Monday, August 20, 2007

Don’t think about it

Dijksterhuis and colleagues at the University of Amsterdam found that the unconscious intuition is better than conscious cogitation for some complex problems. I’ve wondered for a while whether Halford & Co’s finding that humans can process at most four independent variables simultaneously would change if one biased the test towards subconscious thinking. The Dijksterhuis work suggests that it might increase the number of processable variables. (See below for references.)

Dijksterhuis et al. (2006) hypothesized that decisions that require evaluating many factors may be better done by the sub-conscious. In one experiment, they asked volunteers to choose a car based on four attributes. This was easy to do, though the choice was constructed to be pretty easy. When subjects were then asked to think through a dozen attributes, they did no better than chance though. However, when distracted so that thinking took place subconsciously, they did much better. Conclusion: conscious thinkers were better able to make the best choice among simple products, whereas unconscious thinkers were better able to make the best choice among complex products.

Halford defines the complexity of a cognitive process as the number of interacting variables that must be represented in parallel to implement that the most complex step in a process (see Halford et al. 1998 for a review). He argues that relational complexity is a serviceable metric for conceptual complexity. Halford et al. (2005) found that a structure defined on four independent variables is at the limit of human processing capacity. Participants were asked to interpret graphically displayed statistical interactions. Results showed a significant decline in accuracy and speed of solution from three-way to four-way interactions; performance on a five-way interaction was at a chance level.

The Amsterdam experiment wasn’t equivalent, because the variables weren’t independent – it seems the decision was a matter of counting the number of positive attributes in the case of car choice. (One car was characterized by 75% positive attributes, two by 50% positive attributes, and one by 25% positive attributes.) Dijksterhuis et al. define complexity as “the amount of information a choice involves;” more attributes therefore means higher complexity. I don’t know how to map between the Dijksterhuis and Halford complexity metrics.

Still, I’ve wondered about what might happen if subjects had to only seconds to guess at the graphical comparisons used in Halford et al. (1998), rather than finding the answer by deliberation. If they were given Right/Wrong feedback as they went, they might intuitively learn how to guess the answer. (I’m thinking of something like this simulation of the Monty Hall game.) If this were the case, it could undermine my claims about the innate limits to software innovation for large pieces of code (or projects in general) with large numbers of independent variables.


Ap Dijksterhuis, Maarten W. Bos, Loran F. Nordgren, and Rick B. van Baaren (2006)On Making the Right Choice: The Deliberation-Without-Attention Effect
Science 17 February 2006 311: 1005-1007 [DOI: 10.1126/science.1121629]

Graeme S. Halford, Rosemary Baker, Julie E. McCredden, John D. Bain (2005)
How Many Variables Can Humans Process? (experiment)
Psychological Science 16 (1), 70–76

G. S. Halford, W. H. Wilson, & S. Phillips, (1998)
Processing capacity defined by relational complexity: Implications for comparative, developmental, and cognitive psychology (review article)
Behavioral and Brain Sciences, 21, 803–831.

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