Peer-reviewed research
Five decades of evidence for the thinking parrot.
Dr. Irene Pepperberg has studied the intelligence and reasoning of the African Grey parrot for nearly 50 years, publishing extensively in the most respected journals in her field. Selected work is below, with PDFs and DOIs where available.
Cognitive and communicative behavior of Grey parrots
Encyclopedia of Language and Linguistics. Elsevier.
Grey parrots: Studies in avian cognition
Encyclopedia of Animal Behavior (pp. 220–231). Elsevier.
Comments on consciousness in Grey parrots (Psittacus erithacus)
Comparative Cognition & Behavior Reviews, 21, 045–049.
A test of inference by exclusion in Grey parrots (Psittacus erithacus): Replication of a parrot–child comparative study using additional avian subjects
Journal of Comparative Psychology, 140(2), 155–159.
Examination of hierarchical form perception in African Grey parrots (Psittacus erithacus)
Learning & Behavior.
Contrafreeloading in umbrella cockatoos (Cacatua alba): Further evaluation of the play hypothesis
Journal of Comparative Psychology, 139(2), 84–97.
Putting the best foot forward: Limb lateralization in the Goffin's cockatoo (Cacatua goffiniana)
Journal of Comparative Psychology, 139(2), 98–110.
Comments on "Comparing the productive vocabularies of Grey parrots (Psittacus erithacus) and young children"
Animal Cognition, 27, Article 79.
A study of executive function in Grey parrots: Experience can affect delay of gratification
Journal of Comparative Psychology, 138(1), 8–19.
Exploring the utility of robots as distractors during a delay-of-gratification task in preschool children
Frontiers in Robotics and AI, 10.
Animal-computer interfaces: Novel approaches for studying animal behavior, cognition and communication
Interaction Studies, 24(2), 193–200.
How studies of communication among nonhumans and between humans and nonhumans can inform SETI (Ch. 6)
In D. Vakoch & J. Castrovinci (Eds.), Xenolinguistics: Toward a science of extraterrestrial language. Routledge, Taylor & Francis.
Contrafreeloading in kea (Nestor notabilis) in comparison to Grey parrots (Psittacus erithacus)
Scientific Reports, 12, 17415.
Comments on "Intra- and interspecific variation in self-control capacities of parrots in a delay of gratification task"
Animal Cognition, 25(6), 1679–1682.
Implications of wild cockatoos manufacturing and using tools
Learning & Behavior, 50, 205–206.
The value of collaboration between animal cognition and cognitive science (opinion)
In&Vertebrates.
Delayed gratification: A Grey parrot (Psittacus erithacus) will wait for more tokens
Journal of Comparative Psychology, 136, 79–89.
Initial evidence for contrafreeloading in Grey parrots via the opportunity for playful foraging
Journal of Comparative Psychology, 135(4), 516–533.
Evidence for abstract representations of the relations same-different in a Grey parrot
Current Opinion in Behavioral Sciences, 37, 146–152.
Nonhuman communication: Some issues and questions
Frontiers in Psychology, 12, 647841.
A review of the Model/Rival (M/R) technique for training interspecies communication
Animals, 11, 2479.
Does captivity alter problem-solving behavior in Goffin's cockatoos?
Learning & Behavior, 49, 1–2.
Symbolic communication in the Grey parrot
In A. Kaufman & J. Call (Eds.), Cambridge Handbook of Animal Cognition (pp. 56–73). Cambridge University Press.
Age and species comparisons of visual mental manipulation ability as evidence for its development and evolution
Scientific Reports, 10, 7689.
Piagetian liquid overconservation in Grey parrots (Psittacus erithacus)
Journal of Comparative Psychology, 143, 197–210.
The comparative psychology of intelligence: Some thirty years later
Frontiers in Psychology, 11, 973.
Vocal communication in nonhuman animals: View from the wings
Animal Behavior and Cognition, 7(2), 95–100.
Human-avian comparisons in cognitive performance
In L. Workman, W. Reader, & J. Barkow (Eds.), Cambridge Handbook of Evolutionary Perspectives on Human Behavior (pp. 3–13). Cambridge University Press.
Logical reasoning by a Grey parrot (Psittacus erithacus)? A case study of the disjunctive syllogism
Behaviour, 156, 409–445.
Animal sentience is not enough to motivate conservation (commentary)
Animal Sentience, 21(3).
Grey parrots: Studies in avian cognition
In J. Choe (Ed.), Encyclopedia of Animal Behavior (2nd ed., pp. 83–89). Elsevier.
Initial evidence for probabilistic learning by a Grey parrot (Psittacus erithacus)
Journal of Comparative Psychology, 132, 166–177.
Grey parrots: Cognitive and communicative abilities
In N. Bueno & F. Amici (Eds.), A Practical Guide to Animal Cognition. Cambridge University Press.
Tool use in Goffin's cockatoos: Shape/frame matching
Learning & Behavior, 47, 1–2.
Zero concept
In J. Vonk & T. Shackelford (Eds.), Encyclopedia of Animal Behavior and Cognition. Springer.
Cardinality
In J. Vonk & T. Shackelford (Eds.), Encyclopedia of Animal Behavior and Cognition. Springer.
Piagetian liquid conservation in Grey parrots (Psittacus erithacus)
Journal of Comparative Psychology, 131, 370–383.
"Birdbrains" should not be ignored in studying the evolution of g (commentary)
Behavioral and Brain Sciences, 40, e216.
Review of studies on visual perception in Grey parrots: The Müller-Lyer illusion, modal and amodal completion
Animal Behavior & Cognition, 4(3), 378–395.
Animal language studies: What happened?
Psychonomic Bulletin & Review, 24, 181–185.
Alex the Parrot
In J. Vonk & T. K. Shackelford (Eds.), Encyclopedia of Animal Cognition and Behavior. Springer.
Avian numerical cognition
In S. Healy & C. ten Cate (Eds.), Avian Cognition. Cambridge University Press.
What is comparative psychology?
In APA Handbook of Comparative Psychology. American Psychological Association.
Symbolic communication in nonhumans
In APA Handbook of Comparative Psychology. American Psychological Association.
Interspecific communication
In APA Handbook of Comparative Psychology. American Psychological Association.
Robust representation of shape by a Grey parrot (Psittacus erithacus)
Cognition, 153, 146–160.
Developmental plasticity and language: A comparative perspective
Topics in Cognitive Science, 8, 435–445.
Delayed gratification: A Grey parrot (Psittacus erithacus) will wait for a better reward
Journal of Comparative Psychology, 129(4), 339–346.
Reply to Jaakkola (2014): "Do animals understand invisible displacements? A critical review"
Journal of Comparative Psychology, 129(2), 198–201.
Innovation and creativity in a Grey parrot
In A. Kaufman & J. Kaufman (Eds.), Animal Creativity and Innovation (pp. 3–25). Elsevier.
Numerical concepts: Grey parrot capacities
In D. Geary, D. Berch, & K. M. Koepke (Eds.), Evolutionary Origins and Early Development of Basic Number Processing (pp. 67–90). Elsevier.
Do Grey parrots (Psittacus erithacus) succeed on a "complex" foraging task failed by primates but solved by fish?
Journal of Comparative Psychology, 128, 298–306.
Language learning in avians
In P. Brooks, V. Kempe, & J. G. Golson (Eds.), Encyclopedia of Language Development. Sage.
Reasoning by inference: Further studies on exclusion in Grey parrots (Psittacus erithacus)
Journal of Comparative Psychology, 127, 272–281.
A study of reciprocity in Grey parrots (Psittacus erithacus)
Animal Cognition, 16, 197–210.
Abstract concepts: Data from a Grey parrot
Behavioural Processes, 93, 82–90.
Evolution of vocal communication: An avian model
In J. Bolhuis & M. Everaert (Eds.), Birdsong, Speech and Language (Ch. 26). MIT Press.
Phonological awareness in Grey parrots
In J. Bolhuis & M. Everaert (Eds.), Birdsong, Speech, and Language (Ch. 13). MIT Press.
Interspecies communication with Grey parrots: A tool for examining cognitive processing
In G. Witzany (Ed.), Biocommunication of Animals. Springer.
Grey parrot number acquisition: The inference of cardinal value from ordinal position on the numeral list
Cognition, 125(2), 219–232.
Further evidence for addition and numerical competence by a Grey parrot (Psittacus erithacus)
Animal Cognition, 15, 711–717.
Emotional birds—or advanced cognitive processing?
In S. Watanabe & S. Kuczaj (Eds.), Emotions of Animals and Humans: Comparative Perspectives. Springer.
Referential vocal learning by Grey parrots
In N. Seel (Ed.), Encyclopedia of the Sciences of Learning. Springer.
Symbolic communication in the Grey parrot
In J. Vonk & T. Shackelford (Eds.), Oxford Handbook of Comparative Evolutionary Psychology. Oxford University Press.
The evolution of learning to communicate: An avian model for the missing link
In T. Schilhab, F. Stjernfelt, & T. Deacon (Eds.), The Symbolic Species Evolved. Springer.
Avian cognition and social interaction: Fifty years of advances
Interaction Studies, 12, 195–207.
Evolution of communication and language: Insights from parrots and songbirds
In M. Tallerman & K. Gibson (Eds.), Handbook on Language Evolution. Oxford University Press.
Language evolution from an avian perspective
In M. Papini & G. Gutierrez (Eds.), Darwin and the Behavioral Sciences.
Vocal learning in Grey parrots: A brief review of perception, production, and cross-species comparisons
Brain & Language, 115(1), 81–91.
The question of avian awareness
In A. Farrachi (Ed.), Justification of the Strongest. Radicaux Press.
Alex: A study in avian cognition
In M. Breed & J. Moore (Eds.), Encyclopedia of Animal Behavior. Academic Press.
Entrainment to music requires vocal mimicry: Evidence from nonhuman animals
Current Biology, 19, 831–836.
Grey parrot (Psittacus erithacus) vocal learning: Creation of new labels from existing vocalizations
In LACUS Forum 34: Speech and Beyond (pp. 21–30).
The Müller-Lyer illusion is processed by a Grey parrot (Psittacus erithacus)
Perception, 37, 765–781.
Difficulties with 'humaniqueness' (commentary)
Behavioral and Brain Sciences, 31, 143–144.
Grey parrots do not always 'parrot': Phonological awareness and the creation of new labels from existing vocalizations
Language Sciences, 29(1), 1–13.
Individual differences in Grey parrots (Psittacus erithacus): Effects of training
Journal of Ornithology, 148(Suppl. 2), 161–168.
Training behavior by imitation: From parrots to people…to robots?
In C. Nehaniv & K. Dautenhahn (Eds.), Imitation and Social Learning in Robots, Humans and Animals. Cambridge University Press.
Ordinality and inferential abilities of a Grey parrot (Psittacus erithacus)
Journal of Comparative Psychology, 120(3), 205–216.
Grey parrot (Psittacus erithacus) numerical abilities: Addition and further experiments on a zero-like concept
Journal of Comparative Psychology, 120(1), 1–11.
Grey parrot numerical competence: A review
Animal Cognition, 8, 377–391.
Cognitive and communicative abilities of Grey parrots (Psittacus erithacus)
In A. Luescher (Ed.), Manual of Parrot Behavior. Iowa State University Press.
Rational birds?
In S. Hurley & M. Nudds (Eds.), Rational Animals? Oxford University Press.
Numerical comprehension by a Grey parrot (Psittacus erithacus), including a zero-like concept
Journal of Comparative Psychology, 119(2), 197–209.
Insights into vocal imitation in Grey parrots (Psittacus erithacus)
In S. Hurley & N. Chater (Eds.), Perspectives on Imitation: From Neuroscience to Social Science. MIT Press.
Evolution of language from an avian perspective
In M. Tallerman (Ed.), Language Origins: Perspectives on Evolution. Oxford University Press.
"Insightful" string-pulling in Grey parrots (Psittacus erithacus) is affected by vocal competence
Animal Cognition, 7, 263–266.
Lack of referential vocal learning from LCD video by Grey parrots (Psittacus erithacus)
Interaction Studies, 5(1), 75–97.
Human speech: Its learning and use by Grey parrots
In P. Marler & H. Slabbekoorn (Eds.), Nature's Music. Elsevier.
The evolution of communication from an avian perspective
In D. K. Oller & U. Griebel (Eds.), The Evolution of Communication Systems: A Comparative Approach. MIT Press.
The value of the Piagetian framework for comparative cognitive studies
Animal Cognition, 5, 177–182.
In search of King Solomon's ring: Cognition and communication in Grey parrots
Brain, Behavior and Evolution, 59, 54–67.
Cognitive and communicative abilities of Grey parrots
Current Directions in Psychological Science, 11, 83–87.
Cognitive and communicative abilities of Grey parrots (Psittacus erithacus)
In M. Bekoff, C. Allen, & G. Burghardt (Eds.), The Cognitive Animal. MIT Press.
Simultaneous development of vocal and physical object combinations by a Grey parrot (Psittacus erithacus): Bottle caps, lids, and labels
Journal of Comparative Psychology, 115(4), 376–384.
Lessons from cognitive ethology: Animal models for ethological computing
Proceedings of the First Conference on Epigenetic Robotics (Lund University Cognitive Science Series No. 85).
Avian cognitive abilities
Bird Behavior, 14, 51–70.
Evolution of avian intelligence
In R. Sternberg & J. Kaufman (Eds.), The Evolution of Intelligence. Erlbaum.
Perceptual consciousness in Grey parrots
American Zoologist, 40, 893–901.
Vocal learning in the Grey parrot (Psittacus erithacus): Effect of species identity and number of trainers
Journal of Comparative Psychology, 114, 371–380.
Evidence for a form of mutual exclusivity during label acquisition by Grey parrots (Psittacus erithacus)?
Journal of Comparative Psychology, 114(3), 219–231.
Limited contextual vocal learning in the Grey parrot (Psittacus erithacus): The effect of co-viewers on videotaped instruction
Journal of Comparative Psychology, 113, 158–172.
The Alex Studies: Cognitive and Communicative Abilities of Grey Parrots
Harvard University Press.
Measurement of the trachea of the Grey parrot (Psittacus erithacus) via Magnetic Resonance Imaging, dissection and Electron Beam Computed Tomography
Journal of Morphology, 238, 81–91.
Allospecific vocal learning by Grey parrots (Psittacus erithacus): A failure of videotaped instruction under certain conditions
Behavioural Processes, 42, 139–158.
A comparative study of human and Grey parrot phonation: Acoustic and articulatory correlates of stop consonants
Journal of the Acoustical Society of America, 103, 2197–2213.
Animal Cognition in Nature: The convergence of psychology and biology in laboratory and field
Academic Press.
Development of Piagetian object permanence in a Grey parrot (Psittacus erithacus)
Journal of Comparative Psychology, 111, 63–75.
Effect of avian-human joint attention on vocal learning by Grey parrots (Psittacus erithacus)
Journal of Comparative Psychology, 110, 286–297.
Mechanisms of American English vowel production in a Grey parrot (Psittacus erithacus)
The Auk, 113, 41–58.
Mirror use by African Grey parrots (Psittacus erithacus)
Journal of Comparative Psychology, 109, 182–195.
A comparative study of human and parrot phonation: Acoustic and articulatory correlates of vowels
Journal of the Acoustical Society of America, 96, 634–648.
Numerical competence in an African Grey parrot
Journal of Comparative Psychology, 108(1), 36–44.
Vocal learning in African Grey parrots: Effects of social interaction, reference and context
The Auk, 111, 300–313.
Interspecific communication between humans and a parrot: A two-way communication code facilitates study of the cognitive capacities of an avian subject
Zeitschrift für Semiotik, 15, 41–67.
A review of the effects of social interaction on vocal learning in African Grey parrots (Psittacus erithacus)
Netherlands Journal of Zoology, 43, 104–124.
Proficient performance of a conjunctive, recursive task by an African Grey parrot (Psittacus erithacus)
Journal of Comparative Psychology, 106(3), 295–305.
A synthesis of ethology and psychology: Effects of social interaction on learning in avian species
In H. Davis & D. Balfour (Eds.), The Inevitable Bond. Cambridge University Press.
Relational learning by an African Grey parrot (Psittacus erithacus): Discriminations based on relative size
Journal of Comparative Psychology, 105(3), 286–294.
Solitary sound play during acquisition of English vocalizations by an African Grey parrot (Psittacus erithacus): Possible parallels with children's monologue speech
Applied Psycholinguistics, 12, 151–177.
Language acquisition and use in a bilingual environment: A framework for studying birdsong in zones of sympatry
Ethology, 89, 1–28.
A communicative approach to animal cognition: Some conceptual abilities of an African Grey parrot
In C. Ristau (Ed.), Cognitive Ethology: The Minds of Other Animals. Erlbaum.
Cognition in an African Grey parrot (Psittacus erithacus): Further evidence for comprehension of categories and labels
Journal of Comparative Psychology, 104(1), 41–52.
Referential mapping: Attaching functional significance to the innovative utterances of an African Grey parrot (Psittacus erithacus)
Applied Psycholinguistics, 11(1), 23–44.
Object permanence in four species of psittacine birds
Animal Learning & Behavior, 18, 97–108.
An investigation into the cognitive capacities of an African Grey parrot (Psittacus erithacus)
In P. J. B. Slater, J. S. Rosenblatt, & C. Beer (Eds.), Advances in the Study of Behavior. Academic Press.
An interactive modeling technique for acquisition of communication skills: Separation of 'labeling' and 'requesting' in a psittacine subject
Applied Psycholinguistics, 9(1), 59–76.
Acquisition of the concept of absence by an African Grey parrot: Learning with respect to questions of same/different
Journal of the Experimental Analysis of Behavior, 50(3), 553–564.
Second language acquisition: A framework for studying the importance of input and interaction in exceptional song acquisition
Ethology, 77, 150–168.
An avian model for studies on second language acquisition
Studies in Second Language Acquisition, 10, 1–11.
Evidence for conceptual quantitative abilities in the African Grey parrot: Labeling of cardinal sets
Ethology, 75, 37–61.
Acquisition of the same/different concept by an African Grey parrot (Psittacus erithacus): Learning with respect to categories of color, shape, and material
Animal Learning & Behavior, 15(4), 423–432.
Object permanence in the African Grey parrot (Psittacus erithacus)
Animal Learning & Behavior, 14, 322–330.
Social modeling theory: A possible framework for avian vocal learning
The Auk, 102, 854–864.
Cognition in the African Grey parrot: Preliminary evidence for auditory/vocal comprehension of the class concept
Animal Learning & Behavior, 11(2), 179–185.
Functional vocalizations by an African Grey parrot (Psittacus erithacus)
Zeitschrift für Tierpsychologie, 55(2), 139–160.
Extended topological rules for boron hydrides
Inorganic Chemistry, 16, 363ff (1977).
The question of fluxional behavior in B₃H₈⁻ and B₅H₁₁
Inorganic Chemistry, 17, 587ff (1978).
A molecular orbital study of the role of BH₅ in the hydrolysis of BH₄⁻
Journal of the American Chemical Society, 98, 3442ff (1976).
Computational evidence for a stable intermediate in the rearrangement of 1,2-C₂B₄H₆ to 1,6-C₂B₄H₆
Journal of the American Chemical Society, 97, 1248ff (1975).
Localized molecular orbitals and chemical reactions II
Journal of the American Chemical Society, 96, 1325ff (1973).
Features, interviews, and news about the Pepperberg birds and the science of avian cognition.
- Exploring the Significant Intelligence of the African Grey Parrot, with Dr. Irene PepperbergFinding Genius Podcast
- Special Issue in Honor of the Contributions of Irene PepperbergPsychonomic Society
- L&B Special Issue: Interview with Irene PepperbergPsychonomic Society
- A Special Issue in Honor of Irene Pepperberg: The Chemist of Comparative CognitionSpringer Nature
- This African Grey Parrot Is the First Animal to Ever Ask an Existential QuestionMy Modern Met
- "Birds of a Feather," featuring Alex & MeThe Moth
- Top Gazette Stories of 2020Harvard Gazette
- 10 Times Science Made a Sucky Year Suck LessLive Science
- Alex Understands a Zero-Like ConceptLive Science
- Parrot Proves It's No BirdbrainWIRED
- That Damn BirdEdge.org