Journal Articles

PubMed versions of papers are available and in some cases full articles. Please contact us for PDF reprints of any of these papers.

(Student authors in boldface):

Haseltine, E. L., & Beran, M. J. (2024). Maze runners: Monkeys show restricted Arabic numeral summation during computerized two-arm maze performance. Animal Cognition, 27, 23.

Beran, M. J. (2023). I am as fooled as you are, say some primates…but only sometimes. Journal of Comparative Psychology, 137, 77-79. NCBI Logo

Beran, M. J. (2023). I’ll (not) take that: The reverse-reward contingency task as a test of self-control and inhibition. Learning and Behavior, 51, 9-14. NCBI Logo

Beran, M. J. (2023). Why do distractions sometimes aid self-control? Pigeons (Columba livia) highlight possible mechanisms underlying the distraction effects. Journal of Comparative Psychology, 137, 77-79.

Beran, M. J. (2023). Congratulations to Animal Cognition on its 50th birthday! Some thoughts on the last 50 years of animal cognition research. Animal Cognition, 26, 13-23. NCBI Logo

Beran, M. J., & Parrish, A. E. (2023). Consistently inconsistent perceptual illusions in nonhuman primates: The importance of individual differences. Animals, 13, 22.  https://doi.org/10.3390/ani13010022.  Full text

Flessert, M., Taubert, J., & Beran, M. J. (2023). Assessing the perception of face pareidolia in children (Homo sapiens), rhesus monkeys (Macaca mulatta) and capuchin monkeys (Sapajus apella). Journal of Comparative Psychology, 137, 90-101. NCBI Logo

Kelly, A. J., Camden, A. A., Williams, M. C., Beran, M. J., & Perdue, B. M. (2023). Habitual prospective memory in preschool children. PLoS One, 18, e0293599. Full text

Kelly, A. J., Williams, M. C., Parrish, A. E., Perdue, B. M., Little, S., & Beran, M. J. (2023). Focality and prospective memory in preschool children. Journal of General Psychology, 150, 234-251. NCBI Logo

Englund, M. D., & Beran, M. J. (2022). No evidence of the choice overload effect in a computerized paradigm with rhesus macaques (Macaca mulatta) and capuchin monkeys (Sapajus apella). Behavioural Processes, 194, 104545. NCBI Logo

Englund, M. D., Whitham, W., Conway, C. M., Beran, M. J., & Washburn, D. A. (2022). Nonhuman primates learn adjacent dependencies but fail to learn nonadjacent dependencies in a statistical learning task with a salient cue. Learning and Behavior, 50, 242-253. NCBI Logo

Beran, M. J., & Parrish, A. E. (2021). Nonhuman primate token use shows possibilities but also limitations for establishing a form of currency. Philosophical Transactions of the Royal Society B, 376, 20190675. NCBI Logo

Bryer, M. A. H., Koopman, S. E., Cantlon, J. F., Piantadosi, S. T., MacLean, E. L., Baker, J. M., Beran, M. J., Jones, S. M., Jordan, K. E., Mahamane, S., Nieder, A., Perdue, B. M., Range, F., Stevens, J. R., Tomonaga, M., Ujfalussy, D. J., & Vonk, J. (2021). The evolution of quantitative sensitivity. Philosophical Transactions of the Royal Society B, 377, 20200529. Full text.

Gurgand, L., & Beran, M. J. (2021). Assessing consistency in children’s and monkeys’ performance across computerized and manual detour problem tasks. Behavioural Processes, 182, 104291. NCBI Logo

Heimbauer, L. A., Beran, M. J., & Owren, M. J. (2021). A chimpanzee recognizes varied acoustical versions of sine-wave and noise-vocoded speech. Animal Cognition, 24, 843-854. NCBI Logo

James, B. T. (2021). Looking back to look forward: Avenues into the field of comparative psychology. Journal of Comparative Psychology, 135, 283-285.

James, B. T., Parrish, A. E, Guild, A. S., Creamer, C., Kelly, V., Perdue, B. M., Kelly, A. J., & Beran, M. J. (2021). Go if you know: Preschool children’s movements reflect their metacognitive monitoring. Cognitive Development, 17, 101001.

Kelly, A. J., & Beran, M. J. (2021). Multi-trial free recall dynamics in preschool children and young adults. Journal of Cognitive Psychology, 33, 837-852.

Parrish, A. E., & Beran, M. J. (2021). Children and monkeys overestimate the size of high-contrast stimuli. Attention, Perception, & Psychophysics, 83, 2123-2135. NCBI Logo

Smith, , J. D., Church, B. A., Jackson, B. N., Adamczyk, M. N., Shaw, C. N., & Beran, M. J. (2021). Launch! Self-agency as a discriminative cue for humans (Homo sapiens) and monkeys (Macaca mulatta). Journal of Experimental Psychology: General, 150, 1901-1917.

Addessi, E., Bourgeois-Gironde, S., Beran, M. J., Brosnan, S. F., & Leca, J-B. (2020). Are the roots of human economic systems shared with non-human primates? Neuroscience and Biobehavioral Reviews, 109, 1-15. NCBI Logo

James, B. T., Webster, M. F., Menzel, C. R., Whitham, W., & Beran, M. J. (2020). Post-event misinformation effects in a language-trained chimpanzee (Pan troglodytes). Animal Cognition, 23, 861-869. NCBI Logo

Krause, M., & Beran, M. J. (2020). Words matter: Reflections on language projects with chimpanzees and their implications. American Journal of Primatology, 82, e23187.

ManyPrimates, Altschul, D. M., Beran, M. J., Bohn, M., Caspar, K. R., Fichtel, C., Forsterling, M., Grebe, N. M., Hernandez-Aguilar, N. M., Kwok, S. C., Llorente, M., Motes-Rodrigo, A., Proctor, D., Sanchez-Amaro, A., Simpson, E. A., Szabelska, A., Taylor, D., van der Mescht, J., Volter, C. J., & Watzel, J. (2020). Collaborative open science as a way to reproducibility and new insights in primate cognition research. Japanese Psychological Review, 62, 205-220. Full text.

Parrish, A. E., French, K. A., Guild, A. S., Creamer, C. L., Rossettie, M S., & Beran, M. J. (2020). The density bias: Capuchin monkeys (Sapajus apella) prefer densely arranged items in a food-choice task. Journal of Comparative Psychology, 134, 232-240. NCBI Logo

Smith, T. R., & Beran, M. J. (2020). Outcome expectancy and suboptimal risky choice in nonhuman primates. Learning & Behavior, 48, 301-321. NCBI Logo

Smith, T. R., Parrish, A. E., Creamer, C., Rossettie, M., & Beran, M. J. (2020). Capuchin monkeys (sometimes) go when they know: Confidence movements in Sapajus apella. Cognition, 199. 104237. NCBI Logo

Agrillo, C., Beran, M. J., & Parrish, A. E. (2019). Exploring the Jastrow illusion in humans (Homo sapiens), rhesus monkeys (Macaca mulatta) and capuchin monkeys (Sapajus apella). Perception, 48, 367-385. NCBI Logo

Beran, M. J., French, K., Smith, T. R., & Parrish, A. E. (2019). Limited evidence of number-space mapping in rhesus monkeys (Macaca mulatta) and capuchin monkeys (Sapajus apella). Journal of Comparative Psychology, 133, 281-293. NCBI Logo

Church, B. S., Jackson, B. N., Beran, M. J., & Smith, J. D. (2019). Simultaneous vs. prospective/retrospective uncertainty monitoring: The effect of response competition across cognitive levels. Journal of Experimental Psychology: Animal Learning and Cognition, 45, 311-321. NCBI Logo

Many Primates, Altschul, D. M., Beran, M. J., Bohn, M., Call, J., DeTroy, S., Duguid, S. J., et al. (2019). Establishing an infrastructure for collaboration in primate cognition research. PLoS ONE, 14, e0223675. Click here for full paper.

Parrish, A. E., Beran, M. J., & Agrillo, C. (2019). Linear numerosity illusions in capuchin monkeys (Sapajus apella), rhesus macaques (Macaca mulatta), and humans (Homo sapiens). Animal Cognition, 22, 883-895. NCBI Logo

Beran, M. J. (2018). Monkey memory: Rehearsal emerges for novel images when familiarity cues fade. Current Biology, 28, R1399-R1400.

Beran, M. J. (2018). Replication and pre-registration in comparative psychology. International Journal of Comparative Psychology, 31Click here for the full paper.

Beran, M. J., & Hopkins, W. D. (2018). Self-control in chimpanzees relates to general intelligence. Current Biology, 28, 574-579. NCBI Logo

Boomer, J., Church, B. A., Zakrzewski, A. C., Beran, M. J., Baum, M. L., & Smith, J. D. (2018). I scan, therefore I decline: The time course of difficulty monitoring in humans (Homo sapiens) and macaques (Macaca mulatta). Journal of Comparative Psychology, 132, 152-165. NCBI Logo

French, K., Beran, M. J., Espy, K., & Washburn, D. A. (2018). Simians in the Shape School: A comparative study of executive attention. Learning & Behavior, 46, 281-293. NCBI Logo

Heimbauer, L. A., Beran, M. J., & Owren, M. J. (2018). A chimpanzee’s (Pan troglodytes) perception of variations in speech: Identification of familiar words when whispered and when spoken by a variety of talkers. International Journal of Comparative Psychology, 31Click here for the full paper.

Heimbauer, L. A., Conway, C. M., Christiansen, M. H., Beran, M. J., & Owren, M. J. (2018). Visual artificial grammar learning by rhesus macaques (Macaca mulatta): Exploring the role of grammar complexity and sequence length. Animal Cognition, 21, 267-284. NCBI Logo

Hoffman, M. L., Beran, M. J., & Washburn, D. A. (2018). Rhesus monkeys (Macaca mulatta) remember agency information from past events and integrate this knowledge with spatial and temporal features in working memory. Animal Cognition, 21, 137-153. NCBI Logo

Kelly, A. J., Perdue, B. M., Love, M. W., Parrish, A. E., & Beran, M. J. (2018). An investigation of prospective memory with output monitoring in preschool children. American Journal of Psychology, 133, 201-210. NCBI Logo

Miletto Petrazzini, M. E., Parrish, A. E., Beran, M. J., & Agrillo, C. (2018). Exploring the Solitaire illusion in guppies (Poecilia reticulata). Journal of Comparative Psychology, 132, 48-57. NCBI Logo

Parrish, A. E., Afrifa, E. A., & Beran, M. J. (2018). Exploring decoy effects on computerized task preferences in rhesus monkeys (Macaca mulatta). Animal Behavior & Cognition, 5, 235-253. Click here for the full paper.

Parrish, A. E., James, B. T., Rossettie, M. S., Smith, T. R., Otalora-Garcia, A., & Beran, M. J. (2018). Investigating the depletion effect: Self-control does not waiver in capuchin monkeys. Animal Behavior and Cognition, 118-138. Click here for the full paper.

Parrish, A. E., Perdue, B. M., Kelly, A. J., & Beran, M. J. (2018). Working memory in children assessed with serial chaining and Simon tasks. Behavioural Processes, 157, 528-531. NCBI Logo

Perdue, B. M., Beran, M. J., & Washburn, D. A. (2018). A computerized testing system for primates: Cognition, welfare, and the Rumbaughx. Behavioural Processes, 156, 37-50. NCBI Logo

Perdue, B. M., Evans, T. A., & Beran, M. J. (2018). Chimpanzees show some evidence of selectively acquiring information by using tools, making inferences, and evaluating possible outcomes. PLoS ONE, 13, e0193229. Click here for the full paper.

Perdue, B. M., Kelly, A. J., & Beran, M. J. (2018). Assessing distinctiveness effects and “false memories” in chimpanzees (Pan troglodytes)International Journal of Comparative Psychology, 31Click here for the full paper.

Smith, T. R., & Beran, M. J. (2018). Task switching in rhesus macaques (Macaca mulatta) and tufted capuchin monkeys (Cebus apella) during computerized categorization tasks. Journal of Experimental Psychology: Animal Learning and Cognition, 44, 229-246. NCBI Logo

Smith, T. R., Smith, J. D., & Beran, M. J. (2018). Not knowing what one knows: A meaningful failure of metacognition in capuchin monkeys. Animal Behavior and Cognition, 5, 55-67. Click here for the full paper.

Whitham, W., Johnson, J., French, K., Beran, M. J., & Washburn, D. A. (2018). Does joystick training facilitate relational learning? International Journal of Comparative Psychology, 31Click here for the full paper.

Beran, M. J. (2017). To err is (not only) human: Fallibility as a window into primate cognition.  Comparative Cognition & Behavior Reviews, 12, 57-81. Click here for the full paper.

Beran, M., & Parrish, A. (2017). The number sense is neither last resort nor of primary import. Behavioral and Brain Sciences, 40. doi:10.1017/S0140525X16002065

Beran, M. J., Perdue, B. M., Kelly, A. K., & Parrish, A. E. (2017). What’s in a face (made of foods)? Comparing children’s and monkeys’ perception of faces in face-like images of food. Animal Behavior and Cognition, 4, 324-339. Click here for full paper.

Brosnan, S. F., Price, S. A., Leverett, K., Prétôt, L., Beran, M. J., & Wilson, B. J. (2017). Human and monkey responses in a symmetric game of conflict with asymmetric equilibria. Journal of Economic Behavior & Organization, 142, 293-306.

Parrish, A. E., James, B. J., & Beran, M. J. (2017). Exploring whether nonhuman primates show a bias to overestimate dense quantities. Journal of Comparative Psychology, 131, 59-68. NCBI Logo

Parrish, A. E., Otalora-Garcia, A., & Beran, M. J. (2017). Dealing with interference: Chimpanzees respond to conflicting cues in a food-choice memory task. Journal of Experimental Psychology: Animal Learning and Cognition, 43, 366-376. NCBI Logo

Smith, T. R., Beran, M. J., & Young, M. E. (2017). Gambling in rhesus macaques (Macaca mulatta): The effects of cues signaling risky choice outcomes. Learning & Behavior, 45, 288-299. NCBI Logo

Agrillo, C., Parrish, A. E., & Beran, M. J. (2016). How illusory is the Solitaire illusion? Assessing the degree of misperception of numerosity in adult humans. Frontiers in Psychology, 7,1663. doi: 10.3389/fpsyg.2016.01663. Click here for a PDF file of this paper.

Beran, M. J. (2016). “Zeroing” in on mathematics in the monkey brain. Learning & Behavior, 44, 4-6. NCBI Logo

Beran, M. J., Hopper, L. M., de Waal, F. B. M., Brosnan, S. F., & Sayers, K. (2016). Chimpanzees, cooking, and a more comparative psychology. Learning & Behavior, 44, 103-108. NCBI Logo

Beran, M. J., Hopper, L. M., de Waal, F. B. M., Sayers, K., & Brosnan, S. F. (2016). Chimpanzee food preferences, associative learning, and the origins of cooking. Learning & Behavior, 44, 118-121. NCBI Logo

Beran, M. J., James, B. T., Whitham, W., & Parrish, A. E. (2016). Chimpanzees can point to smaller amounts of food to accumulate larger amounts but they still fail the reverse-reward contingency task. Journal of Experimental Psychology: Animal Learning and Cognition, 42, 347-358.NCBI Logo

Beran, M. J., Menzel, C. R., Parrish, A. E., Perdue, B. M., Sayers, K., Smith, J. D., & Washburn, J. D. (2016). Primate cognition: Attention, episodic memory, prospective memory, self-control, and metacognition as examples of cognitive control in nonhuman primates. WIREs Cognitive Science.  doi: 10.1002/wcs.1397 NCBI Logo

Beran, M. J., & Parrish, A. E. (2016). Capuchin monkeys (Cebus apella) treat small and large numbers of items similarly during a relative quantity judgment task. Psychonomic Bulletin & Review, 23, 1206-1213.NCBI Logo

Beran, M. J., Perdue, B. M., Church, B. A., & Smith, J. D. (2016). Capuchin monkeys (Cebus apella) modulate their use of an uncertainty response depending on risk. Journal of Experimental Psychology: Animal Learning and Cognition, 42, 32-43.NCBI Logo

Beran, M. J., Perdue, B. M., Rossettie, M. S., James, B. T., Whitham, W., Walker, B., Futch, S. E., & Parrish, A. E. (2016). Self-control assessments of capuchin monkeys with the rotating tray task and the accumulation task.  Behavioural Processes, 129, 68-79.  NCBI Logo

Beran, M. J., Rossettie, M. S., & Parrish, A. E. (2016). Trading up: Chimpanzees (Pan troglodytes) show self-control through their exchange behavior. Animal Cognition, 19, 109-121. NCBI Logo

Parrish, A. E., Agrillo, C., Perdue, B. M., & Beran, M. J. (2016). The elusive illusion: Do children (Homo sapiens) and capuchin monkeys (Cebus apella) see the Solitaire illusion? Journal of Experimental Child Psychology, 142, 83-95. NCBI Logo

Parrish, A. E., Emerson, I. D., Rossettie, M. S., & Beran, M. J. (2016). Testing the ego-depletion hypothesis among capuchin monkeys: Does glucose boost self-control? Behavioral Sciences, 6, 16. Click here for full-text of the paper.

Agrillo, C., Gori, S., & Beran, M. J. (2015). Do rhesus monkeys (Macaca mulatta) perceive illusory motion? Animal Cognition, 18, 895-910. NCBI Logo

Beran, M. J. (2015). Chimpanzee cognitive control. Current Directions in Psychological Science, 24, 352-357. NCBI Logo

Beran, M. J. (2015). The comparative science of “self-control”: What are we talking about? Frontiers in Psychology, 6, Article 51. Click here for full-text.

Beran, M. J. (2015). Animal memory: Chimpanzees anticipate what comes next in short movies. Current Biology, 25, R829-R830.

Beran, M. J., & Heimbauer, L. A. (2015). A longitudinal assessment of vocabulary retention in symbol-competent chimpanzees (Pan troglodytes).  PLoS ONE, 10, e0118408. Click here for full-text of the paper.

Beran, M. J., James, B. T.Futch, S. E., & Parrish, A. E. (2015). A comparative psychologist by any other name…is still a comparative psychologist. Commentary: A crisis in comparative psychology: Where have all the undergraduates gone? Frontiers in Psychology, 6, 1928.

Beran, M. J., Parrish, A. E.Futch, S. E., Evans, T. A., & Perdue, B. M. (2015).  Looking ahead? Computerized maze task performance by chimpanzees (Pan troglodytes), rhesus monkeys (Macaca mulatta), capuchin monkeys (Cebus apella), and human children (Homo sapiens). Journal of Comparative Psychology, 129, 160-173. NCBI Logo

Beran, M. J., Perdue, B. M., & Evans, T. A. (2015). Prospective memory in nonhuman primates. Japanese Journal of Animal Psychology, 65, 23-33.

Beran, M. J., Perdue, B. M., Futch, S. E., Smith, J. D., Evans, T. A., & Parrish, A. E. (2015). Go when you know: Chimpanzees’ confidence movements reflect their responses in a computerized memory task. Cognition, 142, 236-246.NCBI Logo

Parrish, A. E., Brosnan, S. F., & Beran, M. J. (2015). Do you see what I see? A comparative investigation of the Delboeuf illusion in humans (Homo sapiens), rhesus monkeys (Macaca mulatta) and capuchin monkeys (Cebus apella). Journal of Experimental Psychology: Animal Learning and Cognition, 41, 395-405.NCBI Logo

Parrish, A. E., Brosnan, S. F., & Beran, M. J. (2015). Capuchin monkeys alternate play and reward in a dual computerized task. Animal Behavior and Cognition, 2, 334-347. Click here for full paper.

Parrish, A. E., Evans, T. A., & Beran, M. J. (2015). Rhesus macaques (Macaca mulatta) exhibit the decoy effect in a perceptual discrimination task.  Attention, Perception, & Psychophysics, 77, 1715-1725.NCBI Logo

Parrish, A. E., Evans, T. A., & Beran, M. J. (2015). Defining value through quantity and quality – Chimpanzees (Pan troglodytes) undervalue food quantities when items are broken.  Behavioural Processes, 111, 118-126.NCBI Logo

Perdue, B. M., Bramlett, J. L., Evans, T. A., & Beran, M. J. (2015). Waiting for what comes later: Capuchin monkeys show self-control even for nonvisible delayed rewards. Animal Cognition, 18, 1105-1112.NCBI Logo

Perdue, B. M., Church, B. A., Smith, J. D., & Beran, M. J. (2015). Exploring potential mechanisms underlying the lack of uncertainty monitoring in capuchin monkeys. International Journal of Comparative Psychology, Article 28. Click here for full paper.

Sayers, K., Evans, T. A., Menzel, E., Smith, J. D., & Beran, M. J. (2015). The misbehaviour of a metacognitive monkey. Behaviour, 152, 727-756. NCBI Logo

Agrillo, C., Parrish, A. E., & Beran, M. J. (2014). Do primates see the Solitaire illusion differently? A comparative assessment of Humans (Homo sapiens), chimpanzees (Pan troglodytes), rhesus monkeys (Macaca mulatta) and capuchin monkeys (Cebus apella).  Journal of Comparative Psychology, 128, 402-413. NCBI Logo

Agrillo, C., Parrish, A. E., & Beran, M. J. (2014). Do rhesus monkeys (Macaca mulatta) perceive the Zöllner illusion?  Psychonomic Bulletin & Review, 21, 986-994. NCBI Logo

Beran, M. J., Evans, T. A., Paglieri, F., McIntyre, J. M., Addessi, E., & Hopkins, W. D. (2014). Chimpanzees (Pan troglodytes) can wait, when they choose to: A study with the hybrid delay task.  Animal Cognition, 17, 197-205. NCBI Logo

Beran, M. J., Parrish, A. E., Perdue, B. M., & Washburn, D. A. (2014). Comparative cognition: Past, present, and future.  International Journal of Comparative Psychology, 27, 3-30. Click here for full paper.

Beran, M. J., Perdue, B. M., & Smith, J. D. (2014). What are my chances? Closing the gap in uncertainty monitoring between rhesus monkeys (Macaca mulatta) and capuchin monkeys (Cebus apella). Journal of Experimental Psychology: Animal Learning and Cognition, 40, 303-316. NCBI Logo

Beran, M. J., & Smith, J. D. (2014). The uncertainty response in animal-metacognition researchers.  Journal of Comparative Psychology, 128, 155-159. NCBI Logo

Evans, T. A., & Beran, M. J. (2014). Monkeys wait to begin a computer task when waiting makes their responses more effective. Animal Behavior and Cognition, 1, 36-50. Click here for the full paper.

Evans, T. A., Perdue, B. M., Parrish, A. E., & Beran, M. J. (2014). The relationship between event-based prospective memory and ongoing task performance in chimpanzees (Pan troglodytes).  PLoS ONE, 9, e112015. Click here for full paper.

Evans, T. A., Perdue, B. M., Parrish, A. E., & Beran, M. J. (2014). Working and waiting for better rewards: Self-control in two monkey species (Cebus apella and Macaca mulatta).  Behavioural Processes, 103, 236-242. NCBI Logo

Garland, A., Beran, M. J., McIntyre, J. M., & Low, J. (2014). Relative quantity judgments between discrete spatial arrays by chimpanzees (Pan trogloydytes) and New Zealand robins (Petroica longipes).  Journal of Comparative Psychology, 128, 307-317. NCBI Logo

Parrish, A. E., & Beran, M. J. (2014). When less is more: Like humans, chimpanzees (Pan troglodytes) misperceive food amounts based on plate size. Animal Cognition, 17, 427-434. NCBI Logo

Parrish, A. E., & Beran, M. J. (2014). Chimpanzees sometimes see fuller as better: Judgments of food quantities based on container size and fullness. Behavioural Processes, 103, 184-191. NCBI Logo

Parrish, A. E., Brosnan, S. F., Wilson, B. J., & Beran, M. J. (2014).  Differential responding by rhesus monkeys (Macaca mulatta) and humans (Homo sapiens) to variable outcomes in the Assurance game. Animal Behavior and Cognition, 1, 215-229.Click here for full paper.

Parrish, A. E., Perdue, B. M., Stromberg, E. E., Bania, A. E., Evans, T. A., & Beran, M. J. (2014). Delay of gratification by orangutans (Pongo pygmaeus) in the accumulation task.  Journal of Comparative Psychology, 128, 209-214. NCBI Logo

Perdue, B. M., Beran, M. J., Williamson, R. A., Gonsiorowski, A., Evans, T. A. (2014). Prospective memory in children and chimpanzees.  Animal Cognition, 17, 287-295. NCBI Logo

Perdue, B. M., Evans, T. A., Washburn, D. A., Rumbaugh, D. M., & Beran, M. J. (2014). Do monkeys choose to choose?  Learning & Behavior, 42, 164-175. NCBI Logo

Smith, J. D., Couchman, J. J., & Beran, M. J. (2014). Animal metacognition: A tale of two comparative psychologies.  Journal of Comparative Psychology, 128, 115-131. NCBI Logo

Smith, J. D., Couchman, J. J., & Beran, M. J. (2014). Animal metacognition: A tale of two comparative psychologies – Reply to Commentaries.  Journal of Comparative Psychology, 128, 140-142. NCBI Logo

Vonk, J., Torgerson-White, L., McGuire, M., Thueme, M., Thomas, J., & Beran, M. J. (2014). Quantity estimation and comparison in Western Lowland Gorillas (Gorilla gorilla gorilla). Animal Cognition, 17, 755-765. NCBI Logo

Zakrzewski, A. C., Perdue, B. M., Beran, M. J., Church, B. A., & Smith, J. D. (2014). Cashing out: The decisional flexibility of uncertainty responses in rhesus macaques (Macaca mulatta) and humans (Homo sapiens). Journal of Experimental Psychology: Animal Learning and Cognition, 40, 490-501. NCBI Logo

Addessi, E., Paglieri, F., Beran, M. Evans, T. Macchitella, L., De Petrillo, F., & Focaroli, V. (2013).  Delay choice vs. delay maintenance: Different measures of delayed gratification in capuchin monkeys (Cebus apella).  Journal of Comparative Psychology, 127, 392-398. NCBI Logo

Beran, M. J., McIntyre, J. M., Garland, A., & Evans, T. A. (2013).  What counts for “counting”? Chimpanzees (Pan troglodytes) respond appropriately to relevant and irrelevant information in a quantity judgment task.  Animal Behaviour, 85, 987-993. NCBI Logo

Beran, M. J., & Parrish, A. E. (2013). Visual nesting of stimuli affects rhesus monkeys’ (Macaca mulatta) quantity judgments in a bisection task. Attention, Perception, & Psychophysics, 75, 1243-1251. NCBI Logo

Beran, M. J., Smith, J. D., & Perdue, B. M. (2013).  Language-trained chimpanzees name what they have seen, but look first at what they have not seen.  Psychological Science, 24, 660-666. NCBI Logo

Brosnan, S. F., Beran, M. J., Parrish, A. E., Price, S. A., & Wilson, B. J. (2013). Comparative approaches to studying strategy: Towards an evolutionary account of primate decision-making.  Evolutionary Psychology, 11, 606-627. NCBI Logo

Klein, E. D., Evans, T. A., Schultz, N. B., & Beran, M. J. (2013). Learning how to “make a deal”: Human and monkey performance when repeatedly faced with the Monty Hall Dilemma. Journal of Comparative Psychology, 127, 103-108. NCBI Logo

Paglieri, F., Focaroli, V., Bramlett, J., Tierno, V., McIntyre, J., Addessi, E., Evans, T. A., & Beran, M. J. (2013).  The hybrid delay task: Can capuchin monkeys (Cebus apella) sustain a delay after an initial choice to do so? Behavioural Processes, 94, 45-54. NCBI Logo

Parrish, A. E., Perdue, B. M., Evans, T. A., & Beran, M. J. (2013). Chimpanzees (Pan troglodytes) transfer token repeatedly with a partner to accumulate rewards in a self-control task. Animal Cognition, 16, 627-636. NCBI Logo

Smith, J. D., Coutinho, M. V. C., Church, B., & Beran, M. J. (2013). Executive-attentional uncertainty responses by rhesus monkeys (Macaca mulatta).  Journal of Experimental Psychology: General, 142, 458-475. NCBI Logo

Smith, J. D., Flemming, T. M., Boomer, J., Beran, M. J., & Church, B. A. (2013). Fading perceptual resemblance: A path for rhesus macaques (Macaca mulatta) to conceptual matching?  Cognition, 129, 598-614. NCBI Logo

Beran, M. J. (2012). Did you ever hear the one about the horse that could count?  Frontiers in Comparative Psychology, Article 257. Click here for full paper.

Beran, M. J. (2012). Quantity judgments of auditory and visual stimuli by chimpanzees (Pan troglodytes). Journal of Experimental Psychology: Animal Behavior Processes, 38, 23-29. NCBI Logo

Beran, M. J., Decker, S., Schwartz, A., & Smith, J. D. (2012). Uncertainty monitoring by young children in a computerized task.  Scientifica, 2012, Article 692890. Click here for full paper.

Beran, M. J., & Evans, T. A. (2012).  Language-trained chimpanzees (Pan troglodytes) delay gratification by choosing token exchange over immediate reward consumption.  American Journal of Primatology, 74, 864-870. NCBI Logo

Beran, M. J., Evans, T. A., Klein, E. D., & Einstein, G. O. (2012). Rhesus monkeys (Macaca mulatta) and capuchin monkeys (Cebus apella) remember future responses in a computerized task. Journal of Experimental Psychology: Animal Behavior Processes, 38, 233-243. NCBI Logo

Beran, M. J., Owens, K.Phillips, H. A., & Evans, T. A. (2012). Humans and monkeys show similar skill in estimating uncertain outcomes. Psychonomic Bulletin & Review, 19, 357-362. NCBI Logo

Beran, M. J., & Parrish, A. E. (2012). Sequential responding and planning in capuchin monkeys (Cebus apella).  Animal Cognition, 15, 1085-1094. NCBI Logo

Beran, M. J., Perdue, B. M., Bramlett, J. L., Menzel, C. R., & Evans, T. A. (2012). Prospective memory in a language-trained chimpanzee (Pan troglodytes). Learning and Motivation, 43, 192-199. NCBI Logo

Beran, M. J., Perdue, B. M., Parrish, A. E., & Evans, T. A. (2012). Do social conditions affect capuchin monkeys’ (Cebus apella) choices in a quantity judgment task? Frontiers in Comparative Psychology, 3, Article 492.  Click here for full-text PDF file.

Bramlett, J. L., Perdue, B. M., Evans, T. A., & Beran, M. J. (2012). Capuchin monkeys (Cebus apella) let lesser rewards pass them by to get better rewards. Animal Cognition, 15, 963-969. NCBI Logo

Brosnan, S. F., Wilson, B. J., & Beran, M. J. (2012). Old World monkeys are more similar to humans than New World monkeys when playing a coordination game.  Proceedings of the Royal Society of London, 279, 522-1530. NCBI Logo

Couchman, J. J., Beran, M. J., Coutinho, M. V. C.Boomer, J.Zakrzewski, A., Church, B. J., & Smith, J. D. (2012). Do actions speak louder than words? A comparative perspective on implicit vs. explicit metacognition and theory of mind. British Journal of Developmental Psychology, 30, 210-221. NCBI Logo

Evans, T. A., & Beran, M. J. (2012).  Monkeys exhibit prospective memory in a computerized task.  Cognition, 125, 131-140. NCBI Logo

Evans, T. A., Beran, M. J., Paglieri, F., Addessi, E. (2012). Delaying gratification for food and tokens in capuchin monkeys (Cebus apella) and chimpanzees (Pan troglodytes): When quantity is salient, symbolic stimuli do not improve performance. Animal Cognition, 15, 539-548. NCBI Logo

Evans, T. A., Perdue, B. M., Parrish, A. E., Menzel, E., Brosnan, S. F., & Beran, M. J. (2012). How is chimpanzee self-control influenced by social setting? Scientifica, Article ID 654094. Click here for full-text PDF file.

Heimbauer, L. A., Conway, C. M., Christiansen, M. H., Beran, M. J., & Owren, M. J. (2012).  A serial reaction time (SRT) task with symmetrical joystick responding for nonhuman primates.  Behavior Research Methods, 44, 733-741. NCBI Logo

Perdue, B. M., Talbot, C. F., Stone, A., & Beran, M. J. (2012).  Putting the elephant back in the herd: Elephant relative quantity judgments match those of other species.  Animal Cognition, 15, 955-961. NCBI Logo

Smith, J. D., Berg, M. E., Cook, R. G., Murphy, M. S., Crossley, M. J., Boomer, J., Spiering, B., Beran, M. J., Church, B. A., Ashby, F. G., & Grace, R. C. (2012).  Implicit and explicit categorization: A tale of four species.  Neuroscience and Biobehavioral Reviews, 36, 2355-2369. NCBI Logo

Smith, J. D., Couchman, J. J., & Beran, M. J. (2012). The highs and lows of theoretical interpretation in animal-metacognition research. Philosophical Transactions of the Royal Society B, 367, 1297-1309. NCBI Logo

Smith, J. D., Crossley, M. J., Boomer, J., Church, B. A., Beran, M. J., & Ashby, F. G. (2012). Implicit and explicit category learning by capuchin monkeys (Cebus apella). Journal of Comparative Psychology, 126, 294-304. NCBI Logo

Vonk, J., & Beran, M. J. (2012). Bears “count” too: Quantity estimation and comparison in black bears (Ursus americanus).  Animal Behaviour, 84, 231-238. NCBI Logo

Beran, M. J. (2011). Chimpanzees (Pan troglodytes) show the isolation effect during serial list recognition memory tests. Animal Cognition, 14, 637-645. NCBI Logo

Beran, M. J., Decker, S., Schwartz, A., & Schultz, N. (2011). Monkeys (Macaca mulatta and Cebus apella) and human adults and children (Homo sapiens) enumerate and compare subsets of moving stimuli based on numerosity. Frontiers in Comparative Psychology, 2, Article 61. Click here for full-text PDF file.

Beran, M. J., Evans, T. A., & Hoyle, D. (2011). Numerical judgments by chimpanzees (Pan troglodytes) in a token economy. Journal of Experimental Psychology: Animal Behavior Processes, 37, 165-174. NCBI Logo

Beran, M. J., Johnson-Pynn, J. S., & Ready, C. (2011). Comparing children’s (Homo sapiens) and chimpanzees’ (Pan troglodytes) quantity judgments of sequentially presented sets of items. Current Zoology, 57, 419-428.

Beran, M. J., & Smith, J. D. (2011). Information seeking by rhesus monkeys (Macaca mulatta) and capuchin monkeys (Cebus apella). Cognition, 120, 90-105. NCBI Logo

Brosnan, S. F., Parrish, A. E., Beran, M. J., Flemming, T., Heimbauer, L., Talbot, C., Lambeth, S. P., Shapiro, S. J., Wilson, B. J. (2011). Responses to the Assurance game in monkeys, apes, and humans using equivalent procedures. Proceedings of the National Academy of Sciences, 108, 3442-3447. NCBI Logo

Flemming, T. M., Thompson, R. K. R., Beran, M. J., & Washburn, D. A. (2011).  Analogical reasoning and the differential outcome effect: Transitory bridging of the conceptual gap for rhesus monkeys (Macaca mulatta).  Journal of Experimental Psychology: Animal Behavior Processes, 37, 353-360.NCBI Logo

Heimbauer, L. A., Beran, M. J., & Owren, M. J. (2011).  A chimpanzee recognizes synthetic speech with significantly reduced acoustic cues to phonetic content.  Current Biology, 21, 1210-1214. NCBI Logo

Klein, E. D., Evans, T. A., & Beran, M. J. (2011). An investigation of prospective and retrospective coding in capuchin monkeys and rhesus monkeys. Zeitschrift für Psychologie / Journal of Psychology, 219, 85-91.

Beran, M. J. (2010). Chimpanzees (Pan troglodytes) accurately compare poured liquid quantities. Animal Cognition, 13, 641-649. NCBI Logo

Beran, M. J. (2010). Use of exclusion by a chimpanzee (Pan troglodytes) during speech perception and auditory-visual matching-to-sample. Behavioural Processes, 83, 287-291. NCBI Logo

Couchman, J. J.Coutinho, M. V. C., Beran, M. J., Smith, J. D. (2010). Beyond stimulus cues and reinforcement signals: A new approach to animal metacognition. Journal of Comparative Psychology, 124, 356-368. NCBI Logo

Evans, T. A., Beran, M. J., & Addessi, E. (2010). Can nonhuman primates use tokens to represent and sum quantities? Journal of Comparative Psychology, 124, 369-380. NCBI Logo

Harris, E. H., Gulledge, J. P., Beran, M. J., & Washburn, D. A. (2010). What do Arabic numerals mean to macaques? Journal of Experimental Psychology: Animal Behavior Processes, 36, 66-76. NCBI Logo

Smith, J. D., Beran, M. J., Crossley, M., Boomer, J., & Ashby, F. G. (2010). Implicit and explicit category learning by macaques (Macaca mulatta) and humans (Homo sapiens). Journal of Experimental Psychology: Animal Behavior Processes, 36, 54-65. NCBI Logo

Smith, J. D., Redford, J. S., Beran, M. J., & Washburn, D. A. (2010).  Rhesus monkeys (Macaca mulatta) adaptively monitor uncertainty while multi-tasking. Animal Cognition, 13, 93-101.  NCBI Logo

Washburn, D. A., Gulledge, J. P., Beran, M. J., & Smith, J. D. (2010). With his memory magnetically erased, a monkey knows he is uncertain. Biology Letters, 6, 160-162. NCBI Logo

Beran, M. J. (2009). Chimpanzees as natural accountants.  Human Evolution, 24, 183-196. 

Beran, M. J., & Evans, T. A. (2009). Delay of gratification by chimpanzees (Pan troglodytes) in working and waiting situations. Behavioural Processes, 80, 117-121. NCBI Logo

Beran, M. J., Evans, T. A., & Harris, E. H. (2009). When in doubt, chimpanzees rely on estimates of past reward amounts.  Proceedings of the Royal Society B, 276, 309-314. NCBI Logo

Beran, M. J., Evans, T. A., & Ratliff, C. L. (2009). Perception of food amounts by chimpanzees (Pan troglodytes): The role of magnitude, contiguity, and wholeness. Journal of Experimental Psychology: Animal Behavior Processes, 35, 516-524. NCBI Logo

Beran, M. J., Ratliff, C. L., & Evans, T. A. (2009). Natural choice in chimpanzees (Pan troglodytes): Perceptual and temporal effects on selective value. Learning and Motivation, 40, 186-196.   NCBI Logo

Beran, M. J., Smith, J. D., Coutinho, M. V. C., Couchman, J. J., & Boomer, J. (2009). The psychological organization of “uncertainty” responses and “middle” responses: A dissociation in capuchin monkeys (Cebus apella). Journal of Experimental Psychology: Animal Behavior Processes, 35, 371-381. NCBI Logo

Brosnan, S. F., & Beran, M. J. (2009). Trade between conspecifics in chimpanzees (Pan troglodytes). Journal of Comparative Psychology, 123, 181-194. NCBI Logo

Evans, T. A. , Beran, M. J., Harris, E. H., & Rice, D. (2009).  Quantity judgments of sequentially presented food items by capuchin monkeys (Cebus apella). Animal Cognition, 12, 97-105. NCBI Logo

Hoffman, M. L., Beran, M. J., & Washburn, D. A. (2009).  Memory for ‘what,’ ‘where,’ and ‘when’ information in rhesus monkeys (Macaca mulatta).  Journal of Experimental Psychology: Animal Behavior Processes, 35, 143-152. NCBI Logo

Smith, J. D., Beran, M. J., Couchman, J. J., Coutinho, M. V. C., & Boomer, J. (2009). Animal metacognition: Problems and prospects. Comparative Cognition and Behavior Reviews, 4, 33-46.

Beran, M. J. (2008). Monkeys (Macaca mulatta and Cebus apella) track, enumerate, and compare multiple sets of moving items. Journal of Experimental Psychology: Animal Behavior Processes, 34, 63-74. NCBI Logo

Beran, M. J. (2008).  Capuchin monkeys (Cebus apella) succeed in a test of quantity conservation. Animal Cognition, 11, 109-116. NCBI Logo

Beran, M. J. (2008).  The evolutionary and developmental foundations of mathematics.  PLoS Biology, 6, e19. NCBI Logo

Beran, M. J., Evans, T. A., & Harris, E. H. (2008). Perception of food amount by chimpanzees based on the number, size, contour length, and visibility of items. Animal Behaviour, 75, 1793-1802. NCBI Logo

Beran, M. J., Evans, T. A., Leighty, K. A., Harris, E. H., & Rice, D. (2008).  Summation and quantity judgments of sequentially presented sets by capuchin monkeys (Cebus apella). American Journal of Primatology, 70, 191-194NCBI Logo

Beran, M. J., Harris, E. H., Evans, T. A., Klein, E. D., Chan, B., Flemming, T. M., & Washburn, D. A. (2008). Ordinal judgments of symbolic stimuli by capuchin monkeys (Cebus apella) and rhesus monkeys (Macaca mulatta): The effects of differential and nondifferential reward.  Journal of Comparative Psychology, 122, 52-61.  NCBI Logo

Beran, M. J., Johnson-Pynn, J. S., & Ready, C. (2008).  Quantity representation in children and rhesus monkeys: Linear versus logarithmic scales.  Journal of Experimental Child Psychology, 100, 225-233.  NCBI Logo

Beran, M. J., Klein, E. D., Evans, T. A., Chan, B., Flemming, T. M.Harris, E. H., Washburn, D. A., & Rumbaugh, D. M. (2008). Discrimination reversal learning in capuchin monkeys (Cebus apella).  Psychological Record, 58, 3-14.

Brosnan, S. F., Grady, M. F., Lambeth, S. P., Schapiro, S. J., & Beran, M. J. (2008). Chimpanzee autarky. PloS ONE, 3, e1518. NCBI Logo

Evans, T. A., Beran, M. J., Chan, B., Klein, E. D., & Menzel, C. R. (2008).  An efficient computerized testing method for the capuchin monkey (Cebus apella): Adaptation of the LRC-CTS to a socially housed nonhuman primate species.  Behavior Research Methods, 40, 590-596.  NCBI Logo

Flemming, T. M., Beran, M. J., Thompson, R. K. R., Kleider, H. M., & Washburn, D. A. (2008).  What meaning means for same and different: Analogical reasoning in humans (Homo sapiens), chimpanzees (Pan troglodytes), and rhesus monkeys (Macaca mulatta).  Journal of Comparative Psychology, 122, 176-185. NCBI Logo

Smith, J. D., Beran, M. J., Couchman, J. J., & Coutinho, M. V. C. (2008). The comparative study of metacognition: Sharper paradigms, safer inferences. Psychonomic Bulletin and Review, 15, 679-691. NCBI Logo

Beran, M. J. (2007). Rhesus monkeys (Macaca mulatta) enumerate large and small sequentially presented sets of items using analog numerical representations. Journal of Experimental Psychology: Animal Behavior Processes, 33, 42-54.NCBI Logo

Beran, M. J. (2007). Rhesus monkeys (Macaca mulatta) succeed on a computerized test designed to assess conservation of discrete quantity. Animal Cognition, 10, 37-45. NCBI Logo

Beran, M. J., Rumbaugh, D. M., & Washburn, D. A. (2007). Rhesus monkeys (Macaca mulatta) maintain learning set despite second-order stimulus-response spatial discontiguity. Psychological Record, 57, 9-22NCBI Logo

Beran, M. J., Washburn, D. A., & Rumbaugh, D. M. (2007).  A Stroop-like effect in color-naming of color-word lexigrams by a chimpanzee.  Journal of General Psychology, 134, 217-228.  NCBI Logo

Evans, T. A., & Beran, M. J. (2007). Chimpanzees use self-distraction to cope with impulsivity. Biology Letters, 3, 599-602.  NCBI Logo

Evans, T. A., & Beran, M. J. (2007). Delay of gratification and delay maintenance by rhesus macaques (Macaca mulatta). Journal of General Psychology, 134, 199-216. NCBI Logo

Flemming, T. M., Beran, M. J., & Washburn, D. A. (2007). Disconnect in concept learning by rhesus monkeys: Judgment of relations and relations-between-relations. Journal of Experimental Psychology: Animal Behavior Processes, 33, 55-63.NCBI Logo

Harris, E. H., Beran, M. J., & Washburn, D. A. (2007). Ordinal list integration for symbolic, arbitrary, and analog stimuli by rhesus macaques (Macaca mulatta). Journal of General Psychology, 134, 183-197. NCBI Logo

Harris, E. H., Washburn, D. A., Beran, M. J., & Sevcik, R. A. (2007). Rhesus monkeys (Macaca mulatta) select Arabic numerals or visible quantities corresponding to a number of sequentially completed maze trials. Learning and Behavior, 35, 53-59. NCBI Logo

Beran, M. J. (2006).  Quantity perception by adult humans (Homo sapiens), chimpanzees (Pan troglodytes), and rhesus macaques (Macaca mulatta) as a function of stimulus organization. International Journal of Comparative Psychology, 19, 386-397. Click here for full paper.

Beran, M. J., & Evans, T. A. (2006). Maintenance of delay of gratification by four chimpanzees (Pan troglodytes): The effects of delayed reward visibility, experimenter presence, and extended delay intervals. Behavioural Processes, 73, 315-324NCBI Logo

Beran, M. J., Smith, J. D., Redford, J. S., & Washburn, D. A. (2006). Rhesus macaques (Macaca mulatta) monitor uncertainty during numerosity judgments. Journal of Experimental Psychology: Animal Behavior Processes, 32, 111-119. NCBI Logo

Beran, M. J., Taglialatela, L. B.Flemming, T. M.James, F. M., & Washburn, D. A. (2006). Nonverbal estimation during numerosity judgments by adult humans. Quarterly Journal of Experimental Psychology, 59, 2065-2082. NCBI Logo

Hoffman, M. L., & Beran, M. J. (2006). Chimpanzees (Pan troglodytes) remember the location of a hidden food item after altering their orientation to a spatial array. Journal of Comparative Psychology, 120, 389-393. NCBI Logo

Smith, J. D., Beran, M. J., Redford, J. S., & Washburn, D. A. (2006). Dissociating uncertainty responses and reinforcement signals in the comparative study of uncertainty monitoring. Journal of Experimental Psychology: General, 135, 282-297. NCBI Logo

Beran, M. J., Beran, M. M., Harris, E. H., & Washburn, D. A. (2005).  Ordinal judgments and summation of nonvisible sets of food items by two chimpanzees (Pan troglodytes) and a rhesus macaque (Macaca mulatta).  Journal of Experimental Psychology: Animal Behavior Processes, 31, 351-362. NCBI Logo

Beran, M. J., Beran, M. M., & Menzel, C. R. (2005). Chimpanzees (Pan troglodytes) use markers to monitor the movement of a hidden food item. Primates, 46, 255-259. NCBI Logo

Beran, M. J., Beran, M. M., & Menzel, C. R. (2005). Spatial memory and monitoring of hidden items through spatial displacements by chimpanzees (Pan troglodytes). Journal of Comparative Psychology, 119, 14-22. NCBI Logo

Beran, M. J. (2004). Long-term retention of the differential values of Arabic numerals by chimpanzees (Pan troglodytes). Animal Cognition, 7, 86-92. NCBI Logo

Beran, M. J. (2004). Chimpanzees (Pan troglodytes) respond to nonvisible sets after one-by-one addition and removal of items. Journal of Comparative Psychology, 118, 25-36. NCBI Logo

Beran, M. J., & Beran, M. M. (2004). Chimpanzees remember the results of one-by-one addition of food items to sets over extended time periods. Psychological Science, 15, 94-99. NCBI Logo

Beran, M. J., Pate, J. L., Washburn, D. A., & Rumbaugh, D. M. (2004). Sequential responding and planning in chimpanzees (Pan troglodytes) and rhesus macaques (Macaca mulatta). Journal of Experimental Psychology: Animal Behavior Processes, 30, 203-212. NCBI Logo

Beran, M. J., & Washburn, D. A. (2002). Chimpanzee responding during matching to sample: Control by exclusion. Journal of the Experimental Analysis of Behavior, 78, 497-508. NCBI Logo

Beran, M. J. (2002). Maintenance of self-imposed delay of gratification by four chimpanzees (Pan troglodytes) and an orangutan (Pongo pygmaeus). Journal of General Psychology, 129, 49-66. NCBI Logo

Beran, M. J. (2001). Summation and numerousness judgments of sequentially presented sets of items by chimpanzees (Pan troglodytes). Journal of Comparative Psychology, 155, 181-191. NCBI Logo

Beran, M. J. (2001). Do chimpanzees have expectations about reward presentation following correct performance on computerized cognitive testing? Psychological Record, 51, 173-183.

Beran, M. J., & Rumbaugh, D. M (2001). “Constructive” enumeration by chimpanzees (Pan troglodytes) on a computerized task. Animal Cognition, 4, 81-89.

Beran, M. J., & Minahan, M. F. (2000). Monitoring spatial transpositions by bonobos (Pan paniscus) and chimpanzees (Pan troglodytes). International Journal of Comparative Psychology, 13, 1-15.

Beran, M. J., Pate, J. L., Richardson, W. K., & Rumbaugh, D. M. (2000). A chimpanzee’s (Pan troglodytes) long-term retention of lexigrams. Animal Learning and Behavior, 28, 201-207.

Beran, M. J., Savage-Rumbaugh, E. S., Pate, J. L., & Rumbaugh, D. M. (1999). Delay of gratification in chimpanzees (Pan troglodytes). Developmental Psychobiology, 34, 119-127.

Beran, M. J., Rumbaugh, D. M., & Savage-Rumbaugh, E. S. (1998). Chimpanzee (Pan troglodytes) counting in a computerized testing paradigm. Psychological Record, 48, 3-20.

Beran, M. J., Savage-Rumbaugh, E. S., Brakke, K. E., Kelley, J. W., & Rumbaugh, D. M. (1998). Symbol comprehension and learning: A “vocabulary” test of three chimpanzees (Pan troglodytes). Evolution of Communication, 2, 171-188.