Implicit learning Zoltán Dienes Conscious and unconscious mental processes

Implicit learning People learn to make decisions on a task more accurately or more quickly without being able to justify their decisions adequately. OR: The learning process by which people come to acquire implicit (unconscious) knowledge. Consider: Acquisition of natural language, social skills, musical appreciation, many practical skills

Outline: 1.Basic experimental paradigms for investigating implicit learning (3 paradigms) 2.Ways of telling whether knowledge is unconscious (3 methods) 3.What properties does unconscious knowledge have? (2 properties)

Three common paradigms for investigating implicit learning: 1.Artificial grammar learning 2.Dynamic control tasks (complex systems) 3.Serial reaction time (SRT) task

Dynamic control tasks: Subjects interact with a simulated system, e.g. the sugar production factory (Berry & Broadbent 1984) On each trial, hire and fire workers to try to maintain the level of sugar production at a target value. Underlying equation (unknown to subjects) links current sugar production to number of workers and past sugar production. Donald Broadbent

Other dynamic control tasks include: Interacting with a person, trying to make them friendly Controlling a traffic system Berry and Broadbent (1984) Training on the task improved ability to control the system but not ability to answer questions about how the system worked Trying to consciously work out the rules impairs learning

Serial reaction time task (Nissen & Bullemer, 1987) On each trial a light goes on Just press corresponding button Unbeknownst to subject, sequence of lights is rule governed

Rule governed Violates rules Subjects are sensitive to the presence of the sequence even when they deny knowing that there was a sequence

To investigate implicit learning First need to have a method for determining when knowledge is conscious and when unconscious Then can investigate the properties of unconscious knowledge and how it might differ from conscious knowledge in terms of: The conditions under which learning occurs and can express itself What can be learned etc

How can we tell if knowledge is unconscious? 1)Use free report. 2) Wordly discriminations – if people are objectively at chance on discriminating whether a feature is relevant to a task, they cannot have conscious knowledge about the relevance of that feature 3) Subjective measures (mental state discrimination) – are people at chance at discriminating the mental state they are in?

1. Free report Mathews et al (1989) - ‘original’ subjects exposed to grammatical strings (training phase) then classified new strings (test phase). After every 10 classification decisions they gave instructions on how to classify. - ‘Yoked’ subjects followed the instructions and classified the same stimuli. They had no previous training phase.

1. Free report Mathews et al (1989) - ‘original’ subjects exposed to grammatical strings (training phase) then classified new strings (test phase). After every 10 classification decisions they gave instructions on how to classify. - ‘Yoked’ subjects followed the instructions and classified the same stimuli. They had no previous training phase. Original subjects were always about 30% better than yoked subjects Subjects acquire knowledge that could not be elicited in free report. Is this because the knowledge is in a form fundamentally incompatible with the processes of free report?

BUT Free report gives the subject the option of not stating some knowledge if they choose not to (if they are not confident enough of it); If the free report is requested some time after the decision, can be partially forgotten Subject might only try to report the sort of information they think the experimenter wants (e.g. experimenter wants rules but the subject solved the task not with rules but by remembering whole items)

2. Objective threshold (wordly discrimination) Force the subject to respond regardless of confidence, and make sure there are appropriate cues present so that the test is sensitive (cf Shanks & St John, 1994). Dulany et al (1984) After training on on grammatical strings, S classified new strings. After each classification decision, subjects underlined that part of the string that made it grammatical/ungrammatical. e.g. if MTRXR is called ungrammatical, the subject might underline: MTRXR This can be considered a consciously expressed rule: “TR cannot occur starting in the second position”

Rule validity of rule: Percentage of test strings that would be classified correctly if just this rule was applied. (If string has feature, call it nongrammatical; if string does not have feature, call it grammatical) R=0.83 slope =.99 intercept =.01 => Subjects conscious rules predicted classification performance without systematic error.

3. Subjective measures (discrimination of mental states) Does wordly discrimination really measure whether a mental state is conscious? Higher Order Thought theory – a mental state is conscious only if there is an appropriate higher order thought. Does the person know that she knows? Absence of wordly discrimination performance- good evidence for absence of conscious knowledge; but presence of wordly discrimination performance not good evidence for presence of conscious knowledge. Need a measure more tuned to conscious knowledge rather than any knowledge.

Two criteria for measuring implicit knowledge (Dienes & Berry, 1997): Guessing criterion When subjects believe they are literally guessing, is their performance above chance? Zero-correlation criterion Is their a lack of relationship between confidence and accuracy? Do subjects fail to discriminate between guessing and knowing?

The most direct way of testing for conscious knowledge is to test for higher order thoughts (Dienes, Altmann, Kwan, & Goode 1995)

The method has an advantage over free report in that - low confidence is no longer a means by which relevant conscious knowledge is excluded from measurement; rather the confidence itself becomes the object of study - can be quickly assessed on every trial - it does not matter what knowledge the subject has, we don’t need to know how the task was solved

Artificial grammar learning People asked to memorize a set of training strings Then informed of the existence of rules and asked to classify new strings as following the rules or not. Take confidence ratings in the test phase and apply guessing and zero correlation criteria. Confidence ratings given on a scale where 50= literal guess, expected performance is 50% 100 = complete certainty, expected performance is 100%

Intercept above 0 => some unconscious knowledge Slope > 0 => some conscious knowledge Dienes, Altmann, Kwan, & Goode(1995). Advantage of trained group over untrained baseline: Artificial grammar learning

Problem with subjective measures: The possibility of bias in reporting mental states Do people say they are guessing when they actually feel some confidence?

Answer: Is the guessing criterion useful in separating qualitatively different types of knowledge (cf subliminal perception lectures). It might be: separating knowledge resistant vs susceptible to secondary tasks Note: Zero correlation criterion can escape the bias problem because it looks at difference in accuracy between low and high confidence – bias cancels out

What exactly is the knowledge shown to be conscious or unconscious by the guessing and zero correlation criteria?

Training phase -> knowledge of structure of training items (structural knowledge) Test phase -> knowledge that an item does or does not have that structure (judgment knowledge)

Presumably, conscious structural knowledge leads to conscious judgment knowledge But if structural knowledge is unconscious, judgment knowledge could be conscious or unconscious. Consider natural language: If shown a sentence one can know it is grammatical and consciously know that it is grammatical, but not know at all why it is grammatical

If both structural knowledge and judgment knowledge unconscious => phenomenology is of guessing If structural knowledge unconscious but judgment knowledge conscious => phenomenology is of intuition (cf natural language) In both cases, we have unconscious structural knowledge. But in second case, zero correlation and guessing criteria might show all knowledge is conscious – because those criteria only assess judgment knowledge

Dienes and Scott (2005) In test phase, subjects rated confidence in judgment and rated the basis of the judgment: 1.Guess – judgment has no basis whatsoever, may as well have flipped a coin 2.Intuition – have some confidence in judgment, but have no idea why it’s right 3.Rules – judgment based on rules acquired from the training phase I could state 4.Memory – judgment based on memory for training strings or parts of training strings

Independent variables: 1.In the training phase, urged to search for rules or just memorize exemplars. Rule search should encourage the development of conscious structural knowledge. 2.In the test phase, classify with full attention or while performing a demanding secondary task (random number generation). Secondary task should interfere with the application of conscious structural knowledge.

NB: proportion correct significantly above.50 for each basis

When there was an implicit basis: No effect of learning condition nor secondary task on percentage correct When there was an explicit basis: A secondary task disrupted correct classification in the rule search condition

The conscious status of judgment knowledge, and its basis, structural knowledge, can be assessed independently by subjective measures. Unconscious structural knowledge can produce conscious judgment knowledge. The conscious/unconscious status of structural rather than judgment knowledge more sensitively reflects the effects of learning mode and secondary task.

Assessment of unconscious knowledge in other implicit learning paradigms Destrebecqz and Cleeremans (2001) SRT task Rule governed Violates rules

Then told that there were some rules; asked to generate a sequence of responses that did NOT follow the rules (exclusion task). Still generated responses that followed the rules! (p <.01) (exclusion significantly above baseline) Why might this happen?

Then told that there were some rules; asked to generate a sequence of responses that did NOT follow the rules (exclusion task). Still generated responses that followed the rules! (p <.01) (exclusion significantly above baseline) Why might this happen? Subjects think of a response – their implicit knowledge will tend to make them think of legal responses If they feel they are sure the response is legal they withhold that response; If they feel they are guessing about whether it is legal or not (they don’t know that they know) they press the key for that response.

Then told that there were some rules; asked to generate a sequence of responses that did NOT follow the rules (exclusion task). Still generated responses that followed the rules! (p <.01) (exclusion significantly above baseline) Why might this happen? Subjects think of a response – their implicit knowledge will tend to make them think of legal responses If they feel they are sure the response is legal they withhold that response; If they feel they are guessing about whether it is legal or not (they don’t know that they know) they press the key for that response. Hence this task relies on a subject’s assessment of his mental state – it is a disguised subjective measure!

Summary of methods for determining the conscious or unconscious status of knowledge: 1.Free report: Good face validity but can be very insensitive 2.Wordly discriminations: Allows only asymmetric inferences: Null discrimination good evidence for lack of conscious knowledge; but good discrimination uninformative about the conscious status of the knowledge. Further, when there is null discrimination, not only is there no conscious knowledge, but unconscious knowledge might be low, degraded or non-existent. 3.Subjective measures: Good face validity.

We have an approach for determining whether knowledge is unconscious. What properties does unconscious knowledge have? 1.You may be able to use it even when consciously distracted 2.It may have preferred constrained contents

1.You may be able to use it even when consciously distracted Unconscious knowledge does not need working memory/executive system for its application – so should apply even when distracted. Many people have tried to test this, with conflicting results (cf Jimenez, Shanks). Conflicting results may be because few tasks are pure measures of unconscious knowledge. Few people have used subjective measures to separate conscious and unconscious knowledge.

Dienes, Atmann, Kwan & Goode (1995): Training phase: People memorized some grammatical strings Test phase: Classified strings. Half the subjects simultaneously generated random numbers: every couple of seconds they said a digit, the sequence of digits had to be random (each digit follow every digit equally often etc). Half the subjects devoted all their attention to classification.

Responses divided into those the subject gave a guess response to and those the subject had some confidence in. Guessing knowledge not affected by secondary task; confident knowledge is affected. (NB: such results are also arguments against the bias problem) Performance

2. What are the contents of unconscious knowledge? In implicit learning paradigms a.People store items and classify a test string depending on how similar it is to one or more training strings (Brooks, Vokey, Higham)

2. What are the contents of unconscious knowledge? In implicit learning paradigms a.People store items and classify a test string depending on how similar it is to one or more training strings (Brooks, Vokey, Higham) b.A stored item may include details of what the subject was doing (Whittlesea: “episodic processing”)

2. What are the contents of unconscious knowledge? In implicit learning paradigms a.People store items and classify a test string depending on how similar it is to one or more training strings (Brooks, Vokey, Higham) b.A stored item may include details of what the subject was doing (Whittlesea: “episodic processing”) c.People learn fragments of strings, mainly bigrams (e.g. “MT”), but some trigrams (e.g. “XTV”) (Perruchet) In principle, the above knowledge contents could be conscious or unconscious

2. What are the contents of unconscious knowledge? In implicit learning paradigms a.People store items and classify a test string depending on how similar it is to one or more training strings (Brooks, Vokey, Higham) b.A stored item may include details of what the subject was doing (Whittlesea: “episodic processing”) c.People learn fragments of strings, mainly bigrams (e.g. “MT”), but some trigrams (e.g. “XTV”) (Perruchet) In principle, the above knowledge contents could be conscious or unconscious d. People learn by adjusting weights in a neural network, acquiring knowledge like the above, but knowledge that can grade into more abstract knowledge as well (Cleeremans)

Input units: pattern of activation codes e.g. which light is currently on in an SRT task Activation flows along the weights according to their value (synaptic strength); the value is changed with learning so that the output better matches reality Output units: prediction of which light will be on next Pattern of weights codes knowledge of sequential regularities Neural network models:

Cleeremans (1993) Used the Sequential Recurrent Network (SRN) of Elman to model sequence learning (SRT). Hidden units come to encode a variable graded window into the past. Weights encode knowledge of sequential statistical regularities in an analog, graded non-conceptual way. The ideal bearers of unconscious knowledge? Axel Cleeremans

Summary: Implicit learning is the process of acquiring knowledge you are not aware of Implicit learning can be measured in the artificial grammar, dynamic control and serial reaction time tasks. When we measure the extent to which subjects are aware of their knowledge we find: 1.Unconscious knowledge is resistant to secondary tasks 2.In tasks where people often acquire knowledge they are not aware of, the knowledge may be largely statistical