Int. J. Environ. Res. Public Health 2009, 6 2016 (p = 0.001), blocks 1 and 6 (p = 0.002), and marginal significance between blocks 1 and 5 (p = 0.06) during delay conditioning. The learning curve for trace conditioning was similar, although acquisition was not as strong as in trace conditioning. T-tests confirmed significant differences between blocks 1 and 2 (p = 0.01), blocks 1 and 3 (p = 0.007), blocks 1 and 4 (p = 0.005), blocks 1 and 6 (p = 0.005), and marginal significance between blocks 1 and 5 (p = 0.06). Block by block comparisons between paradigms revealed a significant difference in CR production during reinforced trials at block four (t = 2.49; p = 0.02). Percentage of CRs on nonreinforced trials remained stable across learning blocks in both paradigms. Block by block comparisons showed no difference in CR production during nonreinforced trials between paradigms. Overall, Figure 3 reveals that alcoholics attained some level of differential learning during both delay and trace discrimination, although acquisition was greater during delay conditioning. Response Latency & Amplitude Independent samples T-tests of CR response latency during reinforced trials revealed that none of the measures differed significantly between paradigms (p’s > 0.07) during discrimination learning (see Table 2). Similarly, there were no differences between paradigms for CR or UR amplitude during discrimination learning (p’s > 0.50) (see Table 2). Table 2. Conditioned Response Measure Means (standard deviation) and Unconditioned Response Measure Means (standard deviation). Discrimination Reversal Delay Trace Delay Trace CR Onset Latency CR Peak Latency CR Amplitude UR Amplitude CS+ 880 ms (89) 851 ms (231) CS+ 900 ms (106) 865 ms (247) CS- 802 ms (283) 936 ms (96) CS- 903 ms (91) 790 ms (305) CS+ CS- CS+ 1,006 894 ms 19 mV ms (61) (313) (15) 916 ms 981 ms 17 mV (249) (94) (14) CS+ CS- CS+ 1,015 990 ms 14 mV ms (75) (63) (8) 933 ms 860 ms 16 mV (268) (333) (12) CS- 16 mV (17) 16 mV (10) CS- 13 mV (5) 19 mV (18) CS+ 45 mV (16) 44 mV (16) CS+ 56 mV (20) 37 mV (15) CS- 12 mV (12) 10 mV (9) CS- 10 mV (5) 10 mV (9) 3.2. Reversal Learning Conditioned Response Acquisition During reversal learning, the previously reinforced CS+ became the CS-, and the previously nonreinforced CS- became the CS+ requiring participants to flexibly alter their previously learned