David Lykken

The psychologist David Lykken has died at the age of 78 (New York Times obituary, 20 Sept). Many readers will have come across Lykken via his books The Anti-Social Personalities (1995), an analysis of psychopathic and sociopathic personalities and A Tremor in the Blood (2nd Edn, 1998), an examination of polygraphy. Lykken pioneered the development of the Guilty Knowledge Test, described here in Ben-Shakhar and Elaad (2002):

The GKT […] utilizes a series of multiple-choice questions, each having one relevant alternative (e.g., a feature of the crime under investigation) and several neutral (control) alternatives, chosen so that an innocent suspect would not be able to discriminate them from the relevant alternative […] Typically, if the suspect’s physiological responses to the relevant alternative are consistently larger than to the neutral alternatives, knowledge about the event (e.g., crime) is inferred. As long as information about the event has not leaked out, the probability that an innocent suspect would show consistently larger responses to the relevant than to the neutral alternatives depends only on the number of questions and the number of alternative answers per question. Thus, the rate of false-positive errors (innocent examinees classified as guilty) can be controlled such that maximal protection for the innocent is provided.

The GKT is generally acknowledged to have a strong scientific foundation, although it is difficult to apply in most criminal investigations. The key problem is that the “guilty knowledge” that the subject is being tested for cannot be something that an innocent person might have picked up, for instance, through publicity about the crime or leakage from investigating officers, or could have guessed (Paul Ekman has a good discussion of the strengths and limitations of the GKT in his chapter on the polygraph in Telling Lies [2001]).

But Lykken was also renowned for his work on the University of Minnesota twin study:

He and two University of Minnesota colleagues, Thomas Bouchard and Auke Tellegen, tracked down and reunited more than 130 twins and documented striking similarities in the pairs’ behavior and personal quirks. Some had been raised near each other in the same state but in different family environments; others had grown up in different countries. But their shared genetic inheritance trumped vast differences in their upbringing, the researchers found. The study, though not the first of its kind, was by far the largest and most convincing, and its impact was immediate, experts said.

“It showed that the genetic influence on human psychology was far more pervasive than people had assumed, that it pervaded not just traits like intelligence but also political affiliations, lifestyle choices, likelihood of divorce, even religiosity,” said Scott Lilienfeld, a psychologist at Emory University in Atlanta who studied under Dr. Lykken.

A fascinating and important life’s work.

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