Language comprehension in the great apes has been investigated through a variety of paradigms. This experiment employed a match-to-sample computer task to investigate the current language comprehension of three chimpanzees (Pan troglodytes) raised in different language environments but with a similar symbol system (lexigrams). Each of these animals still uses the lexigram keyboard system on a daily basis but none of the animals are the focus of ongoing ape language research programs. Six testing conditions were employed utilizing photographs, lexigrams and spoken English. The results indicated that all apes retained knowledge of at least some of the symbols that they had previously learned, and they each learned differing numbers of new lexigrams that were never taught to them. This indicates that rearing history is important not only in initial symbol acquisition in apes, but also in extended recall of the symbols, particularly when those symbols are used infrequently later in life. Differences in the current ages of these apes requires that such a conclusion be made tentatively, and suggests the need to continue the examination of symbol vocabulary size at various times throughout the life of each ape.
2001. Summation and numerousness judgments of sequentially presented sets of items by chimpanzees (Pan troglodytes).. Journal of Comparative Psychology 115:2 ► pp. 181 ff.
Beran, Michael J.
2002. Maintenance of Self-Imposed Delay of Gratification by Four Chimpanzees (Pan troglodytes) and an Orangutan (Pongo pygmaeus). The Journal of General Psychology 129:1 ► pp. 49 ff.
Beran, Michael J.
2010. Use of exclusion by a chimpanzee (Pan troglodytes) during speech perception and auditory–visual matching-to-sample. Behavioural Processes 83:3 ► pp. 287 ff.
Beran, Michael J.
2011. Chimpanzees (Pan troglodytes) show the isolation effect during serial list recognition memory tests. Animal Cognition 14:5 ► pp. 637 ff.
Beran, Michael J., Lisa A. Heimbauer & Kim A. Bard
2015. A Longitudinal Assessment of Vocabulary Retention in Symbol-Competent Chimpanzees (Pan troglodytes). PLOS ONE 10:2 ► pp. e0118408 ff.
Beran, Michael J. & David A. Washburn
2002. CHIMPANZEE RESPONDING DURING MATCHING TO SAMPLE: CONTROL BY EXCLUSION. Journal of the Experimental Analysis of Behavior 78:3 ► pp. 497 ff.
Evans, Theodore A., Bonnie Perdue, Michael J. Beran & Sam Gilbert
2014. The Relationship between Event-Based Prospective Memory and Ongoing Task Performance in Chimpanzees (Pan troglodytes). PLoS ONE 9:11 ► pp. e112015 ff.
Heimbauer, Lisa A., Michael J. Beran & Michael J. Owren
2011. A Chimpanzee Recognizes Synthetic Speech with Significantly Reduced Acoustic Cues to Phonetic Content. Current Biology 21:14 ► pp. 1210 ff.
Hillix, William A. & Duane M. Rumbaugh
2004. Lana Learns Lexigrams. In Animal Bodies, Human Minds: Ape, Dolphin, and Parrot Language Skills, ► pp. 125 ff.
Krause, Mark A. & Michael J. Beran
2020. Words matter: Reflections on language projects with chimpanzees and their implications. American Journal of Primatology 82:10
Love, Melany & David A. Washburn
2018. Computerized Testing Paradigm in Primates. In Encyclopedia of Animal Cognition and Behavior, ► pp. 1 ff.
Love, Melany & David A. Washburn
2022. Computerized Testing Paradigm in Primates. In Encyclopedia of Animal Cognition and Behavior, ► pp. 1595 ff.
Schwartz, Bennett L., Megan L. Hoffman & Siân Evans
2005. Episodic-like memory in a gorilla: A review and new findings. Learning and Motivation 36:2 ► pp. 226 ff.
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