Psychology 3130A/B Chapter Notes - Chapter 6: Conjunction Fallacy, Catfield, First Statement
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20 Dec 2017
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Chapter 6: Inference and Induction
- Induction is about predicting the future
Role of Induction in thinking
Inferences and conclusions
• Use induction to make inferences
• Inferences are conclusions based on available evidence
Generalization
• Induction is also used when we make generalization
• Generalization is also an inductive conclusion, but rather than describing a specific prediction,
generalization is a broad conclusion about a whole class or group of things
• Rely on it to make inferences about how people will behave and react
• Rely on inductive reasoning to discover something new by thinking
How induction works
Hue’s prole of idutio
• David Hume considered induction to be one of the greatest problems
o Unlike deductive logic, which many believed could be explained by formal operations, induction
seemed to defy this
• Hume gave a description of what he called the problem of induction
o Induction = act of relying on past experience to make inferences and conclusions about future
o Thought this was circular reasoning
• b/c it works if the future resembles the past; but Hume claimed that this only works because the future
reseles the past …i the past
• problem with this is we cant use these past inductive successes to predict future inductive successes
• relying on induction to explain induction
• says we rely on induction because we have a habit, but instead would argue that our cognitive system
is designed to track regularities in the world, and make conclusions and predictions on basis for those
regularities
Basic Learning mechanisms
• all cognitive systems rely on the fundamental processes of associative learning
• a relate it to lassial oditioig; ted to talk aout oditioed respose, also fair to sa it’s a
simple inductive inference (make prediction, generate explanation)
Stimulus generalization
• conceptual advantage of relating induction to basic learning theory is that we can also talk about the
role of similarity and stimulus generalization
• can also relate it to operant conditioning; rat makes inferences about presentation of food following
various lights
• universal law of stimulus generalization generalization gradient
o Rat pressing level when its red (been reinforced) but also when it was similar shade of red
• Something fundamental and universal about generalizing the new stimuli as a function of how similar
they are to previously experienced stimuli
• Tendency to base predictions about future on similarity to past events should also obey this universal
law of stimulus generalization
Gooda’s prole of idutio
• According to Hume, induction may be a habit, but its difficult to explain in logical terms without
resorting to some kind of circular argument
• Nelson Goodman raised similar concern
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• His eaple: iagie ou are a eerald eaier, eer oe ou’e see so far is gree
o So we can say all emeralds are green; this is saying all we have seen are green and any we will
see will be green
• This inductive inference is made with confidence
• But there is a prole, osider alteratie propert alled grue
• If you say, all emeralds are grue, it means that all the emeralds that you have seen so far are green and
all emeralds that have not yet been seen are blue: green emeralds in the past, but blue emeralds from
this moment forward
• Goodmans point, is that at any given time this property of grue is true
• Both properties are true given the evidence of green emeralds
• Notice, past experience (green emeralds) is identical for both properties
• His suggestion is that both of these properties green and grue, can be simultaneously true, given
available evidence
• Possible all emeralds are green, also possible some are blue, but you have not seen them yet
o These properties also make opposite prediction about what colour the next emerald will be
• If green is true, then next emerald will be green; if grue is true then next will be blue
• Since both are true, clear prediction cant be made; and yet we will all predict the next emerald will be
green; why? This is a problem of induction
Entrenchment and natural kinds
• Hume stated we have a habit to make inductions; current understanding of learning theory suggests
that we naturally generalize
• Gooda’s is’t as straight forard, ho do e hoose hih oe of the idutios to ake
• Entrenchment = term or property has a history of usage w/in a culture or language
• Emerald example: green is an entrenchment term (term we can use to describe many things)
• Grue however is not an entrenchment; no history of usage and no general property of grue outside the
emeralds that were grue yesterday and blue tomorrow
o Goodman argued we can only make reliable inductions from entrenchment terms
o
• Quine argued that natural kinds are natural groupings of entities that possess similar properties,
much like what we have referred to earlier as a family resemblance concept
o Suggested that objects form a kind only if they have apple properties that can be projected to
all the members (e.g. apple is natural grouping; not apple is not)
o Argued all humans make use of natural kinds; reliable inductions come from natural kinds
• Quie’s otio of a atural kid suggests a solutio for Nelso Gooda’s prole of idutio
• Quine pointed out that green is a natural property
• Green emeralds form a kind via similarity; grue emeralds do not
Categorical induction
• Most organisms have a tendency to display stimulus generalization
• Basic generalization is sensitive to the similarity b/w the current stimulus and mental representations
of previously experienced stimuli
• Have shown in other chapters that concepts and categories are often held together by similarity
• Productive way to investigate inductive reasoning is to consider that inductions are often based on
concepts and categories
o Known as literature as categorical induction
Structure of an induction task
• For the present purposes, we can define categorical induction as the process of which people arrive at
a conclusion or a statement of confidence about whether a conclusion category has some given
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