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Backward versus Forward Blocking: Evidence for Performance-Based Models of Human Contingency Learning

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Two types of theories are usually invoked to account for cue-interaction effects in human-contingency learning, performance-based theories, such as the comparator hypothesis and statistical models, and learning-based theories, such as associative models. Interestingly, the former models predict two important cue-interaction effects, forward and backward blocking, should affect responding in a similar manner, whereas learning-based models predict the effect of forward blocking should be larger than the effect of backward blocking. Previous experiments involved important methodological problems, and results have been contradictory. The present experiment was designed to explore potential asymmetries between forward and backward blocking. Analyses yielded similar effect sizes, thereby favoring the explanation by performance-based models.
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Psychological Reports, 2011, 109, 3, 1001-1016. © Psychological Reports 2011
DOI 10.2466/22.23.PR0.109.6.1001-1016 ISSN 0033-2941
BACKWARD VERSUS FORWARD BLOCKING:
EVIDENCE FOR PERFORMANCE-BASED MODELS
OF HUMAN CONTINGENCY LEARNING1, 2
DAVID LUQUE
Departamento de Psicología Básica
Universidad de Málaga
MIGUEL A. VADILLO
Departamento de Fundamentos
y Métodos de la Psicología
Universidad de Deusto
Summary.—Two types of theories are usually invoked to account for cue-in-
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D. LUQUE & M. A. VADILLO
1002





      -


→ 
→ 
  
→ → → O1 asso-


        -

performance-based models. According to this
      -
   

 
 

to the strength of the B–O association and inversely proportional to the


  -

        -

       
TABLE 1

Group Phase 1 Phase 2 Test
Forward  

B?
C? / D?
Backward 


Note  

-

BACKWARD VS FORWARD BLOCKING 1003
  
            
-

-



-

-

     
         

   
-

         
 
-
   
          
   -
   -
es in associative strength of the target Cue B during learning phases. For
       
       
  -

-

    -
 

were presented together. However, this process does not occur in forward

-
-
      
    

D. LUQUE & M. A. VADILLO
1004
       
-
   
-

-




   -
   
     
       -
→ → -


   
→ -



        -

       -
           
      
      



    
 -

       
         -
     et al.   et al.
    
       
et al.et al.

et al.
et al.
BACKWARD VS FORWARD BLOCKING 
included appropriate control conditions for children as participants. In


  -
          
         -
          et
al.et al.
-


 -

       
     
the patient on a particular occasion. Then, they have to guess whether the



-

-


-
es that participants have to rate the strength of the causal -
et al



 
On the other hand, the two studies conducted with children used

et al.
    
-

et al.,
 et al.      
     
 et al.et al. 
-
-
D. LUQUE & M. A. VADILLO
1006


-
      
     -
       

-

  -

       
-


-
 -
et al.et al.et al.,
       et al.   -

      
et al.
Mitchell, et al.
    -
-


 et al. 


-
-

-



    
on the allergy task.

Participants and Apparatus
Fort-
BACKWARD VS FORWARD BLOCKING 
-
-

Design and Procedure

          
     
3 
    




   et al  
        
-
-



    


-
-
       -

-

-

corresponding option on each trial.
-
  -
       

 


3       
  
to C and to D.
D. LUQUE & M. A. VADILLO

  

-




-
      
        




          
        

-


F              
   

     


 
across trials.
(A) (B) (C)

-

-
BACKWARD VS FORWARD BLOCKING 1009
      


    Mean correct re-

-

         


         -
cant, as participants in the Backward group responded during the test





 -


-
    
-
-

          

TABLE 2

Measure Group  
M SEM M SEM
Correct RFB 9.9 3.3 16.0 
BB  6.6  6.9
Correct–Incorrect FB    
BB 2.1   
% Correct RFB 44.3   
BB  9.0  
Note             


     -

responses, and percent of correct responses.
D. LUQUE & M. A. VADILLO
1010



  

  

             -
 -




 
-
     

         

-
ures of responding.

       -
TABLE 3

Analysis Dependent

 F1,42 MSE p η2β
ANOVA:


Correct
responses
Cue   .03* 0.11 0.60
Group 10.94   0.21 0.90
Cue*
Group 0.62  .44 0.02 0.12
ANOVA:


All responses Cue 1.63 990.6 .21 0.11 0.24
Group     0.99
Cue*
Group 0.33 990.6  0.02 
ANOVA:



incorrect
Cue   .04* 0.10 
Group 0.91   0.02 
Cue*
Group   .22 0.04 0.23
ANOVA:


% Correct
responses
Cue     
Group 0.91  .16  0.29
Cue*
Group   .19 0.04 
*p
BACKWARD VS FORWARD BLOCKING 1011
         -
  

        -
-
     
 -
et al.et al.

         
          et al.
et al.-


-
   

their participants were adults.
   
 
 

     
-

-
-

  

         
-
-

          

           



  


D. LUQUE & M. A. VADILLO
1012
-
-

   
         -
et al.


et al
      
-
   


et al.et al.

hard to reconcile with a lack-of-sensitivity hypothesis.


   -
-
et al.et al.et al., 2004,
et al.-
       
      -
             
-


        
 -
during learning. In this
      



-

et al.,
reluctant to conclude that these results are consistent or not with the prop-

in the present learning task.
BACKWARD VS FORWARD BLOCKING 1013
REFERENCES
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Learning & Behavior,

        &     
         -
  Quarterly Journal of Experimental Psychology,   

& 
-
dren. Experimental Psychology,  OI
       
Journal of Experimental Psychology: Learning, Memory, and Cognition, 
&-
Compara-
tive approaches to cognitive science
 -
Learning & Behavior, 
   &       
Quarterly Journal of Experimental Psychol-
ogy
 & -
Quarterly Journal of Experimental Psy-
chology, 
 &  
Proceedings of the 22nd Annual
Conference of the Cognitive Science Society
&  
Learning and Motivation, 33,

&
         
inferences. Memory & Cognition, 33, 
&-
           
Memory & Cognition, 31, 133-142.
&-

Learning and Motivation, 
&     
Behavioural Processes, 
&
 Behavioural Processes
332.
&

learning tasks. Psychological Record
D. LUQUE & M. A. VADILLO
1014
&
and young children’s causal and counterfactual inferences. Developmental Psychol-
ogy, 
    &    
          
theory. Quarterly Journal of Experimental Psychology, 
&
       
Experimental Psychology
   &-

. Journal of Experimental Psychology: Learning, Memory,
and Cognition, 19, 
&
The psychology of learning and
motivation
& 
Behavioral and Brain Sciences, 
    &
-
ship. Quarterly Journal of Experimental Psychology, 
        &      
       Journal of
Experimental Psychology: Animal Behavior Processes, 
Annual Review of Psychol-
ogy, 
 &   
Acta Psychologica, 122, 234-246.
&
Learning and Motiva-
tion, 
   &       
-
tions. Quarterly Journal of Experimental Psychology, 
&
Learning & Behavior, 33, 131-146.
Accepted December 7, 2011.
BACKWARD VS FORWARD BLOCKING 
APPENDIX

        u will have to earn as

 -
ral intervals or trials. During these trials, you will have to learn the re-
       
-
ed with the coloured rectangles that appear at the top of the screen. The

     
  

total score.





  


-
over, the points that you can earn or lose could increase if you keep the

to the plant related to the coloured rectangles at the top of the screen. If



  -

  
 

The wrong plants will disappear so you can see which is the correct one.
Therefore, you will know if you are doing it right. For your convenience,




           
   -
D. LUQUE & M. A. VADILLO
1016
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
in each trial.

-
     -
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
        

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


... In the second case, when the previous belief is that A prevents the outcome from occurring, the detection of a causal relationship between the second cause B and the outcome will be facilitated (i.e., this particular case of cue interaction is generally known as superconditioning; Rescorla, 1971). Many cue interaction experiments, both with animals and humans, show that learning about the relationship between a potential cause and an outcome can result altered when the potential cause is presented in compound with another potential cause that has been previously associated either with the outcome or its absence (Aitken, Larkin, & Dickinson, 2000;Arcediano, Matute, Escobar, & Miller, 2005;Dickinson, Shanks, & Evenden, 1984;Kamin, 1968;Luque, Flores, & Vadillo, 2013;Luque & Vadillo, 2011;Mor ıs, Cobos, Luque, & L opez, 2014;Rescorla, 1971;Shanks, 1985). ...
... Nevertheless, what is clear given the present results is that the group who developed a high illusion about the ineffective Medicine A tended to assess the effective Medicine B as less effective than the group who developed a weaker illusion. Similar cue interaction effects have been clearly established in other causal learning research (Aitken et al., 2000;Arcediano et al., 2005;Dickinson et al., 1984;Luque & Vadillo, 2011;Luque et al., 2013;Mor ıs et al., 2014;Shanks, 1985). Moreover, cue interaction effects are beautifully predicted by current theories of learning (Rescorla & Wagner, 1972). ...
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Cognitive illusions are often associated with mental health and well-being. However, they are not without risk. This research shows they can interfere with the acquisition of evidence-based knowledge. During the first phase of the experiment, one group of participants was induced to develop a strong illusion that a placebo medicine was effective to treat a fictitious disease, whereas another group was induced to develop a weak illusion. Then, in Phase 2, both groups observed fictitious patients who always took the bogus treatment simultaneously with a second treatment which was effective. Our results showed that the group who developed the strong illusion about the effectiveness of the bogus treatment during Phase 1 had more difficulties in learning during Phase 2 that the added treatment was effective.
... First, although there are more robust retroactive cue competition effects in HCL than expected on the basis of Pavlovian conditioning observations and theories (e.g., Luque & Vadillo, 2011;Shanks, 1985), it has been most common to observe lesser retroactive than proactive effects (e.g., Chapman, 1991;Lovibond, Been, Mitchell, Bouton, & Frohardt, 2003;Melchers, Lachnit, & Shanks, 2004Mitchell, Lovibond, Minard, & Lavis, 2006). ...
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Five experiments involving human causal learning were conducted to compare the cue competition effects known as blocking and unovershadowing, in proactive and retroactive instantiations. Experiment 1 demonstrated reliable proactive blocking and unovershadowing but only retroactive unovershadowing. Experiment 2 replicated the same pattern and showed that the retroactive unovershadowing that was observed was interfered with by a secondary memory task that had no demonstrable effect on either proactive unovershadowing or blocking. Experiments 3a, 3b, and 3c demonstrated that retroactive unovershadowing was accompanied by an inflated memory effect not accompanying proactive unovershadowing. The differential pattern of proactive versus retroactive cue competition effects is discussed in relationship to amenable associative and inferential processing possibilities.
... Not surprisingly, many learning experiments conducted with similar tasks rely on a slightly different dependent measure that takes into account not only the responses to the correct outcome, but also the responses to the incorrect ones (e.g., see Rosas et al., 2001). In previous experiments conducted with this specific task (e.g., Luque & Vadillo, 2011), we have also found that the number of points earned (i.e., the number of correct responses minus the number of incorrect responses) can provide a more precise assessment of learning processes. Therefore, we used this measure as our main dependent variable in the present experiment. ...
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Current associative theories of contingency learning assume that inhibitory learning plays a part in the interference between outcomes. However, it is unclear whether this inhibitory learning results in the inhibition of the outcome representation or whether it simply counteracts previous excitatory learning so that the outcome representation is neither activated nor inhibited. Additionally, these models tend to conceptualize inhibition as a relatively transient and cue-dependent state. However, research on retrieval-induced forgetting suggests that the inhibition of representations is a real process that can be relatively independent of the retrieval cue used to access the inhibited information. Consistent with this alternative view, we found that interference between outcomes reduces the retrievability of the target outcome even when the outcome is associated with a novel (non-inhibitory) cue. This result has important theoretical implications for associative models of interference and shows that the empirical facts and theories developed in studies of retrieval-induced forgetting might be relevant in contingency learning and vice versa.
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Shanks (1991) reported experiments that show selective-learning effects in a categorization task, and presented simulations of his data using a connectionist network model implementing the Rescorla-Wagner (R-W) theory of animal conditioning. He concluded that his results (a) support the application of the R-W theory to account for human categorization, and (b) contradict a particular variant of contingency-based theories of categorization. We examine these conclusions. We show that the asymptotic weights produced by the R-W model actually predict systematic deviations from the observed human learning data. Shanks claimed that his simulations provided good qualitative fits to the observed data when the weights in the networks were allowed to reach their asymptotic values. However, analytic derivations of the asymptotic weights reveal that the final weights obtained in Shanks' Simulations 1 and 2 do not correspond to the actual asymptotic weights, apparently because the networks were not in fact run to asymptote. We show that a contingency-based theory that incorporates the notion of focal sets can provide a more adequate explanation of cue competition than does the R-W model.
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D. R. Shanks (1991) reported experiments that show selective-learning effects in a categorization task, and presented simulations of his data using a connectionist network model implementing the Rescorla-Wagner (R-W) theory of animal conditioning. He concluded that his results (1) support the application of the R-W theory to account for human categorization, and (2) contradict a particular variant of contingency-based theories of categorization. These conclusions are examined. It is shown that the asymptotic weights produced by the R-W model actually predict systematic deviations from the observed human learning data. Shanks claimed that his simulations provided good qualitative fits to the observed data when the weights in the networks were allowed to reach their asymptote. However, analytic derivations of the asymptotic weights reveal that the final weights obtained in Shanks's Simulations 1 and 2 do not correspond to the actual asymptotic weights, apparently because the networks were not in fact run to asymptote. It is also shown that a contingency-based theory that incorporates the notion of focal sets can provide a more adequate explanation of cue competition than does the R-W model. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
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Backward blocking (BB) and interference between cues (IbC) are cue competition effects produced by very similar manipulations. In a standard BB design both effects might occur simultaneously, which implies a potential problem to study BB. In the present study with humans, the magnitude of both effects was compared using a non causal scenario and a within subjects design. Previous studies have made this comparison using learning tasks framed within causal scenarios. This posits a limit to generalizing their findings to non-causal learning situations because there is ample evidence showing that participants engage in causal reasoning when tasks are causally framed. The results obtained showed BB and IbC effects of the same magnitude in a non causal framed task. This highlights the methodological need for an IbC control in BB experiments.
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Dickinson and Burke (1996) proposed a modified version of Wagner's (1981) SOP associative theory to explain retrospective revaluation of human causal judgments. In this modified SOP (MSOP), excitatory learning occurs when cue and outcome representations are either both directly activated or both associatively activated. By contrast, inhibitory learning occurs when one representation is directly activated while the other is associatively activated. Finite node simulations of MSOP yielded simple acquisition, overshadowing, blocking, and inhibitory learning under forward contingencies. Importantly, retrospective revaluation was predicted in the form of unovershadowing and backward inhibitory learning. However, MSOP did not yield backward blocking. These predictions are evaluated against the relevant empirical evidence anti contrasted with the predictions of other associative theories that have been applied to retrospective revaluation of human causal and predictive learning.
Chapter
This chapter describes the potential explanatory power of a specific response rule and its implications for models of acquisition. This response rule is called the “comparator hypothesis.” It was originally inspired by Rescorla's contingency theory. Rescorla noted that if the number and frequency of conditioned stimulus–unconditioned stimulus (CS–US) pairings are held constant, unsignaled presentations of the US during training attenuate conditioned responding. This observation complemented the long recognized fact that the delivery of nonreinforced presentations of the CS during training also attenuates conditioned responding. The symmetry of the two findings prompted Rescorla to propose that during training, subjects inferred both the probability of the US in the presence of the CS and the probability of the US in the absence of the CS and they then established a CS–US association based upon a comparison of these quantities. The comparator hypothesis is a qualitative response rule, which, in principle, can complement any model of acquisition.
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College students rated the causal efficacy of Elements X, A, and B of food compounds AX and BX in producing the allergic reaction of a hypothetical patient. The results of a 16-day allergy test were presented to subjects in a serial, trial-by-trial manner. The response format used was a running estimate, in which subjects were asked to rate all of the three foods after each of the 16 trials. Ratings of distinctive Elements A and B diverged and ratings of common Element X decreased as the difference in the correlation of AX and BX with the occurrence and nonoccurrence of the allergic reaction increased. These human causal judgments closely correspond with stimulus selection effects observed in the conditioned responses of animals in associative learning studies. The experiment also directly demonstrated the fact that significant changes in the causal ratings of a stimulus occur on trials in which the cue is not presented. Associative theories such as that of Rescorla and Wagner (1972) predict changes in associative strength only for those stimulus elements that are presented on a particular trial. A modification of the Rescorla-Wagner model is described that correctly predicts immediate changes in the associative strengths of all relevant cues on each trial—whether presented or not.
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The influence of a secondary task on forward blocking of human contingency ratings was examined. A smaller blocking effect was found when participants performed a highly demanding secondary task than when they performed a less demanding secondary task. The modulatory effect of secondary task difficulty was significant only when the secondary task was administered during both the learning and the test phase of the contingency judgement task. The results suggest that forward blocking in human contingency learning cannot be fully accounted for by associative processes. Instead, forward blocking seems to depend at least partially on deliberate deductive reasoning processes.
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In an interference-between-cues design (IbC), the expression of a learned Cue A–Outcome 1 association has been shown to be impaired if another cue, B, is separately paired with the same outcome in a second learning phase. The present study examined whether IbC could be caused by associative mechanisms independent of causal reasoning processes. This was achieved by testing participants in two different learning situations. In the Causal Scenario condition, participants learned in a diagnostic situation in which a common cause (Outcome 1) caused two disjoint effects, namely Cues A and B. In the Non-Causal Scenario condition, the same IbC design and stimulus conditions were used. However, instructions provided no causal frame to make sense of how cues and outcomes were related. IbC was only found in the Causal Scenario condition. This result is consistent with Causal Reasoning Models of causal learning and raises important difficulties for associative explanations of IbC.
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It has recently been suggested that patients with semantic breakdown may show the phenomenon of so-called "naming without semantics". If substantiated, this finding would clearly have a major impact on theories of face and object processing, all of which assume that access to semantic knowledge is a prerequisite for successful naming. In order to investigate this issue, we studied recognition, identification (the ability to provide accurate information), and naming of 50 famous faces by 24 patients with mild to moderate dementia of Alzheimer type (DAT) and 30 age-matched controls. The DAT group was impaired in all three conditions. An analysis of the concordance between identification and naming by each patient, for each stimulus item, established that naming a famous face was possible only with semantic knowledge sufficient to identify the person. Our data support the hypothesis that naming is not possible unless semantic information associated with the target is available. Naming without semantics, therefore, did not occur in patients with DAT. By contrast, there were 206 instances (17% of the total responses) in which the patients were able to provide detailed, accurate identifying information yet were unable to name the person represented. The implication of these findings for models of face identification and naming are discussed.