Figure 4.

Exchanging the pellets during a progressive ratio (PR) session leads to an increase in motivation in rats conditioned with chow but pressing for sucrose. Rats conditioned with sucrose but pressing for chow do not show a different motivation. A, Number of earned pellets; B, number of active lever presses; C, response ratio; D, inactive lever presses; E, total activity; F, 24 h chow diet intake. Data are shown as the mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001. Chow‐conditioned rats, n = 24; sucrose‐conditioned rats, n = 23