From Causation to From Causation to Mechanisms Mechanisms Review Review Experiments provide the best evidence of a causal Experiments provide the best evidence of a causal relation, but sometimes they are not possible relation, but sometimes they are not possible Since it is impossible physically or morally to Since it is impossible physically or morally to manipulate the independent variable manipulate the independent variable Two strategies Two strategies Prospective studies Prospective studies Divide groups according to the independent Divide groups according to the independent variable and investigate correlation with the variable and investigate correlation with the dependent variable dependent variable Retrospective studies Retrospective studies Divide group according to the dependent variable Divide group according to the dependent variable and investigate correlation with the independent and investigate correlation with the independent variable variable Two limitations of causes for Two limitations of causes for science science Individual causal relations do not accomplish much Individual causal relations do not accomplish much It requires a coordinated system of causes to get It requires a coordinated system of causes to get something done something done What relates causes to their effects? What relates causes to their effects? Typically there are processes intervening between Typically there are processes intervening between causes and their effects causes and their effects Between and within causal relations scientists look for Between and within causal relations scientists look for mechanisms mechanisms Parts (entities) and operations (activities) Parts (entities) and operations (activities) organized to produce an phenomenon organized to produce an phenomenon
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From Causation to From Causation to MechanismsMechanisms
ReviewReviewExperiments provide the best evidence of a causal Experiments provide the best evidence of a causal relation, but sometimes they are not possible relation, but sometimes they are not possible
Since it is impossible physically or morally to Since it is impossible physically or morally to manipulate the independent variablemanipulate the independent variable
Two strategiesTwo strategiesProspective studiesProspective studies
Divide groups according to the independent Divide groups according to the independent variable and investigate correlation with the variable and investigate correlation with the dependent variabledependent variable
Retrospective studiesRetrospective studiesDivide group according to the dependent variable Divide group according to the dependent variable and investigate correlation with the independent and investigate correlation with the independent variablevariable
Two limitations of causes for Two limitations of causes for sciencescience
Individual causal relations do not accomplish muchIndividual causal relations do not accomplish muchIt requires a coordinated system of causes to get It requires a coordinated system of causes to get something donesomething done
What relates causes to their effects?What relates causes to their effects?Typically there are processes intervening between Typically there are processes intervening between causes and their effectscauses and their effects
Between and within causal relations scientists look for Between and within causal relations scientists look for mechanismsmechanismsParts (entities) and operations (activities) Parts (entities) and operations (activities) organized to produce an phenomenonorganized to produce an phenomenon
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The Ubiquity of Mechanisms in The Ubiquity of Mechanisms in ScienceScience
Mechanisms in physical sciencesMechanisms in physical sciencesSolar system mechanicsSolar system mechanicsMechanisms of chemical reactionsMechanisms of chemical reactions
Mechanisms in biological sciencesMechanisms in biological sciencesMechanisms of photosynthesisMechanisms of photosynthesisMechanisms of reproductionMechanisms of reproduction
Mechanisms in behavioral sciencesMechanisms in behavioral sciencesMechanisms of memory encodingMechanisms of memory encodingMechanisms of decision makingMechanisms of decision making
Mechanisms in social sciencesMechanisms in social sciencesMechanisms of consensus formationMechanisms of consensus formation
Mechanisms as Coordinated Mechanisms as Coordinated CausationCausation
Mechanisms are made of parts Mechanisms are made of parts causingcausing changes in changes in other parts, enabling mechanisms to other parts, enabling mechanisms to causecause changes in changes in yet other thingsyet other thingsMuscles in heart contract while Muscles in heart contract while valves open and shut, valves open and shut, enablingenabling
The heart to move blood The heart to move blood through arteries and veinsthrough arteries and veins
Understanding a mechanismUnderstanding a mechanismrequires experimental requires experimental procedures designed to figure out the parts, their causal procedures designed to figure out the parts, their causal operation, and how these operations are coordinated so operation, and how these operations are coordinated so that the mechanism can produce its effectthat the mechanism can produce its effect
Designing Mechanisms Designing Mechanisms vsvsDiscovering MechanismsDiscovering Mechanisms
The challenge in engineering is to design new The challenge in engineering is to design new mechanisms that produce the phenomena we are mechanisms that produce the phenomena we are interested ininterested in
Typically, engineers begin with an objective and Typically, engineers begin with an objective and recruit parts already known to perform operationsrecruit parts already known to perform operationsTheir challenge is to discover new modes of Their challenge is to discover new modes of organization that enable the parts to together do organization that enable the parts to together do somehtingsomehting newnew
Scientists do not have access to the design manuals of Scientists do not have access to the design manuals of the mechanisms operative in the natural worldthe mechanisms operative in the natural world
They must They must reverse engineerreverse engineer themthem——discover the discover the parts, the operations, and the organizationparts, the operations, and the organization
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Early machines: Variations on a Early machines: Variations on a themetheme
WedgeWedge
RampRamp
Screw
Early simple machines used human energy but extended its capacity
• In these cases, shape and spatial layout explain the causal efficacy
Early machines: Variations on Early machines: Variations on another themeanother theme
LeverLever
WheelWheel
PulleyPulley
In these cases, shape and layout together with coordination of parts explains the effect
Simple mechanisms as tools to Simple mechanisms as tools to make tasks easiermake tasks easier
Permit the performance of activities that otherwise would not be possible
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Combining simple mechanismsCombining simple mechanisms
Engineering: organizing Engineering: organizing components to produce components to produce effectseffects
Common force for creating new Common force for creating new machines: warfaremachines: warfare
The Gastrophetes or belly bow, introduced around 400 BCE, designed to launch arrows further and more accurately than the traditional bow
The Oxybeles, introduced around 375 BCE, provided ever greater power and accuracy
Common force for creating new Common force for creating new machines: warfaremachines: warfare
Ballista, introduced around 50 BCE, used more for throwing stones than arrows
Onager, developed around 350 CE, was a low cost way of launching projectiles such as clay balls with Greek fire inside
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Common force for creating new Common force for creating new machines: warfaremachines: warfare
Trebuchet: a counterweighted catapult designed to throw heavy projectiles
Such as pianos!• Chris throwing Maggie’s piano in
Northern Exposure
From Simple to ComplexFrom Simple to ComplexCommon theme in both engineering and scienceCommon theme in both engineering and science
Begin with simple designs but increasingly engineer Begin with simple designs but increasingly engineer or discover more and more complex mechanismsor discover more and more complex mechanismsLarge numbers of partsLarge numbers of partsPerforming many different operationsPerforming many different operationsCoordinated in ever more complex waysCoordinated in ever more complex ways
Nature as a machine:Nature as a machine:Rene DescartesRene Descartes
“I have described this earth and indeed the whole universe as if it were a machine: I have considered only the various shapes and movements of its parts” (Principia IV 188).
All action in the physical universe due to shape and motion of physical matter
No vacuumNo action at a distance
Magnetism: Screw-shaped particles (formed in vortices) fit into threads in iron.
“I have described this earth and indeed the whole universe as if it were a machine: I have considered only the various shapes and movements of its parts” (Principia IV 188).
All action in the physical universe due to shape and motion of physical matter
No vacuumNo action at a distance
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Robert Boyle: Restorer of the Robert Boyle: Restorer of the Mechanical PhilosophyMechanical Philosophy
Introduced the name mechanical philosophy.
Air pump—adapted design of Otto von Guericke
Air molecules as springs
Boyle’s law: “the hypothesis, that supposes the pressures and expansions to be in reciprocal proportion”
Descartes: Animals Descartes: Animals as machinesas machines
Impressed by the statuary in the Royal Gardens that moved by hydraulic principles
Animal bodies are purely mechanical devices
Circulation of blood due to heating in the heart, causing the expansion of droplets of blood, which then forced their way through the arteries
Nerve transmission and brain activity purely mechanical (albeit influenced by the mind in humans)
Humans as machinesHumans as machinesDescartes could not conceive of a mechanism that could think or use language
• Accordingly, held that the human capacity for thought was not due to a mechanism
• Rather, thought due to a non-material mind
Julien Offray de La Mettrie objected that Descartes did not go far enough—all human activities, including thinking explained in mechanical terms
• Man the Machine in 1748
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Newton: Expanding the Newton: Expanding the mechanical philosophymechanical philosophy
Endorsed the mechanical philosophyLight and heat nothing but particles in motion
“I wish we could derive the rest of the phenomena of Nature by the same kind reasoning from mechanical principles, for I am induced by many reasons to suspect that they may all depend upon certain forces by which the particles of bodies, by some causes hitherto unknown, are each mutually impelled towards one another, and cohere in regular figures, or are repelled and recede from one another. These forces being unknown, philosophers have hitherto attempted the search of Nature in vain; but I hope the principles here laid down will afford some light either to this or some truer method of philosophy”
Preface to Principia
Jacques de Jacques de VaucansonVaucanson (1709(1709--1782):1782):“Moving Anatomy”“Moving Anatomy”
Mechanical duck Mechanical duck could move in the typical, wagging way of could move in the typical, wagging way of
a ducka duckeat and digest fisheat and digest fishexcrete the remains in a "natural" way excrete the remains in a "natural" way
Mechanism was driven by a weightMechanism was driven by a weight
Consisted of more than a thousand moving Consisted of more than a thousand moving parts, concealed inside the duck and the parts, concealed inside the duck and the base on which the bird stood base on which the bird stood
Besides the duck, a flute and tambourine Besides the duck, a flute and tambourine playerplayer
Applying mechanical ideas to living Applying mechanical ideas to living organismsorganisms
Living things seem to behave in complex Living things seem to behave in complex ways that defy simple mechanical ways that defy simple mechanical explanationexplanation
Vitalists maintained that the complexity Vitalists maintained that the complexity and and purposivenesspurposiveness of biological of biological processes made mechanical explanation processes made mechanical explanation impossibleimpossible
Mechanists developed more complex Mechanists developed more complex conceptions of mechanismsconceptions of mechanisms
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TropismTropismTwo principles of Jacques Loeb:Two principles of Jacques Loeb:(i) The movements of an organism to or from a center of a (i) The movements of an organism to or from a center of a stimulus are caused by action of the stimulus on the stimulus are caused by action of the stimulus on the receptors, and through these on the organs of locomotion, receptors, and through these on the organs of locomotion, in consequence of which the animal turns until its body is in consequence of which the animal turns until its body is symmetrically stimulated and an equilibrium obtained symmetrically stimulated and an equilibrium obtained between the two sides. between the two sides. (ii) These movements occur mechanically, as a result of (ii) These movements occur mechanically, as a result of physical and chemical changes in the receptors and physical and chemical changes in the receptors and effectors, with no real effort on the part of the organism. effectors, with no real effort on the part of the organism.
Designing a Designing a tropistictropistic machinemachine
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Designing a Designing a tropistictropistic machinemachine
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Characterizing mechanismsCharacterizing mechanismsParts (entities) and operations (activities) Parts (entities) and operations (activities) organized to produce an phenomenonorganized to produce an phenomenon
Start with a phenomenon of interest:Start with a phenomenon of interest:tropism of plantstropism of plantscell divisioncell divisionremembering events in one’s liferemembering events in one’s lifeincreasing worker productivityincreasing worker productivity
Describing the PhenomenonDescribing the PhenomenonBefore setting out to explain a phenomenon, need to Before setting out to explain a phenomenon, need to characterize it as accurately as possiblecharacterize it as accurately as possible
Otherwise one risks trying to explain something that Otherwise one risks trying to explain something that might not be possiblemight not be possible
An important role for purely An important role for purely observational researchobservational researchBefore seeking a mechanism by which the universe Before seeking a mechanism by which the universe continues to expand, make sure it iscontinues to expand, make sure it isBefore explaining mechanism of global warming, Before explaining mechanism of global warming, make sure it is really occurringmake sure it is really occurring
But the description of the phenomena may be But the description of the phenomena may be revisedrevisedin the process of figuring out the mechanismin the process of figuring out the mechanism
Mechanisms have Mechanisms have working working partsparts
To understand a mechanism, one must To understand a mechanism, one must decomposedecompose itit——take it aparttake it apart
LiterallyLiterally——actually remove the parts to study them in actually remove the parts to study them in isolationisolationFigurativelyFiguratively——figure out what the parts are and what figure out what the parts are and what they do they do
In identifying components, focus both on theirIn identifying components, focus both on theirStructureStructureFunction Function
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Structural components of cellsStructural components of cellsCell components tend to have boundaries (membranes) that restrict access
Components have istinctiveappearances, especially when stained Worry—since things have to be manipulated to be seen, is what you see reflective of what is there?
Or is it a product of your manipulation: an artifact
What are the parts of the brain?What are the parts of the brain?Open up the skull, and you see Open up the skull, and you see a hunk of grey matter highly a hunk of grey matter highly convolutedconvoluted
What are the What are the workingworking parts of parts of the brain?the brain?
Sulci and Gyri?
Lobes?
What are the working parts of the What are the working parts of the brain?brain?
Korbinian Brodmann (1909) assumed differences in neuron Korbinian Brodmann (1909) assumed differences in neuron type, density, layering, probably related to functiontype, density, layering, probably related to function
Delineated areas in the brains of humans and many other species
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What are the working parts of the What are the working parts of the brain?brain?
With improved tools, including tools for tracing the With improved tools, including tools for tracing the connectivity of neural processes (axons and dendrites) connectivity of neural processes (axons and dendrites) modern brain modern brain mappersmappers have developed maps that seem to have developed maps that seem to correspond to functioncorrespond to function
What operations do the What operations do the components perform?components perform?
Just locating and isolating a component doesn’t reveal Just locating and isolating a component doesn’t reveal what the component doeswhat the component does
How does one figure out what these things do?
Sometimes probing a item in various ways will reveal what it does
What operations do the What operations do the components perform?components perform?
Often one must reason backwards from what the whole Often one must reason backwards from what the whole mechanism does to what operations are needed to perform mechanism does to what operations are needed to perform that activitythat activity
Often these operations are not obviousOften these operations are not obviousReverse engineeringReverse engineeringFiguring out what task needs to be performedFiguring out what task needs to be performedUsing information about the type of operations that Using information about the type of operations that have been previously identified in similar systemshave been previously identified in similar systemsDrawing Drawing uponupon analogies with machines made by analogies with machines made by humanshumans
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What are the operations in What are the operations in fermentation?fermentation?
Strategies of discovering Strategies of discovering intermediate operationsintermediate operations
Isolate possible intermediariesIsolate possible intermediariesInhibit possible intermediate processes to see if Inhibit possible intermediate processes to see if that stops the reactionthat stops the reaction——lesion experimentlesion experimentInsert possible intermediaries to see if they Insert possible intermediaries to see if they could produce the end productcould produce the end product——excitation excitation experimentexperiment
pq
r stuv w
Inhibition (lesion)
Excitation Detection
OrganizationOrganizationThe third feature of mechanisms is that they are organized The third feature of mechanisms is that they are organized and that the organization mattersand that the organization matters
Grains of sand in a sand pile are notGrains of sand in a sand pile are notorganized: you can recombine theorganized: you can recombine thegrains at will and nothing happensgrains at will and nothing happens
In mechanisms, one part depends on others, so organization In mechanisms, one part depends on others, so organization mattersmatters
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Exemplary mechanism: the Exemplary mechanism: the computercomputer
In the midIn the mid--1919thth century Charles Babbage had the idea to century Charles Babbage had the idea to mechanize computationmechanize computation
The Difference Engine
The Analytical Engine
Creating programs: Creating programs: AdaAda Byron, Byron, Countess of LovelaceCountess of Lovelace
Her mother had her trained in Her mother had her trained in mathematics so she wouldn’t be mathematics so she wouldn’t be tempted to be a poet like her fathertempted to be a poet like her father
Became friends with Babbage and Became friends with Babbage and helped sell his analytical engine to helped sell his analytical engine to Italian sponsorsItalian sponsors
Recognized the promise of a general Recognized the promise of a general computer: "developing and tabulating computer: "developing and tabulating any function whatever. . . the engine any function whatever. . . the engine [is] the material expression of any [is] the material expression of any indefinite function of any degree of indefinite function of any degree of generality and complexity." generality and complexity."
Mechanizing computingMechanizing computing
111
00
0 0 1 11
0
0
1
a0 --> 1Laa1 --> 1Lcb0 --> 0Rab1 --> 1Rd
c0 --> Halt
z1 --> 0Rs
:.
Sequences of simple mechanical operations could compute any given function
A special version of such a machine could compute all computable functions: Universal Turing Machine
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Actual computers: Actual computers: Army, Census Army, Census Bureau, and Bureau, and
Predicting ElectionsPredicting Elections
The question reversesThe question reversesComputers became tools for modeling mental activities: Computers became tools for modeling mental activities: designing computers to simulatedesigning computers to simulate
PerceivingPerceivingRememberingRememberingUsing languageUsing language
Do computers think?Do computers think?Remember, they were built upon the model of how the Remember, they were built upon the model of how the human mind was thought to work!human mind was thought to work!
Do humans think by carrying out the same operations in Do humans think by carrying out the same operations in the same way as computers?the same way as computers?
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