Blocking Paradigm. Conditioned Learning Variables

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Table of Contents

Abstract
Experimental Design
Statement of the Problem
Hypotheses to be Investigated
Results
References

Abstract

Introduction/Brief Review of Literature

An entire body of theoretical work and a practical framework underlies the contributions of conditioned learning. How humans learn and retain what they do has implications far beyond the academic environment. Among children and adolescents with autism spectrum conditions, for example, conditioned learning experiments employing an aversive unconditioned stimulus (US) have enabled researchers to hypothesize that a dysfunctional amygdala explains both poor facial recognition and chronic anxiety. In these parlous times, when recessionary unemployment trends afflict millions of Americans, human resource professionals cast about for the most efficient methods with which to structure retraining for career change or technological upgrades in the same job setting. Other matters that conditioned learning concepts might address include finding solutions to meet the admirable goals of “No Child Left Behind”. Or for a profession that prides itself on great depth of scientific learning, how do physicians avoid sustained trial-and-error prescribing behavior when there is great uncertainty about the etiology of presenting symptoms?

Since much of learning is rather more complex than the classical single S-R experiments of Pavlov and Skinner, the field has progressed to assess what happens when humans are presented with dual stimuli, of which none or one has been previously conditioned. In the context of the experiment conducted, learning success or failure in a block presentation can theoretically be attributed to the operation of pre-conditioning, selective attention, surprise, and categorization.

The basic blocking model involves the compound conditioned stimulus, consisting of both A and B. Mere proximity in time does not guarantee conditioning, especially if an association between only A and the US had already been established beforehand. When presented singly afterwards, in fact, A is therefore more likely to provoke the conditioned response of interest. (Kamin, 1967, as cited in Roitblat, Bever, & Terrace, 1984).

Roitblat et al. (1984) explain the processes underlying success or failure to provoke the desired conditioned response by reference to information processing and rehearsal. The first infers that humans and indeed any other animal processes information from their environment to try and make sense of the contingency it is presented with (citing Kamin, 1969). Citing Wagner (1978, 1981), the authors also offered up the idea of associative learning and rehearsal, the latter taking place for stimulus B in the above blocking model only when the state of the US changes (presence/absence or intensity) contingent on B.

In the course of the Assignment 2 experimental design, however, there is only one sequence (Phase 1: A+, Phase 2: AB+) where participants had effectively received a “pre-trial” with one food of the stimulus pair. Presumably, this variable designator means both CS’s are allergens. There being no conflict in that regard, blocking should have no adverse effect on learning rate.

The GH(-), T(-) and V(-) stimuli screens occur in both phases but with no reinforcement. Neither pre-trial nor blocking affects learning one way or the other. Over a long series of runs, therefore, the results should be purely random or 50-50 odds.

Other constructs that might be relevant to evaluating conditioned learning trial under blocking are attention and surprise (Kamin, 1969). The valid sequence that might evaluate attention as a confounding variable – A, AB, B – was not, however, implemented in this experiment. And in any case, artificial levels of attention are to be expected for a laboratory setting such as was used in this experiment and, personal food preferences aside, attention should work only for the pre-trial CS.

Kamin operationalizes surprise (conditioned emotional response, CER) by subjecting laboratory rats in an operant conditioning chamber to a low-level shock, disagreeable noise or sudden bright light (the environment was dark after the initial conditioning trials). Naturally, the effect of an aversive stimulus was to rapidly suppress bar-pressing behavior. All in all, the experimental series Kamin describes in the cited chapter led him to wonder whether blocking hinders learning because of an attention deficit or some inability to process an association with the US since the organism had no prior experience to fall back on with respect to the new CS in the pair.

Other theories have been put forward, notably to explain human learning. There is, for example, categorization springing from “networks of association”. Contingency learning employing at least two cues seem relevant to classical conditioning, category learning, and causal induction, with the last reminding us that humans also deem themselves superior for being capable of causal learning, the ability to retrospectively deduce causes from perceptible effects.

Experimental Design

The research design confronted the student-participants with a sustained series of ten food visuals, taken singly or in pairs. Without the benefit of prior knowledge or any cue at all, each participant had to guess if the food types were bound to cause an allergic reaction(+ in the stimulus list below) or not (-). Fifteen students participated in a two-phase sequence of visuals. For those in the upper half of the grid below, immediate reinforcement was received as to whether the answer was right or wrong. In yet a third phase, learning retention was tested with a checklist where participants had to categorize the same foods as allergens or not.

	PHASE I	PHASE II
Reinforced	Pear alone =A(+) Chicken & Potpie = EF (+)	Bread & Mushrooms = CD(+) Pear & Bread = AB(+) Chicken alone = E(+)
No reinforcement	Coffee & Rice = GH(-) Ham alone = T(-) Ice cream alone = V(-)	Coffee & Rice = GH (-) Ham alone T(-) Ice cream alone = V(-)

Regardless of phase, participants were exposed to each visual five times for a total of 30 trials in Phase I and 36 in Phase II.

Statement of the Problem

What is the effect of blocking on progressive learning and retention?

With respect to pears for instance, this research question specifically investigates the matter of whether blocking has a positive effect (when presented in the pair AB in Phase II), a neutral effect, or an adverse effect on learning that food code A is a true allergen.
Is the allergen status of food E (chicken) more readily learned when presented alone or when blocked with food F?
What is the effect of reinforcement on learning rate and retention?
Is there an interaction effect between blocking and reinforcement?
How much better do the EF, CD and AB pairs fare for giving participants the benefit of immediate reinforcement vis-à-vis unreinforced block GH?

Hypotheses to be Investigated

H₀¹ : There is no difference in primary learning rate (correctly identifying as an allergen) for food code A whether presented singly or in a block.
H₀² : There is no difference in learning retention (average rating as an allergen in the third stage checklist) for food code A whether presented singly or in a block.
H₀³ : There is no difference in primary learning rate for food code E whether presented singly or in a block with food F.
H₀⁴ : There is no difference in learning retention for food code E whether presented singly or in a block with food F.
H₀⁵ : There is no difference in primary learning rate (percentage of correct answers in both phases I and II) between the six foods presented with reinforcement and the no-reinforcement condition for four of the food types.
H₀⁶ : There is no difference in learning retention (average rating as an allergen in the third stage checklist) between the six foods presented with reinforcement and the no-reinforcement condition for four of the food types.
H₀⁶ : There is no difference in primary learning rate (average percentage of correct answers in both phases I and II) among the four test conditions: I (presented singly, reinforced), II (block presentation, reinforced), III (presented singly, unreinforced), and IV (block presentation, reinforced).
H₀⁷ : There is no difference in learning retention (average rating as an allergen in the third stage checklist) among the four test conditions: I (presented singly, reinforced), II (block presentation, reinforced), III (presented singly, unreinforced), and IV (block presentation, reinforced).

Results

Effects of Block Presentation

H₀¹ requires a test of the overall average correct answers between singleton and block presentations of food type A (pear). The values marked in red below are proportions of correct answers to a two-level (Yes/No) categorical variable, hence the likely test of significance is a one-sample binomial test that approximates the Z test for large samples.

References

Kamin, L. J. (1969). Predictability, surprise, attention and conditioning. In B. A. Campbell and R. M. Church (Eds.), Punishment and Aversive Behavior (279-296). New York: Appleton-Century-Crofts.

Roitblat, H. L., Bever, T. G. & Terrace, H. S. (1984). Animal cognition: Proceedings of the Harry Frank Guggenheim Conference, June 2-4, 1982. Hove, East Sussex: Psychology Press.

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