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Large number discrimination by mosquitofish.

Agrillo C, Piffer L, Bisazza A - PLoS ONE (2010)

Bottom Line: Fish proved to be able to discriminate up to 100 vs. 200 objects, without showing any significant decrease in accuracy compared with the 4 vs. 8 discrimination.Performance was found to decrease when decreasing the numerical distance.As observed in human and non-human primates, the numerical system of fish appears to have virtually no upper limit while the numerical ratio has a clear effect on performance.

View Article: PubMed Central - PubMed

Affiliation: Department of General Psychology, University of Padova, Padova, Italy. christian.agrillo@unipd.it

ABSTRACT

Background: Recent studies have demonstrated that fish display rudimentary numerical abilities similar to those observed in mammals and birds. The mechanisms underlying the discrimination of small quantities (<4) were recently investigated while, to date, no study has examined the discrimination of large numerosities in fish.

Methodology/principal findings: Subjects were trained to discriminate between two sets of small geometric figures using social reinforcement. In the first experiment mosquitofish were required to discriminate 4 from 8 objects with or without experimental control of the continuous variables that co-vary with number (area, space, density, total luminance). Results showed that fish can use the sole numerical information to compare quantities but that they preferentially use cumulative surface area as a proxy of the number when this information is available. A second experiment investigated the influence of the total number of elements to discriminate large quantities. Fish proved to be able to discriminate up to 100 vs. 200 objects, without showing any significant decrease in accuracy compared with the 4 vs. 8 discrimination. The third experiment investigated the influence of the ratio between the numerosities. Performance was found to decrease when decreasing the numerical distance. Fish were able to discriminate numbers when ratios were 1:2 or 2:3 but not when the ratio was 3:4. The performance of a sample of undergraduate students, tested non-verbally using the same sets of stimuli, largely overlapped that of fish.

Conclusions/significance: Fish are able to use pure numerical information when discriminating between quantities larger than 4 units. As observed in human and non-human primates, the numerical system of fish appears to have virtually no upper limit while the numerical ratio has a clear effect on performance. These similarities further reinforce the view of a common origin of non-verbal numerical systems in all vertebrates.

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Results of Experiment 1a.Accuracy when luminance, density, overall space and cumulative surface area were controlled. Fish performance dropped to chance level only when cumulative surface area was paired (*  =  p < 0.05; **  =  p < 0.01).
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pone-0015232-g001: Results of Experiment 1a.Accuracy when luminance, density, overall space and cumulative surface area were controlled. Fish performance dropped to chance level only when cumulative surface area was paired (*  =  p < 0.05; **  =  p < 0.01).

Mentions: All ten subjects reached the learning criterion in the training phase. We reported no difference in the accuracy (proportion of correct choices) between fish trained with 8 (mean ± std. dev.: 0.753±0.556) and those trained with 4 figures as positive (0.796±0.071; independent t-test t(8)  =  −1.06, p = 0.319). In the test phase significant discrimination was observed when no continuous variable was controlled (one sample t-test t(9)  = 7.97, p<0.001), when total brightness (t(9)  = 6.09, p<0.001), density (t(9)  = 6.13, p<0.001) and overall space occupied by the arrays (t(9)  = 3.0, p = 0.015) were singly controlled. On the contrary, no significant choice toward the trained quantity was found when cumulative surface area was controlled (t(9)  = 0.17, p = 0.872, Fig. 1) suggesting that this latter cue had been used by the subjects during the learning phase.


Large number discrimination by mosquitofish.

Agrillo C, Piffer L, Bisazza A - PLoS ONE (2010)

Results of Experiment 1a.Accuracy when luminance, density, overall space and cumulative surface area were controlled. Fish performance dropped to chance level only when cumulative surface area was paired (*  =  p < 0.05; **  =  p < 0.01).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3008722&req=5

pone-0015232-g001: Results of Experiment 1a.Accuracy when luminance, density, overall space and cumulative surface area were controlled. Fish performance dropped to chance level only when cumulative surface area was paired (*  =  p < 0.05; **  =  p < 0.01).
Mentions: All ten subjects reached the learning criterion in the training phase. We reported no difference in the accuracy (proportion of correct choices) between fish trained with 8 (mean ± std. dev.: 0.753±0.556) and those trained with 4 figures as positive (0.796±0.071; independent t-test t(8)  =  −1.06, p = 0.319). In the test phase significant discrimination was observed when no continuous variable was controlled (one sample t-test t(9)  = 7.97, p<0.001), when total brightness (t(9)  = 6.09, p<0.001), density (t(9)  = 6.13, p<0.001) and overall space occupied by the arrays (t(9)  = 3.0, p = 0.015) were singly controlled. On the contrary, no significant choice toward the trained quantity was found when cumulative surface area was controlled (t(9)  = 0.17, p = 0.872, Fig. 1) suggesting that this latter cue had been used by the subjects during the learning phase.

Bottom Line: Fish proved to be able to discriminate up to 100 vs. 200 objects, without showing any significant decrease in accuracy compared with the 4 vs. 8 discrimination.Performance was found to decrease when decreasing the numerical distance.As observed in human and non-human primates, the numerical system of fish appears to have virtually no upper limit while the numerical ratio has a clear effect on performance.

View Article: PubMed Central - PubMed

Affiliation: Department of General Psychology, University of Padova, Padova, Italy. christian.agrillo@unipd.it

ABSTRACT

Background: Recent studies have demonstrated that fish display rudimentary numerical abilities similar to those observed in mammals and birds. The mechanisms underlying the discrimination of small quantities (<4) were recently investigated while, to date, no study has examined the discrimination of large numerosities in fish.

Methodology/principal findings: Subjects were trained to discriminate between two sets of small geometric figures using social reinforcement. In the first experiment mosquitofish were required to discriminate 4 from 8 objects with or without experimental control of the continuous variables that co-vary with number (area, space, density, total luminance). Results showed that fish can use the sole numerical information to compare quantities but that they preferentially use cumulative surface area as a proxy of the number when this information is available. A second experiment investigated the influence of the total number of elements to discriminate large quantities. Fish proved to be able to discriminate up to 100 vs. 200 objects, without showing any significant decrease in accuracy compared with the 4 vs. 8 discrimination. The third experiment investigated the influence of the ratio between the numerosities. Performance was found to decrease when decreasing the numerical distance. Fish were able to discriminate numbers when ratios were 1:2 or 2:3 but not when the ratio was 3:4. The performance of a sample of undergraduate students, tested non-verbally using the same sets of stimuli, largely overlapped that of fish.

Conclusions/significance: Fish are able to use pure numerical information when discriminating between quantities larger than 4 units. As observed in human and non-human primates, the numerical system of fish appears to have virtually no upper limit while the numerical ratio has a clear effect on performance. These similarities further reinforce the view of a common origin of non-verbal numerical systems in all vertebrates.

Show MeSH