışın deneysel çözümü (doğrudan gözlemlenebilir veri) kadar bağlantılı ve önemli olmadığını öne sürmüşlerdir. Watson ve Skinner'a göre insan, ancak bu yolla nesnel olarak çalışma yürütebilirdi. Psikoloji dünyasında Davranışçı Kuram'ın popülerleşmesi, yaklaşık 50 yıl sonra terk edilmek üzere zihinsel olayların ve süreçlerin incelemesine önderlik etti.

1950'lerde bilim dünyasının ilgisi yeniden bilinç, düşünme, dil işleme, imge, bellek ve dikkate yöneldi. Davranışçılığın başarısızlığa uğraması, biliş araştırmalarında "Bilişsel Devrim" adı verilen yeni bir dönemi müjdeledi. Bu durum, çeşitli iletişim kuramları gibi yeni fikirlerin doğuşu ve zaten var olan kuramların yeniden canlandırılması niteliğini taşımaktaydı. Bu kuramlar; daha önceleri oluşturulmuş bilgi kuramından ortaya çıkmış, iletişimin kuramsal ve uygulamalı anlayışını oluşturmak için dikkat ve sinyal belirlemede deneylere önayak olmuştur.

Çağdaş dil bilimciler, bilişsel süreçlerle ilişkili olan dil ve gramer yapısı üzerine yeni kuramlar önerdiler. Chomsky’nin Üretken Gramer ve Evrensel Gramer Kuramı, önerilen dil hiyerarşisi ve Skinner'ın "Sözel Davranış" eleştirisi, Bilişsel Bilim'in geçmişinde birer dönüm noktasıdır. Bellek kuramları ve bunların örgütlenme modelleri başka bilişsel süreçlerin modellerinin oluşmasını sağladı: Bilgisayar bilimi, özellikle de yapay zeka, yeniden gözden geçirilmiş temel problem çözme ve bellek işleme-depolama kuramları, dil işleme ve dil edinimi.

For clarification: Further discussion on the "behaviorist" history.

Although the above account reflects the most common version of the rise and fall of behaviorism, it is a misrepresentation. In order to better understand the founding of cognitive psychology it must be understood in an accurate historical context. Theoretical disagreements exist in every science. However, these disagreements should be based on an honest interpretation of the opposing view. There is a general tendency to draw a false equivalence between Skinner and Watson. It is true that Watson rejected the role that mental or conscious events played in the behavior of humans. In hindsight this was an error. However, if we examine the historical context of Watson's position we can better understand why he went to such extremes. He, like many young psychologists of the time, was growing frustrated with the lack of practical progress in psychological science. The focus on consciousness was yielding inconsistent, unreliable and conflicting data. Excited by the progress coming from Pavlov's work with elicited responses and looking to the natural sciences for inspiration, Watson rejected the study of observable mental events and also pushed psychology to study stimulus-response relations as a means to better understand human behavior. This new school of psychology, "behaviorism" became very popular. Skinner's school of thought, although inspired by Watson, takes a very different approach to the study of unobservable mental events. Skinner proposed that the distinction between "mind" and "body" brought with it irreconcilable philosophical baggage. He proposed that the events going on "within the skin", previously referred to as mental events, be called private events. This would bring the private experiences of thinking, reasoning, feeling and such, back into the scientific fold of psychology. However, Skinner proposed that these were things we are doing rather than events going on at a theorized mental place. For Skinner, the question was not of a mental world existing or not, it was whether or not we need to appeal to the existence of a mental world in order to explain the things going on inside our heads. Such as the natural sciences ask whether we need to assume the existence of a creator in order to account for phenomena in the natural world. For Skinner, it was an error for psychologists to point to these private events (mental) events as causes of behavior. Instead, he suggested that these too had to be explained through the study of how one evolves as a matter of experience. For example, we could say that a student studies because she "expects" to do better on an exam if she does. To "expect" might sound like an acceptable explanation for the behavior of studying, however, Skinner would ask why she "expects". The answer to this question would yield the true explanation of why the student is studying. To "expect" is to do something, to behave "in our head", and thus must also be explained.

The cognitive psychologist Henry Roediger pointed out that many psychologists erroneously subscribe to the version of psychology presented in the first paragraph. He also pointed to the successful rebuttal against Chomsky's review of Verbal behavior. The evidence for the utility in Skinner's book can be seen in the abundance of actionable data it has generated, therapies unmatched by any modern linguistic account of language. Roediger reminded his readers that in fact, we all measure behavior, some simply choose to make more assumptions about its origins than others. He recalls how, even as a cognitive psychologist, he has been the focus of criticism for not making more assumptions about his data. The law of parsimony tells us that when choosing an explanation for a set of data about observable behavior (the data all psychologists collect), we must be careful not to make assumptions beyond those necessary to explain the data. This is where the main division lies between modern day behavior analysts and cognitive psychologists. It is not in the rejection of our private experiences, it is in how these experiences are studied. Behavior analysts study them in relation to our learning history and the brain correlates of that history. They use this information to design environments that change our private experience by changing our interaction with the world. After all, it is through our interaction with our relative world that our private experiences evolve. It is a far cry from the mechanical stimulus-response psychology of John Watson. Academic honesty requires that we make a good faith effort to understand what we wish to criticize. Henry Roediger pointed out that many psychologists understand a very stereotyped, erroneous version of psychology's history. In doing so they miss the many successful real world applications that Skinner's analysis has generated.

Neuroinformatics, which is based on the natural structure of the human nervous system, tries to build neuronal structures by the idea of artificial neurons. In addition to that, Neuroinformatics is used as a field of evidence for psychological models, for example models for memory. The artificial neuron network “learns” words and behaves like “real” neurons in the brain. If the results of the artificial neuron network are quite similar to the results of real memory experiments, it would support the model. In this way psychological models can be “tested”. Furthermore it would help to build artificial neuron networks, which posses similar skills like the human such as face recognition.

If more about the ways humans process information was understood, it would be much simpler to build artificial structures, which have the same or similar abilities. The area of cognitive development investigation tried to describe how children develop their cognitive abilities from infancy to adolescence. The theories of knowledge representation were first strongly concerned with sensory inputs. Current scientists claim to have evidence that our internal representation of reality is not a one-to-one reproduction of the physical world. It is rather stored in some abstract or neurochemical code. Tolman, Bartlett, Norman and Rumelhart made some experiments on cognitive mapping. Here, the inner knowledge seemed not only to be related to sensory input, but also to be modified by some kind of knowledge network modeled by past experience.

Newer methods, like Electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) have given researchers the possibility to measure brain activity and possibly correlate it to mental states and processes. All these new approaches in the study of human cognition and psychology have defined the field of Cognitive Psychology, a very fascinating field which tries to answer what is quite possibly the most interesting question posed since the dawn of reason. There is still a lot to discover and to answer and to ask again, but first we want to make you more familiar with the concept of Cognitive Psychology.

What is Cognitive Psychology?[değiştir]

The easiest answer to this question is: “Cognitive Psychology is the study of thinking and the processes underlying mental events.” Of course this creates the new problem of what a mental event actually is. There are many possible answers for this:

Let us look at Knut again to give you some more examples and make the things clearer. He needs to focus on reading his paper. So all his attention is directed at the words and sentences which he perceives through his visual pathways. Other stimuli and information that enter his cognitive apparatus - maybe some street noise or the fly crawling along a window - are not that relevant in this moment and are therefore attended much less. Many higher cognitive abilities are also subject to investigation. Knut’s situation could be explained as a classical example of problem solving: He needs to get from his present state – an unfinished assignment – to a goal state - a completed assignment - and has certain operators to achieve that goal. Both Knut’s short and long term memory are active. He needs his short term memory to integrate what he is reading with the information from earlier passages of the paper. His long term memory helps him remember what he learned in the lectures he took and what he read in other books. And of course Knut’s ability to comprehend language enables him to make sense of the letters printed on the paper and to relate the sentences in a proper way.

This situation can be considered to reflect mental events like perception, comprehension and memory storage. Some scientists think that our emotions cannot be considered separate from cognition, so that hate, love, fear or joy are also sometimes looked at as part of our individual minds. Cognitive psychologists study questions like: How do we receive information about the outside world? How do we store it and process it? How do we solve problems? How is language represented?

Cognitive Psychology is a field of psychology that learns and researches about mental processes, including perception, thinking, memory, and judgment. The mainstay of cognitive psychology is the idea where sensation and perception are both different issues.

Relations to Neuroscience[değiştir]

Cognitive Neuropsychology[değiştir]

Of course it would be very convenient if we could understand the nature of cognition without the nature of the brain itself. But unfortunately it is very difficult if not impossible to build and prove theories about our thinking in absence of neurobiological constraints. Neuroscience comprises the study of neuroanatomy, neurophysiology, brain functions and related psychological and computer based models. For years, investigations on a neuronal level were completely separated from those on a cognitive or psychological level. The thinking process is so vast and complex that there are too many conceivable solutions to the problem of how cognitive operation could be accomplished.

Neurobiological data provide physical evidence for a theoretical approach to the investigation of cognition. Therefore it narrows the research area and makes it much more exact. The correlation between brain pathology and behaviour supports scientists in their research. It has been known for a long time that different types of brain damage, traumas, lesions, and tumours affect behaviour and cause changes in some mental functions. The rise of new technologies allows us to see and investigate brain structures and processes never seen before. This provides us with a lot of information and material to build simulation models which help us to understand processes in our mind. As neuroscience is not always able to explain all the observations made in laboratories, neurobiologists turn towards Cognitive Psychology in order to find models of brain and behaviour on an interdisciplinary level – Cognitive Neuropsychology. This “inter-science” as a bridge connects and integrates the two most important domains and their methods of research of the human mind. Research at one level provides constraints, correlations and inspirations for research at another level.

Neuroanatomy Basics[değiştir]

The basic building blocks of the brain are a special sort of cells called neurons. There are approximately 100 billion neurons involved in information processing in the brain. When we look at the brain superficially, we can't see these neurons, but rather look at two halves called the hemispheres. The hemispheres themselves may differ in size and function, as we will see later in the book, but principally each of them can be subdivided into four parts called the lobes: the temporal, parietal, occipital and frontal lobe. This division of modern neuroscience is supported by the up- and down-bulging structure of the brain's surface. The bulges are called gyri (singular gyrus), the creases sulci (singular sulcus). They are also involved in information processing. The different tasks performed by different subdivisions of the brain as attention, memory and language cannot be viewed as separated from each other, nevertheless some parts play a key role in a specific task. For example the parietal lobe has been shown to be responsible for orientation in space and the relation you have to it, the occipital lobe is mainly responsible for visual perception and imagination etc. Summed up, brain anatomy poses some basic constraints to what is possible for us and a better understanding will help us to find better therapies for cognitive deficits as well as guide research for cognitive psychologists. It is one goal of our book to present the complex interactions between the different levels on which the brain that can be described, and their implications for Cognitive Neuropsychology.

Methods[değiştir]

Newer methods, like EEG and fMRI etc. allow researchers to correlate the behaviour of a participant in an experiment with the brain activity which is measured simultaneously. It is possible to record neurophysiological responses to certain stimuli or to find out which brain areas are involved in the execution of certain mental tasks. EEG measures the electric potentials along the skull through electrodes that are attached to a cap. While its spatial resolution is not very precise, the temporal resolution lies within the range of milliseconds. The use of fMRI benefits from the fact the increased brain activity goes along with increased blood flow in the active region. The haemoglobin in the blood has magnetic properties that are registered by the fMRI scanner. The spatial resolution of fMRI is very precise in comparison to EEG. On the other hand, the temporal resolution is in the range of just 1–2 seconds.

Conclusion[değiştir]

Remember the scenario described at the beginning of the chapter. Knut was asking himself “What is happening here?” It should have become clear that this question cannot be simply answered with one or two sentences. We have seen that the field of Cognitive Psychology comprises a lot of processes and phenomena of which every single one is subject to extensive research to understand how cognitive abilities are produced by our brain. In the following chapters of this WikiBook you will see how the different areas of research in Cognitive Psychology are trying to solve the initial question raised by Knut.