How psychology helped locate HMAS Sydney II, lost for over 60 years

The next time an ignoramus asks you what psychology has ever achieved, here's a new answer for you: it only helped in the 2008 discovery of the Australian light cruiser HMAS Sydney II, lost in deep water off the west coast of Australia since its sinking in November 1941.

John Dunn and Kim Kirsner have documented in a new paper how they used insights from research into memory transmission to analyse the testimony from the German survivors of the ship, HSK Kormoran, that battled with Sydney not long before both vessels were lost. Whereas, tragically, all the crew of Sydney perished, 317 of the German crew survived and many were interrogated by Australian authorities about what happened. Finding Kormoran was the key that would unlock the location of Sydney, as the ships were proximate at the time of their sinking.

Dunn and Kirsner applied many principles from cognitive psychology to the testimony provided by the German survivors, which included 72 references to the last known location of Kormoran, many of them contradictory. One of these principles is that as memory becomes degraded, either over time in an individual, or through transmission from one person to another - it becomes progressively influenced by a person's top-down expectations and expertise. Consider a study in which participants were asked to recall pictures of fruit and veg, some portrayed larger, some smaller, than their real-life sizes. People's memories for the pictures were distorted in the direction of prior knowledge, so that large vegetables were recalled as having been portrayed as larger.

Based on this idea, and with reference to the status and opportunity of the various witnesses, Dunn and Kirsner identified seven "source statements" about the location of Kormoran which had informed the testimony of the other witnesses and been (further) distorted by them. For example, one of the statements, now known to be inaccurate, was from the Kormoran captain Theodor Detmers.

To confirm this assessment of the available data, the researchers exploited techniques used in the analysis of species evolution, to identify clusters of statements, with each cluster containing statements of various levels of degradation or "mutation" from the key source statements. Once the source statements were confirmed, the researchers tested candidate locations for Kormoran and worked out the potential of each one in relation to its distance from the seven source statements.

A key facet of Dunn and Kirsner's approach was to use all the available testimony to arrive at a prediction of where Kormoran would be found. By contrast, other non-psychological experts involved in the search had tended to rely on just one or two key witnesses, such as Detmers.

By combining the best fit approach from the seven source statements with two further physical landmarks - drift objects lost from Kormoran and an emergency signal sent by Kormoran just prior to battle - Dunn and Kirsner identified a recommended search area. On 16 March 2008, the Finding Sydney Foundation located Kormoran just 5km from Dunn and Kirsner's best prediction of where she lay. Five days later, Sydney was found 21km away. The discovery helped heal a scar in Australia's history.

"The method we developed in response to the problem that was placed before us was necessarily tailored to the specific details of that problem," the researchers said. "Nevertheless, it may provide a blueprint for potential solutions to other similar problems. Such problems may include, but would not necessarily be restricted to, search problems for missing objects. In our view, the critical feature of a problem that would make it suitable for our methodology would be a set of statements or similar data that can be regarded as a set of constraints on a state of affairs that can be evaluated quantitatively. For example, and to move away from the present spatial domain, a relevant problem may involve the evaluation of eyewitness descriptions of a particular person, e.g. a criminal."
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Dunn, J., and Kirsner, K. (2011). The search for HMAS Sydney II: Analysis and integration of survivor reports. Applied Cognitive Psychology, 25 (4), 513-527 DOI: 10.1002/acp.1735

Post written by Christian Jarrett for the BPS Research Digest.

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