Mental representation of symbols as revealed by vocabulary errors in two bonobos (Pan paniscus)

Abstract

Error analysis has been used in humans to detect implicit representations and categories in language use. The present study utilizes the same technique to report on mental representations and categories in symbol use from two bonobos (Pan paniscus). These bonobos have been shown in published reports to comprehend English at the level of a two-and-a-half year old child and to use a keyboard with over 200 visuographic symbols (lexigrams). In this study, vocabulary test errors from over 10 years of data revealed auditory, visual, and spatio-temporal generalizations (errors were more likely items that looked like sounded like, or were frequently associated with the sample item in space or in time), as well as hierarchical and conceptual categorizations. These error data, like those of humans, are a result of spontaneous responding rather than specific training and do not solely depend upon the sample mode (e.g. auditory similarity errors are not universally more frequent with an English sample, nor were visual similarity errors universally more frequent with a photograph sample). However, unlike humans, these bonobos do not make errors based on syntactical confusions (e.g. confusing semantically unrelated nouns), suggesting that they may not separate syntactical and semantic information. These data suggest that apes spontaneously create a complex, hierarchical, web of representations when exposed to a symbol system.

The role of dialogue in the ontogeny and phylogeny of early symbol combinations: A cross-species comparison of bonobo, chimpanzee, and human learners

“…However, research examining the nature of the errors apes make during vocabulary tests suggests that their errors are not random (Lyn, 2007). Many errors are driven by proximity wherein the ape selects a symbol that is physically close to the symbol she meant to select.…”

Am I looking at a cat or a dog? Gaze in the semantic variant of primary progressive aphasia is subject to excessive taxonomic capture

“…Although seemingly simple, from an information processing standpoint this ability is remarkable: humans are able to recognize a seemingly limitless number of common objects, and to map them onto their respective nouns with great precision. This capacity dwarfs that of non-human species (dogs, parrots, apes, etc), the most gifted of which have an “object vocabulary” in the hundreds to low thousands (Kaminski, Call, & Fischer, 2004; Lyn, 2007; Pepperberg, 2002; Pilley & Reid, 2011). In contrast, even conservative estimates place average human vocabulary in the tens of thousands of words (Zechmeister, Chronis, Cull, D’Anna, & Healy, 1995), with a significant proportion of these being object-referential nouns, particularly in early stages of language acquisition (Gentner & Boroditsky, 2001).…”

Language-Trained Animals: A Window to the “Black Box”

“…In the case of parrots, it seems that they used something like the over-extension strategy, by using a few food labels to ask for all food items and a few object labels for all object items. This type of error in the mechanism of information treatment was also observed in language-trained apes [38,63]. Pepperberg, without having formerly tested categorization with her parrots, reports that when Alex erred on, for example, a color label for objects, he most often provided another color label [46,77].…”

“…[37] Lana learned to chain lexigrams into strings that were similar to human sentences. Heidi Lyn showed that the vocabulary errors produced during tenyear data collecting period for Kanzi and Pabanisha revealed that apes are able spontaneously to create a complex, hierarchical, web of representations when exposed to a symbol system (lexigrams) [63]. The Californian sea lion show some understanding of semantic [42].…”