Experimental set up and stimuli of Experiment 1

(A) Apparatus used for individual training of zebrafish larvae.

(B) The two patterns used for the learning task of Experiment 1.

Learning performance in the five days of training (from 8 to 12 dpf) of Experiment 1

Performance was calculated as preference for the reinforced stimulus in the 90-min period preceding the delivery of the food reward. For the first two days of training (group training), preference is expressed as the proportion of larvae in the compartment with the reinforced stimulus. For the remaining three days (individual training), preference is expressed as the proportion of the time that a subject spent in the compartment with the reinforced stimulus. The figure shows distinct learning curves for subjects trained using vertical bars or a dot array as positive. Data points represent mean ± SEM The black dotted line represents chance performance.

Results of Experiment 2–5

Learning curves (proportion of the time spent in the compartment with the reinforced stimulus) of zebrafish larvae in the three days of individual training of Experiment 2-5 (A: color discrimination; B: shape discrimination; C: mirror-image discrimination; D: horizontal-vertical discrimination). Data points represent mean ± SEM The dotted lines represent chance performance.

Comparison of the results of the four discrimination tasks

The boxplots report median, lower, and upper quartiles; whiskers represent values within 1.5 times the interquartile range. The asterisks (∗) denote a significant departure from chance level (one sample t-test, p < 0.05).