Prof. Armando D. B. Machado

Armando D. B. Machado

Professor of Psychology
Coordinator of the Animal Learning and Behavior Laboratory
Universidade do Minho (Portugal)

Personal page:

Machado Lab:

List of publications (pdf)

Education: Ph.D in Psychology at Duke University.

Research interests: Principles of learning; Choice and behavioral variability; Behavioral processes underlying choice; Operant conditioning; Number and temporal discrimination; Developmental psychology; Evolutionary biology; History of psychology; Mathematical models of behavior and learning; Epistemology and philosophical aspects related to behaviorism.

Present positions: President, the Portuguese Association of Experimental Psychology ● Editorial Board: Journal of the Experimental Analysis of Behavior; Behavior and Philosophy; Animal Learning and Behavior; International Journal of Psychology and Psychological Therapy ● Board of Trustees, the Cambridge Center for Behavioral Studies.

Web resources on Professor Machado: Armando Machado online at PsyCrit: Attention to Intention: Fact or artifact? (critic to Lau, Rogers, Haggard, Passingham - 2008, with A. Smith) ( ● Armando Machado interviewes B.F. Skinner, First European Meeting on Experimental Analysis of Behavior,Belgium, 1983 (audio: ● Videolectures: Armando Machado’s SQAB Tutorial: Probability: Basic ideas, techniques, and applications (2003) (video:


(Mostly available at Professor Machado’s website:

(2009) Machado, A., Malheiro, M. T., & Erlhagen, W. Learning to time: A perspective. Journal of the Experimental Analysis of Behavior, Vol. 92, 423-458 (

(2009) Monteiro, T., Machado, A. Oscillations following periodic reinforcement. Behavioural Processes, Vol. 81, 170-188 (

(2009) Maia, S., Machado, A. Representations of time intervals in a double bissection task: Relative or absolute? Behavioural Processes, Vol. 81, 280-285 (

(2009) Oliveira, L., & Machado, A. Context effect in a temporal bissection task with the choice keys available during the sample. Behavioural Processes, Vol. 81, 286-292 (

(2009) Machado, A., Costa, A., Maia, S. Directional selection of response numerosity: An exploratory study. Revista Brasileira de Análise do Comportamento, Vol. 3, 259-278 (

(2008) Arantes, J., Machado, A. Context effects in a temporal discrimination task: Further tests of the Scalar Expectancy Theory and Learning-to-Time models. Journal of the Experimental Analysis of Behavior, Vol. 90, 33-51 (

(2008) Oliveira, L., Machado, A. The effect of sample duration and cue on a double temporal discrimination. Learning and Motivation, Vol. 39, 71-94 (

(2007) Machado, A., & Silva, F. Toward a richer view of the scientific method: the role of conceptual analysis. American Psychologist, Vol. 62, 671-681 (

(2007) Guilhardi, P., MacInnis, M., Church, R., Machado, A. Shifts in the psychophysical function in rats. Behavioural Processes, Vol. 75, 167-175 (

(2007) Machado, A., Rodrigues, P. The differentiation of response numerosities in the pigeon. Journal of the Experimental Analysis of Behaviour, Vol. 88, 153-178 (

(2007) Almeida, A., Arantes, J., Machado, A. Numerosity discrimination in preschool children. Journal of the Experimental Analysis of Behavior, Vol. 88, 339-354 (

(2006) Machado A., Arantes J., Further tests of the Scalar Expectancy Theory (SET) and the Learning-to-Time (LeT) model in a temporal bisection task, Behavioural Processes, Jun 1;72(3):195-206 (

(2006) Machado A, Vasconcelos M., Acquisition versus steady state in the time-left experiment, Behavioural Processes, Feb 28;71(2-3):172-87 (

(2005) Machado A, Pata P., Testing the scalar expectancy theory (SET) and the learning-to-time model (LeT) in a double bisection task, Learning and Behavior, Feb;33(1):111-22 (

(2005) Armando Machado, Experimental methods and conceptual confusion, International Journal of Comparative Psychology, vol. 18, n.1, pp.28-33 (

(2004) Machado, A. On behavior and philosophy. The ABA International Newsletter, Vol. 27, Nº3, 9-10 (

(2003) Machado, A. Lessons from the "Problem of Points". The ABA Newsletter, Vol. 26, Nº.2, 36-37 (

(2003) Machado A, Keen R., Temporal discrimination in a long operant chamber, Behavioural Processes, Apr 28;62 (1-3):157-182 (

(2003) Armando Machado and Francisco J. Silva, You can lead an ape to a tool, but ...: A review of povinelli'sfolk. Physics for apes: the chimpanzee's theory of how the World works, Journal of the Experimental Analysis of Behavior, 79,267-286 number 2 (march) (

(2002) Machado A, Keen R., Relative numerosity discrimination in the pigeon: Further tests of the linear-exponential-ratio model, Behavioural Processes, Apr 28;57(2-3):131-148 (

(2002) Machado, A. Mathematics, concepts, and data. The ABA Newsletter, Vol. 25, Nº3, 27 (,%20concepts,%20and%20data.pdf)

(2002) Machado, A., Silva, F.J. Animal Learning. Encyclopedia of Cognitive Science. London, UK: Macmillan (

(2000) Armando Machado, Orlando Lourenço, Francisco J. Silva, Facts, concepts, and theories: The shape of psychology's epistemic triangle,Behavior and Philosophy, 28, 1- 40 (

(2000) Armando Machado and Paulo Guilhardi, Shifts in the psychometric function and their implications for models of timing, Journal of the Experimental Analysis of Behavior, 74, 25-54, 1 (July) (

(1999) Machado, A., Keen, R. Learning to time (LeT) or scalar expectancy theory (SET)? A critical test of two models of timing. Psychological Science, Vol. 10, Nº3, 285-290 (

(1999) Keen, R., Machado, A. How pigeons discriminate the relative frequency of events. Journal of the Experimental Analysis of Behaviour, Vol. 72, 151-175 (

(1999) Lourenço, O., Machado, A. Rich conversation but vague theory. Developmental Science, Vol. 2, Issue 1, 21-23 (

(1999) Armando Machado and Richard Keen, The learning of response patterns in choice situations, Animal Learning & Behavior, 27 (3), 251-271 (

(1999) Armando Machado, Of minds, brains, and behavior - A review of Uttal's (1998) "Toward a new behaviorism: The case against perceptual reductionism", Behavior and Philosophy, 27, 51-74 (

(1998) Armando Machado and Francisco J. Silva, Greatness and misery in the teaching of the psychology of learning, Journal of the Experimental Analysis of Behavior, 70,215-234 number 2 (September) (

(1998) Machado, A., Cevik, M. Acquisition and extinction under periodic reinforcement. Behavioural Processes, Vol. 44, 237-262 (

(1997) Machado, A., Learning the temporal dynamics of behavior. Psychological Review, Vol. 104, Nº2, 241-265 (

(1997) Armando Machado, Increasing the variability of response sequences in pigeons by adjusting the frequency of switching between two keys, Journal of the Experimental Analysis of Behavior, 68, 1-25 number 1 (July) (

(1997) Armando Machado and Munire Cevik, The discrimination of relative frequency by pigeons, Journal of the Experimental Analysis of Behavior, 67, 11-41 number 1 (January) (

(1996) Orlando Lourenqo, Armando Machado, In defense of Piaget's Theory: A reply to 10 common criticisms, Psychological Review, Vol. 103, No. I, 143-164 (

(1994) Armando Machado, Polymorphic response patterns under frequency-dependent selection, Animal Learning & Behavior, 22 (1), 53-71(

(1993) Armando Machado, Internal states: Necessary but not sufficient, Journal of the Experimental Analysis of Behavior, Sep; 60(2):469-472 (

(1993) Machado, A. Learning variable and stereotypical sequences of responses: Some data and a new model. Behavioural Processes, Vol. 30, 103-130 (

(1993) Davis, D. G. S., Staddon, J. E. R., Machado, A., & Palmer, R. G, The process of recurrent choice, Psychological Review, vol. 100, pp. 320-341 (

(1992) Machado, A. Behavioral variability and frequency-dependent selection. Journal of the Experimental Analysis of Behaviour, Vol. 58, 241-263 (

(1989) Machado, A. Operant conditioning of behavioral variability using a percentile reinforcement schedule. Journal of the Experimental Analysis of Behaviour, Vol. 52, 155-166 (

Updated: January 30, 2010

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