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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 4.Adult humans were required to make numerical judgements with the same stimuli used in experiment 2. Both accuracy (graph a) and reaction time (ms, graph b) were not affected by total numerosity (Circles: stimuli controlled for continuous variables; squares: number and continuous variables available).
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pone-0015232-g003: Results of Experiment 4.Adult humans were required to make numerical judgements with the same stimuli used in experiment 2. Both accuracy (graph a) and reaction time (ms, graph b) were not affected by total numerosity (Circles: stimuli controlled for continuous variables; squares: number and continuous variables available).

Mentions: As regards the influence of the total number of elements to discriminate, accuracy and reaction time were analyzed separately by the 3×2 repeated measure ANOVA, with ‘Total numerosity’ (4 vs. 8, 15 vs. 30 and 100 vs. 200) and ‘Control of continuous variables’ (controlled/non-controlled) as within-subject factors. There was no effect of total numerosity or control of continuous variables on accuracy (Total numerosity: F(2,48)  = 2.29, p = 0.113; Control of continuous variables F(1,48)  = 2.09, p = 0.161). However, a significant interaction between the two factors was observed (F(2,48)  = 5.10, p = 0.010, Fig. 3.a), since accuracy slightly increased with increasing the number of elements in presentations not controlled for continuous variables, while it tended to decrease when participants were prevented from using continuous variables. When controlled and non-controlled presentations were analyzed separately, we found no significant effect of total numerosity in non-controlled presentations (repeated measure ANOVA F(2,48)  = 2.06, p = 0.139) while there was a significant decrease of accuracy with increasing total numerosity in controlled presentations (ANOVA F(2,48)  = 4.81, p = 0.012) due to a difference between the 15 vs. 30 and the 100 vs. 200 conditions (Bonferroni post hoc test, p = 0.014).


Large number discrimination by mosquitofish.

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

Results of Experiment 4.Adult humans were required to make numerical judgements with the same stimuli used in experiment 2. Both accuracy (graph a) and reaction time (ms, graph b) were not affected by total numerosity (Circles: stimuli controlled for continuous variables; squares: number and continuous variables available).
© Copyright Policy
Related In: Results  -  Collection

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

pone-0015232-g003: Results of Experiment 4.Adult humans were required to make numerical judgements with the same stimuli used in experiment 2. Both accuracy (graph a) and reaction time (ms, graph b) were not affected by total numerosity (Circles: stimuli controlled for continuous variables; squares: number and continuous variables available).
Mentions: As regards the influence of the total number of elements to discriminate, accuracy and reaction time were analyzed separately by the 3×2 repeated measure ANOVA, with ‘Total numerosity’ (4 vs. 8, 15 vs. 30 and 100 vs. 200) and ‘Control of continuous variables’ (controlled/non-controlled) as within-subject factors. There was no effect of total numerosity or control of continuous variables on accuracy (Total numerosity: F(2,48)  = 2.29, p = 0.113; Control of continuous variables F(1,48)  = 2.09, p = 0.161). However, a significant interaction between the two factors was observed (F(2,48)  = 5.10, p = 0.010, Fig. 3.a), since accuracy slightly increased with increasing the number of elements in presentations not controlled for continuous variables, while it tended to decrease when participants were prevented from using continuous variables. When controlled and non-controlled presentations were analyzed separately, we found no significant effect of total numerosity in non-controlled presentations (repeated measure ANOVA F(2,48)  = 2.06, p = 0.139) while there was a significant decrease of accuracy with increasing total numerosity in controlled presentations (ANOVA F(2,48)  = 4.81, p = 0.012) due to a difference between the 15 vs. 30 and the 100 vs. 200 conditions (Bonferroni post hoc test, p = 0.014).

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