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Percentage of correct answers

An exact binomial test with exact Clopper-Pearson 95% confidence intervals (CI) was used for each individual turtle and condition to determine if the turtles chose a greater proportion of reinforced or non-reinforced colours. Out of the 6 individuals, all could significantly discriminate between red and blue and scored above 85% of correct choices (Fig. 1).

Fig. 1: The overall percentage of correct choices made by the six individual turtles. The colours of the columns illustrate their reinforced colour. The error bars indicate the Clopper-Pearson 95% confidence intervals and the asterisks signal marks significance with a single asterisk (*) indicating significance at p < 0.05 and a double asterisk (**) indicating significance at p < 0.01.

Turtle 1 was also tested using three targets, two with the incorrect and one with the correct colour. Statistically, this would provide a higher certainty that the turtle was not choosing the reinforced colour only by chance. While using three targets, turtle 1 chose the reinforced colour 99.5% of the time (n = 42, p < 0.01).

Comparison between colour groups

After confirming that the data was normally distributed an independent t-test showed there were no significant differences (t(2.65) = 1.075, p-value = 0.37) between the red group (x̄ = 93.81%, SD = 5.87) and the blue group (x̄ = 97.75%, SD = 2.39).

Learning speed

The turtles needed a median of 7.5 sessions and 62.5 trials to meet the learning criterion (SD = 1.32, range of 37 – 81 trials, Fig. 2 & 3). No statistical analysis could be done to determine whether there was a significant difference between the turtles that had red as a rewarded colour and those that had blue.    

Fig. 2: The speed at which the turtles with blue as the correct colour learned to discriminate between the two colours. Session 1 is the first day the turtles were shown both colours. The learning criterion was met when each turtle made 10 correct choices for two consecutive sessions.
Fig. 3: The speed at which the turtles with red as the correct colour learned to discriminate between the two colours. Session 1 is the first day the turtles were shown both colours. The learning criterion was met when each turtle made 10 correct choices for two consecutive sessions.

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