Development of Behavioral Stages in Animals


Michael Lamport Commons and Patrice Marie Miller


Jean Piaget was one of the first psychologists to propose stages of development in children.  Since then, a few researchers have written about stages of development in animals.  For example, Sue Taylor Parker and Michael McKinney wrote about stages in monkeys and apes.  One of the difficulties in comparing animals and humans, is that the traditional tasks used to test human behaviors cannot be directly applied to animals, nor can the tasks for one animal always be applied to another. 


The Model of Hierarchical Complexity Allows for Interspecies Comparisons


In recent years, Michael Lamport Commons and his colleagues have proposed the Model of Hierarchical Complexity (MHC) that can be used to determine the stages of animal behavior as well as human behavior.  It does so by taking the actions and tasks that animals and humans engage in, and putting them into an order based upon how hierarchically complex they are.  A task action is defined as more hierarchically complex when the higher order action is defined in terms of the actions at the next lower order and organizes these lower-order actions in a non-arbitrary way.  Thus, the order of hierarchical complexity is obtained by counting the number of coordinations that the action must perform on each lower order action until one reaches a set of elementary order actions.  If an action organizes two or more actions from an order before it, that organizing action is by definition one order higher and is therefore more hierarchically complex.  Stage of performance has the same name and number as the corresponding order of hierarchical complexity of the task it correctly completes.


Behavioral task actions have been described by fifteen hierarchical orders of complexity.  Theoretically, higher orders are possible.  Based on this theory, the table shows stages of animal behaviors.  An animal species is characterized by the highest stage of performance observed of any member of that species with any amount of training.  Animals have been observed to engage in actions up the concrete stage of development, which is about what 8 to 10 year old children do. 


        The barrier against animals developing abstract stage actions, which is the next stage beyond concrete, is great. At the concrete stage, action involves a small number of specific instances.  At the abstract stage, actions involve large to indefinite sized-sets.  There are no concrete instances for many of these indefinitely large sets and, for this reason, many of the sets are represented by variables.  The value of variables can refer to hypothetical things that do not exist.  Once one starts using variables it becomes essential to have abstract symbols, such as words, to label those variables.  Only humans, thus far, have shown the capacity for using such arbitrary symbols.


A comparison of animals stages



Order of Hierar-

chical Complexity


Name (Commons, et al 1998)




Examples of highest stage attained by a species                   








Exact-no generalization


For computers, only written programmed learning possible.  There are no animals that function at this stage.




Sensory & Motor


Rote, Generalized


When water moves, molluscs open shell.  Reflexively, if something touches membrane, shell close.  Mobile animals (e.g. Aplysia) habituate, sensitize, and classically and operantly condition.  Conditioning produces  generalizations about which stimuli will elicit the responses of interest




Circular Sensory-motor


Open-Ended Classes


Animals coordinate perception with action, or two or more actions.  Those whose hunting behavior is controlled by consequences (e.g. most predatory fish, insects) are in this stage.  Corrette (1990) observed prey capture in the praying mantis, which coordinated capture and strike movements.  Animals, whose hunting behavior is controlled by consequences (e.g. most predatory fish, insects) are also in this stage.








Concepts such as oddity learning in rats  (e.g. Bailey & Thomas 1998).  Rats discriminated the “odd” one when given two ping pong balls with food odors and one different order.






Relations among concepts.  Named concepts



Vaughan (1988) trained pigeons to associate two arbitrary subclasses of slides of trees with different response rates.  High response rate was associated with slides in one subclass and low response rate with slides of the other subclass.  When slides in the subclass previously associated with high response rate became associated with low response rate (and vice versa), the pigeons changed their associations and correctly responded to each slide after a short reacquisition trial, showing they could attach a virtual label to a subclass.






Imitates & acquires sequences. Follows short sequential acts


Pepperberg’s (1992) African Grey parrot Alex, uttered multi-word  sentences organizing nominal labels and words.  Alex counted two objects, “one, two”.  To the new question, “What matter [is this ] four corner blue [object made of] ?” Alex correctly responded, “wood”.  Dogs and cats run through long arbitrary sequences of actions. 






Simple deduction without contradiction  excluded. Follows lists of sequential acts


Brannon & Terrace (1999) trained Rhesus Monkeys to indicate the larger of two sets of 1 to 4 squares and circles in two rows.  Chimpanzees put nuts onto selected flat anvil stones, and cracked them with selected hammer stones (Inoue-Nakamura & Matsuzawa (1997).  Weir, Chappell & Kacelnik (2002) observed that New Caledonian crows make tools by bending a straight piece of wire and then use the wire to pull food out of a tube.  Hunt (1996, 2000) observed similar crow behavior in the wild.






Logical deduction and empirical rules.  True counting. Simple arithmetic


Washburn and Rumbaugh (1991) trained Rhesus monkeys to select Arabic numerals associated with a number of  food pellets.  They reliably choose the numeral associated with the larger number of food pellets in a random array of up to 5 numerals.  Rumbaugh, Hopkins, et al (1989) showed an adult female chimpanzee removing from a TV display the number of boxes appropriate to the value of a randomly selected Arabic numeral, 1, 2 or 3).








de Waal and Lanting (1997) describe Kanzi, a captive Bonobo chimpanzee, used sharp stone flakes and tested the sharpness of each flake with his lips, rejecting non-sharp ones.  He then made flakes by throwing a rock against a hard surface, producing many flakes at once.  Making simple flake tools is a primary order action  Testing the tools is another primary order action.  Coordinating one primary stage action with the another is a concrete stage action.  De Waal (1996) describes how a beta male chimpanzee broke up conflicts in an impartial manner.  In order to act impartially, the beta male had to consider the perspectives of the other chimps along with his own perspective.  While his awareness of each of these perspectives is a primary action, his ability to integrate all of these perspectives together demonstrates that he operates at the concrete.



General Informational References


                de Waal, F. B. M., & Lanting, F.  (1997). Bonobo: The forgotten ape.  Berkeley: University of California Press.


                Goodall, Jane (1988).  In the shadow of man (Revised edition).  Boston, MA: Houghton-Mifflin.


                Parker, S. T,. & McKinney, M. L. (2000).  Origins of intelligence: the evolution of cognitive development in monkeys, apes, and humans.  Baltimore: Johns Hopkins Press.


                Wadsworth, B.  J.  (1995).  Piaget’s theory of cognitive and affective development (Fifth edition).  New York: Longman. 


Specific References from Stage Table


Bailey, A.M., & Thomas, R. K. (1998). An investigation of oddity concept learning by rats. Psychological Record, 48, 333-344.


Brannon, E. M., & Terrace, H. S. (1998). Ordering of the numerosities 1 to 9 by monkeys. Science, 282, 746-749.


Chappell, J., & Kacelnik, A. (2002). Tool selectivity in a non-mammal, the New Caledonian crow (Corvus moneduloides). Animal Cognition, 5:71-78 DOI 10.1007/s10071-002-0130-2


Chappell, J. & Kacelnik, A. (in prep). Selection of tool diameter by New Caledonian crows Corvus moneduloides.


Corrette, B. J.  (1990).  Prey capture in the praying mantis tenodera-aridifolia-sinensis - coordination of the capture sequence and strike movements.  Journal of Experimental Biology 148, 34


                Commons, M. L., Trudeau, E. J., Stein S. A., Richards F. A., & Krause S. R.  (1998). Hierarchical complexity of tasks shows the existence of developmental stages.  Developmental Review, 18(3), 237-278.


de Waal, F. B. M. (1996). Good natured: The origins of right and wrong in humans and other animals.  Cambridge, MA: Harvard University Press, Cambridge, MA.


de Waal, F. B. M., & Lanting, F.  (1997). Bonobo: The forgotten ape.  Berkeley: University of California Press.


Inoue-Nakamura, N. & Matsuzawa, T.  (1997).  Development of stone tool use by wild chimpanzees (pan Troglodytes).  Journal of Comparative Psychology, 111 (2), 159-173.


Hunt, G. R. (1996).  Manufacture and use of hook-tools by New Caledonian crows.  Nature, 379, 249-251.


Hunt, G. R. (2000).  Human-like, population-level specialization in the manufacture of pandanus tools by New Caledonian crows Corvus moneduloides.  Proceedings of the Royal Society of London B, 267, 403-413.


Lebowitz, B., & Brown, M. F.  (1999).  Sex differences in spatial search and pattern learning in the rat.  Psychobiology. 27(3), 364-371.


Parker, S. T,. & McKinney, M. L. (2000).  Origins of intelligence: the evolution of cognitive development in monkeys, apes, and humans.  Baltimore: Johns Hopkins Press.


                Pepperberg, I.  (1992).  Proficient performance of a conjunctive, recursive task by an African gray parrot (Psittacus erithacus).  Journal of Comparative Psychology, 106(3), 295-305.


                Rumbaugh, D. M., Hopkins, W. D., Washburn, D. A., & Savage-Rumbaugh, E. S.  (1989).  Lana chimpanzee learns to count by "NUMATH": a summary of a videotaped experimental report.  Psychological Record, 39(4), 459-70.


Vaughan, W.  Formation of equivalence sets in pigeons. (1988).  Journal of Experimental Psychology-Animal Behavior Processes, 14(1), 36-42. 


Washburn, D.A., & Rumbaugh, D. M.  (1991).  Ordinal judgments of numerical symbols by macaques (Macaca mulatta). Psychological Science, 2(3), 190-193.


Weir, A. A. S., Chappell, J., & Kacelnik, A. (2002). Shaping of hooks in New Caledonian crows. Science, 297:981