Download Selection and Change

Selection and Change:
Biology and Behavior
AILUN – Lecture 4
S. Glenn - AILUN 2008
Process and Content in Scientific Explanation
• Content in Science
– The phenomena of interest (e.g. movements of heavenly bodies,
composition of matter, differences in species, child’s head-banging)
– That which the scientific method is used to understand and explain
– Begins with everyday observation but often ends with terms derived
from identifying process
• Process in Science
– Mechanisms or forces that explain observed phenomena (natural
selection, reinforcement, gravity)
– Usually describe functional relations among classes
– Virtually always entails a different way of classifying (e.g. operants) as
natural lines of fracture are identified
– Early description of processes often lead to new concepts (e.g. genes)
S. Glenn - AILUN 2008
Examples of Process and Content in
Biology and Learned Behavior
Selection
Process
Domain
Content (Results of
Selection Process)
Natural
selection
Living
things
E. coli
D. melanogaster
Operant
selection
Learned
behavior
Rat #1’s leverpressing
Ricardo’s cake baking
S. Glenn - AILUN 2008
Variation among Organisms of a Biological Population
(Species) in a Specific Environment
Time 1
Time 2
Time 3
Time 4
• Individual organisms of a moth species vary in features (color/size)
• Successive populations exist in an unchanging environment in which all
features are equally adapted
• The contingent relation between the moths and their environment
is stable and the population is in a relatively steady state
S. Glenn - AILUN 2008
Change in Selection Contingencies
Time 1
Time 2
Time 3
Time 4
• Environment gradually changes
• Contingencies of survival increasingly favor darker moths
• Lineage that began with mostly white moths at Time 1 has
mostly black moths at Time 4
S. Glenn - AILUN 2008
Some Results of Natural Selection1
• Changes over time in properties of organisms of a species
– Successive populations become on average larger, smaller, darker,
lighter, etc.
• Speciation or splitting of lineages into daughter species with
different evolutionary trajectories
– Common ancestor species of humans and bonobo chimps has
descendants of different species
• Organisms in some lineages become structurally more complex
– Single cell -> multiple cells
– Differentiation of cellular functions
– Organs and their functional interrelations
• Organisms in some lineages become functionally more complex
– More parts of the physical environment affect survival/reproduction
– More parts of the organism are involved in behavior
– Behavior has more effects on the environment
• Relations among natural populations (ecologies) become
increasingly complex
S. Glenn - AILUN 2008
Variants of an Operant Population in a Specific
Environment
VI-4 min
• Individual keypecks of a pigeon vary in many features,
including IRT lengths
• These pecks occur in an environment where pecking
produces food on a VI 4 min schedule
• Is there a relation between IRT lengths and the contingency?
S. Glenn - AILUN 2008
Selection in an Operant Population
VI-4 min
•
•
-----------------FR 30-----------------------------------------
Change the selection contingency so that reinforcement
is on FR-30 schedule and the population evolves
IRTs becoming increasingly concentrated at .7 “ and .4”
over 50 min after abrupt change in selecting
environment
2 Figure from Blough, 1963
S. Glenn - AILUN 2008
Some Results of Operant Selection
• Changes over time in properties of responses
in an operant lineage
– Ex: IRTs become much shorter
• Origin of new operants in a repertoire
– Ex: Shaping of leverpress
• Increasing complexity of behavioral
occurrences
– Ex: Baking a cake becomes a functional unit
• Increasing numbers of stimulus control
relations
– Ex: Distinction between Uncle B and Uncle S
– Ex: Distinction between species of spider
S. Glenn - AILUN 2008
The Effect of Operant Selection
on Complexity of Learned Behavior
• The behavioral instances of a lineage become more
complex in organization as lineages split and evolve
– Single component responses -> chains and modular units
– Response differentiation and diverging lineages
– Modular units become functionally interrelated
• Operants relate to environment in more ways
– More parts of the physical environment become controlling
variables (discrimination, generalization, conditional control, etc.)
– More parts of the organism are involved in behavior
– Behavior causes increasingly greater changes in the environment
• Result is a web of interrelations among behavioral
units in an individual repertoire
S. Glenn - AILUN 2008
Toward A General Account
•
•
•
•
Selection may account for change in multiple domains and each domain is
distinguished by the locus of its content
– Biological evolution is gene-based and its lineages (species) are
localized in biospheres
– Operant learning is neuron-based and lineages (operants) are localized
within individual organisms
– Cultural evolution is operant-based and lineages are localized in social
groups of behaviorally-related organisms
Selectionist theory in each domain is built on the concepts particular to
that domain
A general account moves the scientific language of specific domains to a
meta-language that can apply to multiple domains
Process terms of a general account must apply to all levels of organization
S. Glenn - AILUN 2008
Class Terms Suggested by David Hull
for A General Account of Selection
Natural Kinds
Interactors
Replicators
Lineages
Function
Effect
Interact
differentially with
environment
Pass traits to next
generation
Differential replication
Retain effects on
population of
previous selection
cycles
Evolution (change over
time in characteristics
of a natural population)
S. Glenn - AILUN 2008
Change in trait
frequencies of lineage
A General (Content Free) Account of
Selection3
• A ‘natural population’ of entities exists in space/time
• Entities in the population must have a common origin (are
related by ‘descent’)
• Entities constituting the population must vary in ‘inherited’
traits or characteristics
• Differential interactions of entities with their
environment causes differential replication of some
traits over others (selection)
• Differential replication results in change in frequency
of inherited traits in the natural population
• Locus of evolution is in the changing natural
populations that constitute a lineage
S. Glenn - AILUN 2008
Summary
• Content of a scientific domain is what is to be
explained
• Processes are described that designed to explain
the content
• Selection is explanatory concept in biological
evolution and operant learning
• A general account of selection will use class
terms that subsume concepts in all domains to
which the account applies
S. Glenn - AILUN 2008
References
1
2
3
Mayr, E. (1982). The growth of biological thought. Cambridge, MA:
Harvard University Press.
Blough, D. S. (1963). Interresponse time as a function of continuous
variables: A new method and some data. Journal of the Experimental
Analysis of Behavior, 6, 237-246.
Hull, D. L., Langman, R. E. & Glenn, S. S. (2001). A general account of
selection: Biology, immunology and behavior. Behavioral and Brain
Sciences, 24, 511-528.