45 research outputs found
Investigating Speech Perception in Evolutionary Perspective: Comparisons of Chimpanzee (Pan troglodytes) and Human Capabilities
There has been much discussion regarding whether the capability to perceive speech is uniquely human. The âSpeech is Specialâ (SiS) view proposes that humans possess a specialized cognitive module for speech perception (Mann & Liberman, 1983). In contrast, the âAuditory Hypothesisâ (Kuhl, 1988) suggests spoken-language evolution took advantage of existing auditory-system capabilities. In support of the Auditory Hypothesis, there is evidence that Panzee, a language-trained chimpanzee (Pan troglodytes), perceives speech in synthetic âsine-waveâ and ânoise-vocodedâ forms (Heimbauer, Beran, & Owren, 2011). Human comprehension of these altered forms of speech has been cited as evidence for specialized cognitive capabilities (Davis, Johnsrude, Hervais-Adelman, Taylor, & McGettigan, 2005).
In light of Panzeeâs demonstrated abilities, three experiments extended these investigations of the cognitive processes underlying her speech perception. The first experiment investigated the acoustic cues that Panzee and humans use when identifying sine-wave and noise-vocoded speech. The second experiment examined Panzeeâs ability to perceive âtime-reversedâ speech, in which individual segments of the waveform are reversed in time. Humans are able to perceive such speech if these segments do not much exceed average phoneme length. Finally, the third experiment tested Panzeeâs ability to generalize across both familiar and novel talkers, a perceptually challenging task that humans seem to perform effortlessly.
Panzeeâs performance was similar to that of humans in all experiments. In Experiment 1, results demonstrated that Panzee likely attends to the same âspectro-temporalâ cues in sine-wave and noise-vocoded speech that humans are sensitive to. In Experiment 2, Panzee showed a similar intelligibility pattern as a function of reversal-window length as found in human listeners. In Experiment 3, Panzee readily recognized words not only from a variety of familiar adult males and females, but also from unfamiliar adults and children of both sexes. Overall, results suggest that a combination of general auditory processing and sufficient exposure to meaningful spoken language is sufficient to account for speech-perception evidence previously proposed to require specialized, uniquely human mechanisms. These findings in turn suggest that speech-perception capabilities were already present in latent form in the common evolutionary ancestors of modern chimpanzees and humans
Comparative Economics: Responses to the Assurance Game in Monkeys, Apes, and Humans Using Equivalent Procedures
There is great interest in the evolution of economic behavior. In typical studies, species are asked to play one of a series of economic games, derived from game theory, and their responses are compared. The advantage of this approach is the relative level of consistency and control that emerges from the games themselves; however in the typical experiment, procedures and conditions differ widely, particularly between humans and other species. Thus, in the current study we investigated how three primate species, capuchin monkeys, chimpanzees, and humans, played the Assurance (or Stag Hunt) Game using procedures which were, to the best of our ability, the same across species, particularly with respect to training and pre-testing. Our goal was to determine what, if any, differences existed in the ways in which these species made decisions in this game. We hypothesized differences along phylogenetic lines, which we found. However, the species were more similar than might be expected. In particular, humans who played using ânon-human primate-friendlyâ rules did not behave as is typical. Thus, we find evidence for similarity in decision-making processes across the Order Primates. These results indicate that such comparative studies are possible and moreover that in any comparison rating speciesâ relative abilities, extreme care must be taken in ensuring that one species does not have an advantage over the others due to methodological procedures
Responses to the Assurance Game in Monkeys, Apes, and Humans Using Equivalent Procedures
There is great interest in the evolution of economic behavior. In typical studies, species are asked to play one of a series of economic games, derived from game theory, and their responses are compared. The advantage of this approach is the relative level of consistency and control that emerges from the games themselves; however, in the typical experiment, procedures and conditions differ widely, particularly between humans and other species. Thus, in the current study, we investigated how three primate species, capuchin monkeys, chimpanzees, and humans, played the Assurance (or Stag Hunt) game using procedures that were, to the best of our ability, the same across species, particularly with respect to training and pretesting. Our goal was to determine what, if any, differences existed in the ways in which these species made decisions in this game. We hypothesized differences along phylogenetic lines, which we found. However, the species were more similar than might be expected. In particular, humans who played using ânonhuman primate-friendlyâ rules did not behave as is typical. Thus, we find evidence for similarity in decision-making processes across the order Primates. These results indicate that such comparative studies are possible and, moreover, that in any comparison rating speciesâ relative abilities, extreme care must be taken in ensuring that one species does not have an advantage over the others due to methodological procedures
The language faculty that wasn't : a usage-based account of natural language recursion
In the generative tradition, the language faculty has been shrinkingâperhaps to include only the mechanism of recursion. This paper argues that even this view of the language faculty is too expansive. We first argue that a language faculty is difficult to reconcile with evolutionary considerations. We then focus on recursion as a detailed case study, arguing that our ability to process recursive structure does not rely on recursion as a property of the grammar, but instead emerges gradually by piggybacking on domain-general sequence learning abilities. Evidence from genetics, comparative work on non-human primates, and cognitive neuroscience suggests that humans have evolved complex sequence learning skills, which were subsequently pressed into service to accommodate language. Constraints on sequence learning therefore have played an important role in shaping the cultural evolution of linguistic structure, including our limited abilities for processing recursive structure. Finally, we re-evaluate some of the key considerations that have often been taken to require the postulation of a language faculty
Exclusion Performance in Dwarf Goats (Capra aegagrus hircus) and Sheep (Ovis orientalis aries)
Using a comparative approach, we investigated the ability of dwarf goats and sheep to use direct and indirect information about the location of a food reward in an object-choice task. Subjects had to choose between two cups with only one covering a reward. Before making a choice, subjects received information about the baited (direct information) or non-baited cup (indirect information). Both goats and sheep were able to use direct information (presence of food) in the object choice task. After controlling for local enhancement, we found that goats rather than sheep were able to use indirect information (i.e., the absence of food) to find a reward. The actual test setup could not clarify whether individual goats were able to inferentially reason about the content of the baited cup when only shown the content of the non-baited cup or if they simply avoided the empty cup in that situation. As browsing species, feral and wild goats exhibit highly selective feeding behaviour compared to the rather unselective grazing sheep. The potential influence of this species-specific foraging flexibility of goats and sheep for using direct and indirect information to find a food reward is discussed in relation to a higher aversion to losses in food acquisition in goats compared to sheep
Editors' introduction: Aligning implicit learning and statistical learning: Two approaches, one phenomenon
In their editorsâ introduction, Rebuschat and Monaghan provide the background to the special issue. They outline the rationale for bringing together, in a single volume, leading researchers from two distinct, yet related research strands,implicit learning and statistical learning. The editors then introduce the new contributions solicited for this special issueand provide their perspective on the agenda setting that results from combining these two approaches
Perception of Synthetic Speech by a Language-Trained Chimpanzee (Pan troglodytes)
Ability of human listeners to understand altered speech is argued as evidence of uniquely human processing abilities, but early auditory experience also may contribute to this capability. I tested the ability of Panzee, a language-trained chimpanzee (Pan troglodytes), reared and spoken to from infancy by humans, to recognize synthesized words. Training and testing was conducted with different sets of English words in natural, âharmonics-onlyâ (resynthesized using only voiced components), or ânoise-vocodedâ (based on amplitude-modulated noise bands) forms, with Panzee choosing from âlexigramâ symbols that represented words. In Experiment 1 performance was equivalent with words in natural and harmonics-only form. In Experiment 2 performance with noise-vocoded words was significantly higher than chance but lower than with natural words. Results suggest specialized processing mechanisms are not necessary to speech perception in the absence of traditional acoustic cues, with the more important factor for speech-processing abilities being early immersion in a speech-rich environment
A Chimpanzeeâs (Pan troglodytes) Perception of Variations in Speech: Identification of Familiar Words when Whispered and When Spoken by a Variety of Talkers
Correlational matrices for Sherman and Lana comparing performance (Known or Not Known) between all pairs of years for all words that were tested.
<p>Note. All correlations were statistically significant, <i>p</i> < .01. The df for correlations that included years 1999â2003 was 184. The df for correlations that only included years 2004â2008 was 198.</p><p>Correlational matrices for Sherman and Lana comparing performance (Known or Not Known) between all pairs of years for all words that were tested.</p
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A Chimpanzeeâs (Pan troglodytes) Perception of Variations in Speech: Identification of Familiar Words when Whispered and When Spoken by a Variety of Talkers
When humans perceive speech they process the acoustic properties of the sounds. The acoustics of a specific word can be different depending on who produces it and how they produce it. For example, a whispered word has different acoustic properties than a word spoken in a more natural manner; basically, the acoustics are ânoisier.â A word will also sound differently depending on who speaks it, due to the different physical and physiological characteristics of the talker. In this instance, humans routinely normalize speech to retrieve the lexical meaning by solving what is termed the âlack of invarianceâ problem. We investigated these speech perception phenomena in a language-trained chimpanzee (Pan troglodytes) named Panzee to ascertain if more generalized auditory capabilities, as opposed to specialized human cognitive processes, were adequate to accomplish these perceptual tasks. In Experiment 1 we compared the chimpanzeeâs performance when identifying words she was familiar with in natural versus whispered form. In Experiment 2 we investigated Panzeeâs ability to solve the âlack of invarianceâ problem when familiar words were spoken by a variety of talkers (familiar and unfamiliar male and female adults, and children). The results of Experiment 1 demonstrated that there was no difference in her recognition for the two word types. The results of Experiment 2 revealed no significant difference in Panzeeâs performance across all talker types. Her overall performance suggests that more generalized capabilities are sufficient for solving for uncertainty when processing the acoustics of speech, and instead favor a strong role of early experience