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Blocking effect
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<h2 id="comparator">Comparator</h2> <p>While some argue that blocking demonstrates that the organism did not learn the association between the CS2 and the US, this is not necessarily the case. For instance, after a traditional blocking paradigm, the CS2 does not elicit a response (alone). However, if the response to the CS1 is extinguished, the organism will begin to respond to CS2 alone. This demonstrates that the association between the CS2 and the US was initially learned but in comparison to the stronger predictive value of the CS1 there is no conditioned response. However, after extinction, the CS2 does have more predictive value than the now extinguished CS1.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> However, this finding was not replicated in a later, similar study.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> </p> <h2 id="backward-blocking">Backward blocking</h2> <p>The reverse of blocking is often called backward blocking. In backward blocking, the subject is exposed to the compound stimulus (CS1 and CS2 together) first, and only later to CS1 alone. In some human and animal studies, subjects show a reduction in the association between CS2 and the US, though the effect is often weaker than the standard blocking effect, and vanishes under some conditions. This effect is not predicted by the <a href="/facts/Rescorla%25E2%2580%2593Wagner_model/6ne0Wuq5">Rescorla–Wagner model</a> although other models have been proposed that capture this effect. </p> <h2 id="robustness-of-the-effect">Robustness of the effect</h2> <p>Maes and colleagues reported fifteen experiments that attempted to replicate the blocking effect. None of them succeeded despite using procedures well-established in previous literature.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> They argue that <a href="/facts/Publication_bias/Wbmr1WjW">publication bias</a> may have produced a false confidence in the robustness of the effect.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> However, Soto (2018) has questioned this conclusion arguing that they come as a consequence of the type of stimuli used in these studies, and shows how contemporary models of associative learning can predict these results on the basis of this observation.<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/Classical_conditioning/ddtohoz3">Classical conditioning</a></li> <li><a href="/facts/Rescorla%25E2%2580%2593Wagner_model/6ne0Wuq5">Rescorla–Wagner model</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Kamin, L.J. (1969). Predictability, surprise, attention and conditioning. In B.A. Campbell & R.M. Church (eds.), Punishment and aversive behavior, 279–96, New York: Appleton-Century-Crofts <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Bouton, M. E.(2007) Learning and Behavior: A Contemporary Synthesis Sunderland, MA: Sinauer <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Blaisdell, A., Gunther, L. & Miller, R. (1999). Recovery from blocking achieved by extinguishing the blocking CS. Animal Learning & Behavior, 27, 63-76. <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Holland, P. (1999). Overshadowing and blocking as acquisition deficits: No recovery after extinction of overshadowing or blocking cues. The Quarterly Journal of Experimental Psychology, 52B, 307-333. <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Skibba, Ramin (26 September 2016). "Psychologists fail to replicate well-known behaviour linked to learning". Nature. doi:10.1038/nature.2016.20659. Retrieved 10 September 2017. In every case, they failed to observe a statistically significant blocking effect. <a href="http://www.nature.com/news/psychologists-fail-to-replicate-well-known-behaviour-linked-to-learning-1.20659" target="_blank">http://www.nature.com/news/psychologists-fail-to-replicate-well-known-behaviour-linked-to-learning-1.20659</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>Maes, E.; Boddez, Y.; Alfei, J. M.; Krypotos, A.-M.; D'Hooge, R.; De Houwer, J.; Beckers, T. (2016). "The elusive nature of the blocking effect: 15 failures to replicate". Journal of Experimental Psychology: General. 145 (9): e49 – e71. doi:10.1037/xge0000200. hdl:1854/LU-7241679. PMID 27428670. <a href="https://biblio.ugent.be/publication/7241679" target="_blank">https://biblio.ugent.be/publication/7241679</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Soto, F. A. (2018). Contemporary associative learning theory predicts failures to obtain blocking: Comment on Maes et al.(2016). [1] <a href="http://ccnlab.fiu.edu/Docs/JEPG.17.s.pdf" target="_blank">http://ccnlab.fiu.edu/Docs/JEPG.17.s.pdf</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> </ol>