Monthly Archives: June 2015

Signal Detection for Categorical Decisions


erev2This post looks at signal detection theory (SDT) once again. Ken Hammond helped me see the power of signal detection as a descriptive theory (post Irreducible Uncertainty..) The last year of news with respect to fatal encounters between the police and the public has made me think of signal detection again as quite relevant. I should note that Ken Hammond died in May 2015 and I am looking for his last paper  “Concepts from Aeronautical Engineering Can Lead to Advances in Social Psychology”.  This post is based on a paper: “Signal Detection by Human Observers: A Cutoff Reinforcement Learning Model of Categorization Decisions Under Uncertainty,” written by Ido Erev that appeared in the Journal of the American Psychological Association, 1998, Vol. 105, No. 2, 280-298. This paper is important, but dated.

Many common activities involve binary categorization decisions under uncertainty. The police must try to distinguish between the individuals who can and want to harm the public and/or the police from others.  A doctor has to decide whether or not he should do more tests to see if you may have cancer. According to Erev, the frequent performance of categorization decisions and the observation that they can have high survival value suggest that the cognitive processes that determine these decisions should be simple and adaptive. Thus, it could be hypothesized that one basic (simple and adaptive) model can be used to describe these processes within a wide set of situations.

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Perceptual presence

affiche - pleine pageThis post joins several others in being only tangentially related to JDM. It is based on the paper: “The felt presence of other minds: predictive processing, counterfactual predictions, and mentalizing in autism,” that appears in 2015 Consciousness and Cognition. The authors are Colin J. Palmer, Anil K. Seth and Jakob Hohwy. (Post Prediction error minimization)

A central ingredient of social experience is that we represent the mental states of other people. This sense of others’ mental states is a part of our understanding and anticipation of their behavior, and molds our own behavior correspondingly. If our friend shows up to the restaurant with a grim face, we have a sense of her mood and adjust our greeting accordingly. If she glances at our empty glass while pouring herself some wine, we have a sense of her intentions and might move our glass closer. This is the concept of mentalizing.

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Neurons and decision making

neuron1This blog has included about a dozen posts that mention neurons so I have decided to mine them for the most noteworthy ideas. This was tougher than I thought it would be.

Fun facts about neurons that impact decisions

Relative judgments

Since neurons encode changes in stimulation (rather than absolute levels), absolute judgments on any dimension are much more difficult than relative judgments. This lies at the root of Ernst Weber’s 1834 observation that detectable increases in visual or auditory signal intensity are proportional to the starting value, i.e., need to be larger for larger starting values. (from post First Half of 2009 JDM Research Summary)


There is a hierarchy of neurons and there are a lot of them. So it is quite likely that I have a neuron dedicated to Salma Hayek, etc.


Neural responses are noisy.  As an example, a radiologist may have tumor detecting neurons. These hypothetical tumor detectors will give noisy and variable responses. After one glance at a scan of a healthy lung, our hypothetical tumor detectors might fire 10 spikes per second. After a different glance at the same scan and under the same conditions, these neurons might fire 40 spikes per second. (from post Signal Detection Theory)

Neuronal Recycling

In Reading in the Brain, Dehaene introduces the idea of “neuronal recycling” whereby portions of our ventral visual system are turned over to reading and writing.  He says that after centuries of trial and error, writing systems evolved to a form adapted to our brain circuits. (from post Toward a Culture of Neurons)

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