Klaus Fiedler: In Memoriam

In memory of a brilliant scholar, and generous and kind person, who passed away on May 14, 2026.

Klaus Fiedler, a sampling man

Joachim Krueger, Brown University

5/18/2026

Klaus Fiedler understood the limitations of human life and thus the limitations of our psychology, our modest efforts to understand what’s going on. When I met Klaus around the year 2000 he had moved from his research on language to research on judgment and decision-making. He was in the process of staking out a new terrain, an achievement that deserves the label of paradigm shift. Klaus understood that in a complex world we won’t see the whole, but must do with samples. The nature of these samples is our psychological ecology. Our thinking, judging, and choosing depend on it. From this insight, Klaus derived the conclusion that what to many conventional psychologists looks like human error may be sufficiently explained by biases built into the available samples. Of course, Klaus also understood that genuine psychological fallacies can sit on top of biased sampling input, and he turned his attention to what he called “metacognitive myopia.”

Klaus drew inspiration from the yin of rigorous deductive reasoning and the yang of clean experimental inductive work. Many of his empirical results were not surprising counterintuitive discoveries of the whiz-bang variety, but demonstrations of painstakingly excavated truths implied by strong theories based on firm first principles. This dialectical recognition of the integrated upward and downward flow of insight and inference marked his work. Incidentally, this outlook explains why Klaus had little patience for the moaning and chest-beating of those who spend their careers riding the replication-crisis train. Klaus saw that the replication industry was theoretically barren and judgmentally biased against positive results (Fiedler, Kutzner, & Krueger, 2012).

I had occasion to work with Klaus on a paper questioning Bem’s ballyhoo’d precognition research (Fiedler & Krueger, 2013). We argued that Bem’s results had to be considered false lest we are prepared to re-write the axioms of theoretical physics. Failing to replicate Bem’s results empirically was a waste and beside the point. Some things – like Bem’s claims – cannot be so, whereas other things, interesting things, “must be so”, as Klaus loved to insist. One such thing is the regression effect, a perennial monstrous presence in the empirical literature, which Klaus and I argued is more than a statistical necessity. We may look at regression as an artifact, but we can also meditate on its theoretical power and inspirational value. Many strong theoretical claims and empirical findings can be harvested from it (Fiedler & Krueger, 2012).

Sitting with Klaus in his office – the door of which was always open – was a stress test. His speech acts, as he would humorously call his words from time to time – were delivered with intention and intensity. His mind moved fast, and he occasionally lost track of how far behind you were, listening to him, trying to comprehend his meaning, and seeking to prepare a rational and respectable response. It was work. And it was rewarding in the end. Just how much you had learned from Klaus in a few minutes would often take days to percolate before it could turn into recognition and then gratitude.

Klaus loved those he had admitted to his inner circle. He was a gracious host in his home, serving dinner on the rooftop or treating you in a rustic half-timber restaurant in his hometown of Weinheim. I recall my rite of passage requiring the enjoyment of a Palatinate Sow’s Stomach. Klaus would pick the wine. He knew his wine, especially the local varieties from Rheinhessen and the Palatinate. He took me once to his favorite vineyard on the Rhine’s rive gauche. We drove in his VW convertible, Klausens blond hair blowing in the wind. I remember seeing a man who was happy. At the vineyard he chatted with the owner, a man he knew well, and he introduced me to some of the secrets of a proper tasting.

Klaus taught high theory, and he also taught by example – or should we say “by sample?” The expedition to the vineyard showed me how it is done. A few weeks later, my daughter Lauren (who met Klaus years later at a conference in Ascona) came to visit me in Heidelberg, where I was spending the summer as Klausens guest. I took Lauren to the wine region of the Palatinate, and we sampled the vintages, just like Klaus had shown. A successful replication.

My last memory of Klaus dates from July, 2025. We both attended a conference convened by Joe Forgas outside of Budapest. The topic was the psychology of trust. Klaus gave his take on the issue and complained that some of us had failed to drill to the theoretically sufficient core of the matter. We were still hewing to moralistic reasoning and our writing was geared more towards the life-style section of the weekend paper than towards the pages of the Journal of Experimental Psychology. That stung. We argued. We ran out of time before we could settle things. I felt frustrated. After dinner, I was sitting with some colleagues by the pool, sipping drafts of Dreher beer. Klaus emerged out of nowhere, flashed a radiant and friendly smile, and asked who was in the mood for a bottle of wine. I miss him.

Fiedler, K., Kutzner, F., & Krueger, J. I. (2012). The long way from a-control to validity proper: Problems with a short-sighted false-positive debate. Perspectives on Psychological Science, 7, 661-669. doi: 10.1177/1745691612462587

Fiedler, K. & Krueger, J. I. (2012). More than an artifact: Regression as a theoretical construct. In J. I. Krueger (Ed.). Social judgment and decision-making (pp. 171-189). Psychology Press.

Fiedler, K. & Krueger, J. I. (2013). Afterthoughts on precognition: No cogent evidence for anomalous influences of consequent events on preceding cognition. Theory & Psychology, 23, 323-333. doi: 10.1177/0959354313485504

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In Sadness and Honor

Joe Forgas

It is with great sadness and sorrow that I heard of the untimely passing of my great friend and colleague, Klaus Fiedler. He was one of the best known and most respected psychologists of his generation in Germany, with an impressive record of scientific publications, citations and prizes. Beyond his scientific achievements, Klaus has also been what in earlier times would be called a thoroughly ‘good man’, in every sense of the word. He was decent, generous, highly intelligent, devoted to science and unconditionally supportive of his colleagues, especially the younger ones.

We have been friends since 1982 when I met Klaus as a young faculty member at the University of Giessen where I just arrived. I was immediately struck by his kindness and generosity, and during many shared lunch discussions at the Mensa, by his encyclopaedic knowledge of psychology, methodology and epistemology, and his unconditional commitment to open discussion and the advancement of science.

We remained close friends ever since, and after he moved to Heidelberg, I spent several sabbaticals visiting his laboratory, and he also visited my group in Sydney. Most of my graduate students also visited Klaus in Heidelberg, and I was fortunate enough to welcome in my lab several of Klaus’ excellent students and colleagues like Christian Unkelbach and Alex Koch.

Klaus was that rare phenomenon, an unconditionally positive and optimistic person who saw the good side of everything and everyone, never complained, and dismissed misfortunes with a wave of his hand as insignificant details of an otherwise wonderful world where knowledge and decency are bound to triumph.

As a person, Klaus was uncommonly generous with his time and support for generations of young researchers. My own children who knew him for most of their lives loved him as a favourite uncle, a wonderful companion who was always ready to help. His devoted wife Michaela Waenke, psychology professor at Mannheim, was the love of his life, and the years they spent together were certainly Klaus’ happiest years.

His passing is a tragedy not only for his friends and family, including his two daughters, Ina and Eva, but also for all of us who retain an optimistic view about our civilisational values and especially the wonderful contribution that science can make to human flourishing. Klaus was one of the most consistent, clear-sighted and consequential defenders of open debate and scientific values, and an unfailing critic of our all-too-human failures that contribute to paradigmatic myopia and methodological lapses. He enriched our lives and our discipline both as a friend and as a scientist, and he will be sorely missed by all of us who were fortunate enough to know him. Rest in peace, my dear friend Klaus.