Displaying Pete Trimmer.JPG



I am a behavioural ecologist.  I research the evolution of learning, decision-making and physiological processes, using a mix of analytical and computational techniques.  I am currently looking at how individual niche differences are supported by evolutionary processes.

Much of my work relates to the principles of understanding decision-making: exposing the evolutionary logic of how seemingly sub-optimal behaviour can make sense, and identifying conditions under which rational learning and decision-making would not evolve.  Whereas Niko Tinbergen identified that there are often four types of question in behavioural ecology, I often find there are often numerous possible answers to each of the questions!

My work has included showing why the placebo effect should evolve, modelling speed-accuracy trade-offs in mammals, identifying conditions under which economically rational (e.g., transitive) decisions would not be favoured by natural selection, modelling various state-dependent scenarios and showing impacts of state on learning, identifying conditions under which various biases (e.g., optimism) or traits (e.g., depression) are likely to emerge, showing that sub-optimal learning rules should evolve under particular conditions, modelling the co-evolution of bet-hedging traits (in both animals and plants), and showing that the well-known predictions of signal detection theory are misleading -- to the point of being reversed -- in many biological situations.  I summarise some of these studies and findings on the next page (here).

I've been very fortunate to work with great people; most notably Alasdair Houston & John McNamara (at Bristol, researching the evolution of mental mechanisms), Andy Sih (at UC Davis, looking at effects of rapid environmental change on behaviour) and am now working with Klaus Reinhold (at Bielefeld, Germany, looking at how individual differences can be supported by evolutionary processes).

If you have similar research interests or any questions, please drop me a line: 

pete.trimmer ['at'] gmail.com

+49 (0)1577 6219955

Peer-reviewed Publications

Trimmer, P.C., Houston, A.I., Marshall, J.A.R., Bogacz, R., Paul, E.S., Mendl, M.T., McNamara, J.M. (2008) Mammalian choices: combining fast-but-inaccurate and slow-but-accurate decision-making systems. Proc R Soc B 275(1649), 2353–2361.  (IF: 5.4)

McNamara, J.M., Trimmer, P.C., Eriksson, A., Marshall, J.A.R., Houston, A.I. (2010) Environmental variability can select for optimism or pessimism. Ecology Letters 14(1), 58-62.  (IF: 17.9)

Trimmer, P.C. (2010) The evolution of decision-making; various modelling approaches. University of Bristol; PhD thesis.

Trimmer, P.C., Houston, A.I., Marshall, J.A.R., Mendl, M.T., Paul, E.S., McNamara, J.M. (2011) Decision-making under uncertainty: biases and Bayesians. Animal Cognition 14(4), 465-476.  (IF: 2.8)

McNamara, J.M., Trimmer, P.C., Houston, A.I. (2012) The ecological rationality of state-dependent valuation. Psychological Review 119, 114-119.  (IF: 9.8)

Houston, A.I., Trimmer, P.C., Fawcett, T.W., Higginson, A.D., Marshall, J.A.R., McNamara, J.M. (2012) Is optimism optimal? Functional causes of apparent behavioural biases. Behavioural Processes 89, 172-178.  (IF: 1.5)

Trimmer, P.C., McNamara, J.M., Houston, A.I., Marshall, J.A.R. (2012) Does natural selection favour the Rescorla-Wagner rule? Journal of Theoretical Biology 302, 39-52.  (IF: 2.4)

Higginson, A.D., Fawcett, T.W., Trimmer, P.C., McNamara, J.M., Houston, A.I. (2012) Generalized optimal risk allocation: foraging and antipredator behavior in a fluctuating environment.  The American Naturalist 180(5), 589-603.  (IF: 4.7)

McNamara, J.M., Trimmer, P.C., Houston, A.I. (2012) It's optimal to be optimistic about survival.  Biology Letters 8, 516-519.  (IF: 3.3)

Trimmer, P.C., Marshall, J.A.R., Fromhage, L., McNamara, J.M., Houston, A.I. (2013) Understanding the placebo effect from an evolutionary perspectiveEvolution & Human Behaviour 34, 8-15.  (IF: 3.6)

Marshall, J.A.R., Trimmer, P.C., Houston, A.I., McNamara, J.M. (2013)  On evolutionary explanations of cognitive biasesTREE 28(8), 469-473.  (IF: 15.4)

Trimmer, P.C. (2013) Optimal behaviour can violate the principle of regularity. Proc R Soc B, 280(1763).  (IF: 5.4)

Marshall, J.A.R., Trimmer, P.C., Houston, A.I. (2013)  Unbiased individuals use valuable information when making decisions: a reply to Johnson & Fowler.  TREE 28(8), 444-445.  (IF: 15.4)

Trimmer, P.C., Paul, E.S., Mendl, M.T., McNamara, J.M., Houston, A.I. (2013) On the evolution and optimality of mood states. Behavioral Sciences 3, 501-521.  (No IF yet.)

McNamara, J.M., Trimmer, P.C., Houston, A.I. (2014) Natural selection can favour ‘irrational’ behaviourBiology Letters 10, 20130935.  (IF: 3.3)

Trimmer, P.C. & Houston, A.I. (2014) An evolutionary perspective on information processingTopics in Cognitive Science 6, 312-330.  (IF: 2.2)

Fawcett, T.W., Fallenstein, B., Higginson, A.D., Houston, A.I., Mallpress, D.E.W., Trimmer, P.C., McNamara, J.M. (2014) The evolution of decision rules in complex environmentsTrends in Cognitive Sciences 18(3), 153-161.  (IF: 16.0)

*Trimmer, P.C., Higginson, A.D., Fawcett, T.W., McNamara, J.M., Houston, A.I. (2015) Adaptive learning can result in a failure to profit from good conditions: implications for understanding depression. Evolution, Medicine, and Public Health. Vol 1, 123-135. (No IF yet.)  

[* Won the inaugural George C Williams prize unanimously, for 'most significant article' published by the journal.]

Trimmer, P.C. & Houston, A.I. (2016) The ups and downs of placebos. Book chapter in: (ed. R. Sear) Evolutionary Thinking in Medicine: From Research to Policy and PracticePart of the series Advances in the Evolutionary Analysis of Human Behaviour. Springer, 357-369.

English, S., Fawcett, T.W., Higginson, A.D., Trimmer, P.C., Uller, T. (2016)  Adaptive use of information during growth can explain long-term effects of early life experiences. The American Naturalist 187(5), 620-632. (IF: 4.7)

Sih, A., Trimmer, P.C., Ehlman, S.M. (2016) A conceptual framework for understanding behavioural responses to HIREC. Current Opinion in Behavioral Sciences 12, 109-114. 

Trimmer, P.C. (2016) Optimistic and realistic perspectives on cognitive biases. Current Opinion in Behavioral Sciences 12, 37-43.

Trimmer, P.C., Ehlman, S.M., Sih, A. (2017) Predicting behavioural responses to novel organisms: state-dependent detection theory. Proc R Soc B 284(1847), 20162108.  (IF: 5.4)

Trimmer, P.C., Ehlman, S.M., McNamara, J.M., Sih, A. (2017) The erroneous signals of detection theoryProc R Soc B 284(1865), 20171852.  (IF: 5.4)

Mobbs, D., Trimmer, P.C., Blumstein, D.T., Dayan, P. (2018) Foraging for foundations in decision neuroscience: Insights from ethology. Nature Reviews Neuroscience. doi:10.1038/s41583-018-0010-7  (IF: 28.9)

Crowley, P.H., Trimmer, P.C.Spiegel, O., Ehlman, S.M., Cuello, W.S., Sih, A. (accepted) Predicting habitat choice after rapid environmental change. The American Naturalist.

McNamara, J.M. & Trimmer, P.C. (2018) Sequential choices using signal detection theory can reverse classical predictionsBehavioral Ecology, ary132.

Cuello, W.S., Gremer, J.R., Trimmer, P.C., Sih, A., Schreiber, S.J. (accepted) Predicting evolutionarily stable strategies from functional trade-offs of Sonoran Desert annuals. Proc R Soc B.

Greggor, A., Trimmer, P.C., Barrett, B.J., Sih, A. (submitted) Predicting learning (or not) in response to environmental change.

Ehlman, S.M., Trimmer, P.C., Sih, A. (accepted)  Prey responses to exotic predators: effects of old risks and new cues.  The American Naturalist.

Trimmer, P.C., Barrett, B.J., McElreath, R., Sih, A. (submitted) Rapid environmental change in games: complications and counter-intuitive outcomes.

Trimmer, P.C., McNamara, J.M., Crowley, P.H., Gil, M., Sih, A. (in prep) A model of behavioral and physiological trade-offs.

Trimmer, P.C., Greggor, A., Barrett, B.J., Crowley, P.H., Stephens, D.W., Sih, A. (in prep) Effects of neophobia in a changing world. 

Crowley, P.H., Trimmer, P.C., Spiegel, O., Ehlman, S.M., Sih, A. (in prep) Habitat choice and rapid environmental change: mitigation by learning.

Tabor, A., McNamara, J.M., Trimmer, P.C., Houston, A.I. (in prep) The importance of internal uncertainty in human decision-making.

Crowley, P.H., Lopez, L., Trimmer, P.C., Todgham, A., Gil, M., Sih, A. Integrating physiological and behavioral responses to multiple stressors in changing environments.

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