O V E R V I E W 87
4.1 Cognitive science: An interdisciplinary endeavor 88
4.2 Levels of explanation: The contrast between psychology and
neuroscience 91
How psychology is organized 91 How neuroscience is organized 93 4.3 The integration challenge 95
How the fields and sub-fields vary 96 The space of cognitive science 97
4.4 Local integration I: Evolutionary psychology and the psychology of reasoning 99
Conditional reasoning 100 The reasoning behind
cooperation and cheating: The prisoner’s dilemma 102 4.5 Local integration II: Neural
activity and the BOLD signal 105
Overview
Cognitive science draws upon the tools and techniques of many different disciplines. It is a fundamentally interdisciplinary activity. As we saw in our tour of highlights from the history of cognitive science inChapters 1through3, cognitive science draws on insights and methods from psychology, linguistics, computer science, neuroscience, mathematical logic. . . The list goes on. This basic fact raises some very important and fundamental questions. What do all these disciplines have in common? How can they all come together to form a distinctive area of inquiry? These are the questions that we will tackle in this chapter and the next.
The chapter begins insection 4.1with a famous picture of how cognitive science is built up from six constituent disciplines. Whatever its merits as a picture of the state of the art of cognitive science in the 1970s, the Sloan hexagon is not very applicable to contemporary cognitive science. Our aim will be to work towards an alternative way of thinking about cognitive science as a unified field of investigation.
The starting-point for the chapter is that the different disciplines in cognitive science operate at different levels of analysis and explanation, with each exploring different levels of organization in the mind and the nervous system. The basic idea of different levels of explanation and organization is introduced insection 4.2. We will look at how the brain can be studied at many different levels, from the level of the molecule upwards. There are often specific disciplines or sub-disciplines corresponding to these different levels – disciplines with their own specific tools and technologies.
The basic challenge this poses is explaining how all these different levels of explanation fit together. This is what insection 4.3I term the integration challenge. As we will see, the integration challenge arises because the field of cognitive science has three dimensions of variation. It varies according to the aspect of cognition being studied. It varies according to the level of organization at which that aspect is being studied. And it varies according to the degree of resolution of the techniques that are being used.
There are two different strategies for responding to the integration challenge. There are global strategies and local strategies. Global strategies look for overarching models that will explain how cognitive science as a whole fits together. Marr’s tri-level model of explanation (discussed in
section 2.3) is a good example. We will look at global strategies inChapter 5. This chapter, in contrast, paves the way by looking at examples of local integrations across levels of organization and levels of explanation. These are cases where cognitive scientists have built bridges between different levels of explanation and different levels of organization.
Our first example of a local integration comes from disciplines that are relatively high-level. Insection 4.4we will look at the proposal from evolutionary biologists to integrate evolutionary biology with psychological studies of reasoning. The second local integration, covered insection 4.5, is located at the opposite end of the spectrum. It is the integration of studies of blood oxygen levels (as measured by functional neuroimaging technologies) with studies of the activity of populations of neurons.
4.1
Cognitive science: An interdisciplinary endeavor
The hexagonal diagram in Figure 4.1 is one of the most famous images in cognitive science. It comes from the 1978 report on the state of the art in cognitive science commissioned by the Sloan Foundation and written by a number of leading scholars, including George Miller (whom we encountered inChapter 1). The diagram is intended to illustrate the interdisciplinary nature of cognitive science. The lines on the diagram indicate the academic disciplines that the authors saw as integral parts of cognitive science, together with the connections between disciplines particularly relevant to the study of mind and cognition.
Each of the six disciplines brings with it different techniques, tools, and frameworks for thinking about the mind. Each of them studies the mind from different perspec- tives and at different levels. Whereas linguists, for example, develop abstract models of linguistic competence (the abstract structure of language), psychologists of language are interested in the mechanisms that make possible the performance of language users.
Whereas neuroscientists study the details of how the brain works, computer scientists abstract away from those details to explore computer models and simula- tions of human cognitive abilities. Anthropologists are interested in the social dimen- sions of cognition, as well as how cognition varies across cultures. Philosophers, in contrast, are typically interested in very abstract models of how the mind is realized by the brain.
Faced with these obvious differences between the six disciplines occupying the individual nodes of the hexagon, it is natural to wonder whether there is anything bringing them together besides a shared interest in the study of the mind and cognition. The authors of the Sloan report certainly thought that there was. The diagram is intended to convey that there is far more to the collective and collabora- tive nature of cognitive science than simply an overlap of interest and subject matter. Cognitive science, according to the report, is built on partnerships and connections. Lines on the diagram indicate where the authors saw interdisciplinary connections.
Some of the connections identified in the diagram were judged stronger than others. These are marked with a solid line. The weaker connections are marked with a broken
Philosophy Linguistics Anthropology Neuroscience Artificial Intelligence Psychology
Key: Unbroken lines = strong interdisciplinary ties
Broken lines = weak interdisciplinary ties
Figure 4.1 Connections among the cognitive sciences, as depicted in the Sloan Foundation’s 1978 report. Unbroken lines indicate strong interdisciplinary links, while broken lines indicate weaker links. (Adapted from Gardner1985)
line. In a retrospective memoir published in 2003, Miller explained some of the connec- tions represented in the figure:
Thus, cybernetics used concepts developed by computer science to model brain func- tions elucidated in neuroscience. Similarly, computer science and linguistics were already linked through computational linguistics. Linguistics and psychology are linked by psycholinguistics, anthropology and neuroscience were linked by studies of the evolution of the brain, and so on. Today, I believe, allfifteen possible links could be instantiated with respectable research, and the eleven links we saw as existing in 1978 have been greatly strengthened. (Miller2003: 143)
At least one of the connections that was judged weak in 1978 has now become a thriving sub-discipline of philosophy. A group of philosophers impressed by the potential for fruitful dialog between philosophy and neuroscience have taken to calling themselves neurophilosophers, after the title of a very influential book by Patricia Churchland (1986).
Exercise 4.1 Can you think of other illustrations of the lines that the Sloan report draws between different disciplines?
Miller’s own account of how the Sloan report was written is both disarming and telling. “The committee met once, in Kansas City. It quickly became apparent that everyone knew his own field and had heard of two or three interesting findings in other fields. After hours of discussion, experts in discipline X grew unwilling to make any judgments about discipline Y, and so forth. In the end, they did what they were compe- tent to do: each summarized his or her own field and the editors – Samuel Jay Keyser, Edward Walker and myself– patched together a report” (Miller2003: 143). This may be how reports get written, but it is not a very good model for an interdisciplinary enter- prise such as cognitive science.
In fact, the hexagon as a whole is not a very good model for cognitive science. Even if we take seriously the lines that mark connections between the disciplines of cognitive science, the hexagon gives no sense of a unified intellectual enterprise. It gives no sense, that is, of something that is more than a composite of “traditional” disciplines such as philosophy and psychology. There are many different schools of philosophy and many different specializations within psychology, but there are certain things that bind together philosophers as a group and psychologists as a group, irrespective of their school and specialization. For philosophers (particularly in the so-called analytic tradition, the tradition most relevant to cognitive science), the unity of their discipline comes from certain problems that are standardly accepted as philosophical, together with a commitment to rigorous argument and analysis. The unity of psychology comes, in contrast, from a shared set of experimental tech- niques and paradigms. Is there anything that can provide a similar unity for cognitive science?
4.2
Levels of explanation: The contrast between psychology
and neuroscience
Neuroscience occupies one pole of the Sloan report’s hexagonal figure and it was not viewed as very central to cognitive science by the authors of the report. The report was written, after all, before the “turn to the brain” described in Chapter 3, and its focus reflected the contemporary focus on computer science, psychology, and linguis- tics as the core disciplines of cognitive science. Moreover, the authors of the report treated neuroscience as a unitary discipline, on a par with anthropology, psychology, and other more traditional academic disciplines. The explosion of research into what became known as cognitive neuroscience has since corrected both of these assump- tions. Most cognitive scientists place the study of the brain firmly at the heart of cognitive science. And it is becoming very clear that neuroscience is itself a massively interdisciplinary field.