Median (1st–3rd interquartiles) of behavioural variables exhibited by each experimental group during the first three learning sessions.

<p>Median (1st–3rd interquartiles) of behavioural variables exhibited by each experimental group during the first three learning sessions.</p

Trial procedure for each learning stage.

<p>Trial procedure for each learning stage.</p

Median (1st–3rd interquartiles) of increases in salivary cortisol concentration at learning sessions 1 and 3 (differences in ng/ml).

<p>Median (1st–3rd interquartiles) of increases in salivary cortisol concentration at learning sessions 1 and 3 (differences in ng/ml).</p

Sequential screenshots of a typical learning trial from a high-angle point of view.

<p>(A) Horse is ready in the starting position. (B) Experimenter is giving stage 1 indication toward the left compartment. (C) Horse is entering the left compartment. (D) Horse has successfully entered the left compartment and is going to receive food reward in the left bucket.</p

Differences in temperament between the “low responders” and “high responders” during Pavlovian to instrumental transfer.

<p>“Low responders”: individuals who performed the fewest correct responses during CS presentation (N = 9). “High responders”: individuals who performed the most correct responses during CS presentation (N = 10).</p

Acquisition of instrumental responding in horses.

<p>S1–S4: first 4 acquisition sessions (30 trials per session). The grey bar refers to the session during which the animals reached the criterion (touching the cone in ≤15 s during 14 out of 15 consecutive trials). Depending on the individual, this session corresponds to the 1^st–6^th acquisition sessions.</p

Distal and proximal responses displayed during acquisition and reacquisition sessions.

<p>Mean number of each type of distal and proximal responses displayed during the 1st, 2nd, and 3rd blocks of the acquisition session (a) and the 4th, 5th, and 6th blocks of the reacquisition session (b) by each group. Each block consisted of 10 trials. Intra-group differences between the blocks: a vs. b vs. c, P<0.05, Wilcoxon tests.</p

Arena used for the temperament tests.

<p>Arena used for the temperament tests.</p

Apparatus used for Pavlovian conditioning (left), instrumental conditioning, and PIT sessions (right).

<p>Apparatus used for Pavlovian conditioning (left), instrumental conditioning, and PIT sessions (right).</p

Differences in temperament between the “low performers” and “high performers” during acquisition.

<p>“Low performers”: individuals who performed the fewest correct responses during the first four acquisition sessions (N = 9). “High performers”: individuals who performed the most correct responses during the first four acquisition sessions (N = 10).</p