Groups Decision Making: Dum is Over-weighted, Smart is Under-weighted, Of Course


Take Aways –

  • people tend to overestimate their own performance on hard tasks
  • paradoxically, when given an easy task, they tend to underestimate their own performance (the hard-easy effect)
  • when comparing themselves to others,
  • people with low competence tend to think they are as good as everyone else,
  • whereas people with high competence tend to think they are as bad as everyone else (the Dunning–Kruger effect)

Equality Bias Impairs Collective Decision-Making Across Cultures

Ali Mahmoodi, et al. PNAS March 24, 2015 vol. 112 no. 12 3835-3840

We tend to think that everyone deserves an equal say in a debate. This seemingly innocuous assumption can be damaging when we make decisions together as part of a group. To make optimal decisions, group members should weight their differing opinions according to how competent they are relative to one another; whenever they differ in competence, an equal weighting is suboptimal.

Replicated across three countries (Denmark, Iran, and China), we show that participants assigned nearly equal weights to each other’s opinions regardless of true differences in their competence—even when informed by explicit feedback about their competence gap or under monetary incentives to maximize collective accuracy. This equality bias, whereby people behave as if they are as good or as bad as their partner, is particularly costly for a group when a competence gap separates its members. Continue reading


Medieval Pathogen Loads


Medieval cesspit in Jerusalem reveals 15th century diseases

Analysis of a latrine in Jerusalem that dates back over 500 years finds human parasites common in northern Europe yet very rare in Middle East at the time, suggesting long-distance trade or pilgrimage routes and shedding light on prevalent infectious diseases of the age.

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New Book Project Launched: B3: “The Brain, Behavior and Business”


We are launching a new book project “The Brain, Behavior and Your Business.”   A brief description if below.  Ideas welcome.

Book Project Brief: “The Brain, Behavior and Your Business” (B3)
Applying the Best Brain Science to Business, Policy and Professional Problem Solving at Your Work

USP: Your one source for current and future best knowledge and practices in brain science applied to your professional work.

I.  Overview – The Professional’s Primer on the Brain and Behavior
You are very smart and already successful professional, senior leader and decision-maker. How you get better from here depends on knowing more than others – and more than you know now. Perhaps, a lot more. The winner is the one with the best information and there is no better information than the best brain science – but you need an expert source and guide. Continue reading

“…people with similar levels of competence make the best decision-making groups, as otherwise the tendency to assume equal competence can give undue weight to the opinions of less capable members.”