Dele af Kahnemans ‘At tænke – hurtigt og langsomt’ hviler på et tyndt grundlag

 

/mennesker

Du kender sikkert – eller har måske hørt om – Daniel Kahnemans bog fra 2011, ‘At tænke – hurtigt og langsomt’, eller ‘Thinking, Fast and Slow’ på originalsproget. Jeg har endnu ikke selv læst bogen, så hvis du vil vide mere om den, må du spørge en anden eller læse om bogen på Wikipedia.

(Pssst! Alle links i denne artikel er samlet til slut.)

En del af bogen (kapitel 4) handler om begrebet “priming”, der kort fortalt går ud på association. Altså, hvis du bliver eksponeret for fx et ord, kan det påvirke dine handlinger – måske endda din kunnen. Et uddrag fra bogen (på engelsk):

In the 1980s, psychologists discovered that exposure to a word causes immediate and measurable changes in the ease with which many related words can be evoked. If you have recently seen or heard the word EAT, you are temporarily more likely to complete the word fragment SO_P as SOUP than as SOAP. The opposite would happen, of course, if you had just seen WASH. We call this a priming effect and say that the idea of EAT primes the idea of SOUP, and that WASH primes SOAP.

Priming effects take many forms. If the idea of EAT is currently on your mind (whether or not you are conscious of it), you will be quicker than usual to recognize the word SOUP when it is spoken in a whisper or presented in a blurry font. And of course you are primed not only for the idea of soup but also for a multitude of food-related ideas, including fork, hungry, fat, diet, and cookie. If for your most recent meal you sat at a wobbly restaurant table, you will be primed for wobbly as well. Furthermore, the primed ideas have some ability to prime other ideas, although more weakly. Like ripples on a pond, activation spreads through a small part of the vast network of associated ideas. The mapping of these ripples is now one of the most exciting pursuits in psychological research.

Der er bare et problem: Der er nemlig for nylig blevet sat spørgsmålstegn ved mange af de undersøgelser og den forskning, som Kahneman baserer sit kapitel på.

R-indekset

Det kræver lige lidt forklaring. For nylig lyttede jeg til et podcast med titlen ‘On The Media’. I den pågældende episode (‘Doubt It’ fra 21. juli) er der en gæst i studiet, Ulrich Schimmack.

Han står bag en metode til at finde ud af, hvor let det er at genskabe resultaterne fra en undersøgelse eller forskningsforsøg. Jo lettere at genskabe, jo højere trovædighed. Dette udtrykker Schimmack og hans kolleger ved det såkaldte ‘Replicability-Index’, eller blot ‘R-Index’. Jo højere R-Index jo bedre.

I podcast-udsendelsen nævner værten, at en af de større opdagelser i forbindelse med R-indekset var en opdagelse omkring Kahnemans bog. Hans kilder til kapitlet om “priming” lader en del tilbage at ønske.

Her er “abstractet” (et sammenfattede uddrag) fra Schimmack og kollegers artikel om kapitel 4 i ‘At tænke – hurtigt og langsomt’:

We computed the R-Index for studies cited in Chapter 4 of Kahneman’s book “Thinking Fast and Slow.” This chapter focuses on priming studies, starting with John Bargh’s study that led to Kahneman’s open email. The results are eye-opening and jaw-dropping. The chapter cites 12 articles and 11 of the 12 articles have an R-Index below 50. The combined analysis of 31 studies reported in the 12 articles shows 100% significant results with average (median) observed power of 57% and an inflation rate of 43%. The R-Index is 14. This result confirms Kahneman’s prediction that priming research is a train wreck and readers of his book “Thinking Fast and Slow” should not consider the presented studies as scientific evidence that subtle cues in their environment can have strong effects on their behavior outside their awareness.

Den e-mail, der henvises til, er Kahnemans “A proposal to deal with questions about priming effects” [PDF: 2 sider] fra 26. september 2012. Her skriver han blandt andet:

For all these reasons, right or wrong, your field is now the poster child for doubts about the integrity of psychological research. Your problem is not with the few people who have actively challenged the validity of some priming results. It is with the much larger population of colleagues who in the past accepted your surprising results as facts when they were published. These people have now attached a question mark to the field, and it is your responsibility to remove it.

Av.

Og fra ‘Replicability-Index’-artiklen:

Five years later, Kahneman’s concerns have been largely confirmed. Major studies in social priming research have failed to replicate and the replicability of results in social psychology is estimated to be only 25% (OSC, 2015).

Looking back, it is difficult to understand the uncritical acceptance of social priming as a fact. In “Thinking Fast and Slow” Kahneman wrote “disbelief is not an option. The results are not made up, nor are they statistical flukes. You have no choice but to accept that the major conclusions of these studies are true.”

Yet, Kahneman could have seen the train wreck coming. In 1971, he co-authored an article about scientists’ “exaggerated confidence in the validity of conclusions based on small samples” (Tversky & Kahneman, 1971, p. 105). Yet, many of the studies described in Kahneman’s book had small samples. For example, Bargh’s priming study used only 30 undergraduate students to demonstrate the effect.

Altså er der god grund til at udvise en stor portion skepsis, hvad angår “priming” – og selvfølgelig som altid litteratur, der baserer sig på forskningsresultater.

🏁

Læs mere:

» Wikipedia: Thinking, Fast and Slow

» Læs mere om ‘On The Media’-podcast’en

» On The Media: Doubt It [21. juli 2017]

» Ulrich Schimmack, Moritz Heene og Kamini Kesavan: Reconstruction of a Train Wreck: How Priming Research Went off the Rails [Replicability-Index / 2. februar 2017]

» Daniel Kahneman: A proposal to deal with questions about priming effects [Nature.com / 26. september 2012 / PDF: 2 sider]

» Foto: Neil Conway / Flickr Creative Commons

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