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Visual recognition of age class and preference for infantile features: implications for species-specific vs universal cognitive traits in primates.

Sato A, Koda H, Lemasson A, Nagumo S, Masataka N - PLoS ONE (2012)

Bottom Line: When analyzing the side of the first look, JM subjects significantly looked more often at novel images.CM subjects showed no difference in the side of their first look, but looked at infant JM images longer than they looked at adult images; the fact that CMs were totally naïve to JMs suggested that the attractiveness of infant images transcends species differences.Our results suggest not only species-specific processing for age class recognition but also the evolutionary origins of the instinctive human perception of baby cuteness schema, proposed by the ethologist Konrad Lorenz.

View Article: PubMed Central - PubMed

Affiliation: Primate Research Institute, Kyoto University, Inuyama, Aichi, Japan.

ABSTRACT
Despite not knowing the exact age of individuals, humans can estimate their rough age using age-related physical features. Nonhuman primates show some age-related physical features; however, the cognitive traits underlying their recognition of age class have not been revealed. Here, we tested the ability of two species of Old World monkey, Japanese macaques (JM) and Campbell's monkeys (CM), to spontaneously discriminate age classes using visual paired comparison (VPC) tasks based on the two distinct categories of infant and adult images. First, VPCs were conducted in JM subjects using conspecific JM stimuli. When analyzing the side of the first look, JM subjects significantly looked more often at novel images. Based on analyses of total looking durations, JM subjects looked at a novel infant image longer than they looked at a familiar adult image, suggesting the ability to spontaneously discriminate between the two age classes and a preference for infant over adult images. Next, VPCs were tested in CM subjects using heterospecific JM stimuli. CM subjects showed no difference in the side of their first look, but looked at infant JM images longer than they looked at adult images; the fact that CMs were totally naïve to JMs suggested that the attractiveness of infant images transcends species differences. This is the first report of visual age class recognition and a preference for infant over adult images in nonhuman primates. Our results suggest not only species-specific processing for age class recognition but also the evolutionary origins of the instinctive human perception of baby cuteness schema, proposed by the ethologist Konrad Lorenz.

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Related in: MedlinePlus

First look sides (FLs) for the stimulus novelty and order conditions in 40 trials of 10 Campbell's monkeys. In the AI condition, the adult image was used as the stimulus in the familiar phase and the infant image served as the novel stimulus in the test phase. In the IA condition, the infant image was used as the stimulus in the familiar phase and the adult imaged served as the novel stimulus in the test phase. Black bars, FLs for familiar stimuli; white bars, FLs for novel stimuli.
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pone-0038387-g004: First look sides (FLs) for the stimulus novelty and order conditions in 40 trials of 10 Campbell's monkeys. In the AI condition, the adult image was used as the stimulus in the familiar phase and the infant image served as the novel stimulus in the test phase. In the IA condition, the infant image was used as the stimulus in the familiar phase and the adult imaged served as the novel stimulus in the test phase. Black bars, FLs for familiar stimuli; white bars, FLs for novel stimuli.

Mentions: In Experiment 2, CMs were presented with the same JM image stimuli in the VPC tasks. Figure 4 shows the side of the first look in the two order conditions in Experiment 2. The occurrences of FLs for novel stimulus were the same with those for familiar stimulus, in both IA and AI conditions, indicating that FLs of CM subjects were not influenced by the stimulus category in the familiarization phase. This FL results would suggest that CM, conversely to JM, were unable to discriminate visually between the different age classes. However, LT in CM subject showed different patterns from FL results. Figure 5 shows the LTs for the novel and familiar stimuli in the two order conditions. No significant main effect was found for novelty (F1,38 = 2.56, P = 0.118) and order condition (F1,29 = 0.116, P = 0.736); however, a significant interaction effect was found between the novelty category and order condition (F1,38 = 10.67, P = 0.0023), indicating that the effect of novelty differed between the AI and IA conditions. The analysis of parameter coefficients in the GLMM revealed that the LT for the novel image was significantly longer than that for the familiar image in the AI condition, whereas no difference in LT was found in the IA condition (Figure 5, Table 2). This shows that in CM subjects, the LT for the novel stimulus was significantly longer than that for the familiar stimulus only when the novel stimulus was the infant image. These results are similar to those of the JMs, even though the stimuli depicted a completely unfamiliar species. The analysis of parameter coefficients in the GLMM also revealed that the LT for the novel image in AI condition (here, infant image) was significantly longer than those in the IA condition (adult), whereas LT for the familiar image in AI condition (adult) was significantly shorter than those in the AI condition (infant; see Figure 5, Table 2). This suggested that CM likely looked at infant images regardless of the stimulus category in the familiarization phase. The finding that CMs looked at infant images significantly longer than adult images suggests that CM subjects, like JMs, preferred to look at unfamiliar heterospecific JM infant images over JM adult images.


Visual recognition of age class and preference for infantile features: implications for species-specific vs universal cognitive traits in primates.

Sato A, Koda H, Lemasson A, Nagumo S, Masataka N - PLoS ONE (2012)

First look sides (FLs) for the stimulus novelty and order conditions in 40 trials of 10 Campbell's monkeys. In the AI condition, the adult image was used as the stimulus in the familiar phase and the infant image served as the novel stimulus in the test phase. In the IA condition, the infant image was used as the stimulus in the familiar phase and the adult imaged served as the novel stimulus in the test phase. Black bars, FLs for familiar stimuli; white bars, FLs for novel stimuli.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3368701&req=5

pone-0038387-g004: First look sides (FLs) for the stimulus novelty and order conditions in 40 trials of 10 Campbell's monkeys. In the AI condition, the adult image was used as the stimulus in the familiar phase and the infant image served as the novel stimulus in the test phase. In the IA condition, the infant image was used as the stimulus in the familiar phase and the adult imaged served as the novel stimulus in the test phase. Black bars, FLs for familiar stimuli; white bars, FLs for novel stimuli.
Mentions: In Experiment 2, CMs were presented with the same JM image stimuli in the VPC tasks. Figure 4 shows the side of the first look in the two order conditions in Experiment 2. The occurrences of FLs for novel stimulus were the same with those for familiar stimulus, in both IA and AI conditions, indicating that FLs of CM subjects were not influenced by the stimulus category in the familiarization phase. This FL results would suggest that CM, conversely to JM, were unable to discriminate visually between the different age classes. However, LT in CM subject showed different patterns from FL results. Figure 5 shows the LTs for the novel and familiar stimuli in the two order conditions. No significant main effect was found for novelty (F1,38 = 2.56, P = 0.118) and order condition (F1,29 = 0.116, P = 0.736); however, a significant interaction effect was found between the novelty category and order condition (F1,38 = 10.67, P = 0.0023), indicating that the effect of novelty differed between the AI and IA conditions. The analysis of parameter coefficients in the GLMM revealed that the LT for the novel image was significantly longer than that for the familiar image in the AI condition, whereas no difference in LT was found in the IA condition (Figure 5, Table 2). This shows that in CM subjects, the LT for the novel stimulus was significantly longer than that for the familiar stimulus only when the novel stimulus was the infant image. These results are similar to those of the JMs, even though the stimuli depicted a completely unfamiliar species. The analysis of parameter coefficients in the GLMM also revealed that the LT for the novel image in AI condition (here, infant image) was significantly longer than those in the IA condition (adult), whereas LT for the familiar image in AI condition (adult) was significantly shorter than those in the AI condition (infant; see Figure 5, Table 2). This suggested that CM likely looked at infant images regardless of the stimulus category in the familiarization phase. The finding that CMs looked at infant images significantly longer than adult images suggests that CM subjects, like JMs, preferred to look at unfamiliar heterospecific JM infant images over JM adult images.

Bottom Line: When analyzing the side of the first look, JM subjects significantly looked more often at novel images.CM subjects showed no difference in the side of their first look, but looked at infant JM images longer than they looked at adult images; the fact that CMs were totally naïve to JMs suggested that the attractiveness of infant images transcends species differences.Our results suggest not only species-specific processing for age class recognition but also the evolutionary origins of the instinctive human perception of baby cuteness schema, proposed by the ethologist Konrad Lorenz.

View Article: PubMed Central - PubMed

Affiliation: Primate Research Institute, Kyoto University, Inuyama, Aichi, Japan.

ABSTRACT
Despite not knowing the exact age of individuals, humans can estimate their rough age using age-related physical features. Nonhuman primates show some age-related physical features; however, the cognitive traits underlying their recognition of age class have not been revealed. Here, we tested the ability of two species of Old World monkey, Japanese macaques (JM) and Campbell's monkeys (CM), to spontaneously discriminate age classes using visual paired comparison (VPC) tasks based on the two distinct categories of infant and adult images. First, VPCs were conducted in JM subjects using conspecific JM stimuli. When analyzing the side of the first look, JM subjects significantly looked more often at novel images. Based on analyses of total looking durations, JM subjects looked at a novel infant image longer than they looked at a familiar adult image, suggesting the ability to spontaneously discriminate between the two age classes and a preference for infant over adult images. Next, VPCs were tested in CM subjects using heterospecific JM stimuli. CM subjects showed no difference in the side of their first look, but looked at infant JM images longer than they looked at adult images; the fact that CMs were totally naïve to JMs suggested that the attractiveness of infant images transcends species differences. This is the first report of visual age class recognition and a preference for infant over adult images in nonhuman primates. Our results suggest not only species-specific processing for age class recognition but also the evolutionary origins of the instinctive human perception of baby cuteness schema, proposed by the ethologist Konrad Lorenz.

Show MeSH
Related in: MedlinePlus