Norman, Price and Duff (2006) found that scores on the openness/feeling scale of NEO-PI-R could predict performance on deterministic implicit sequence learning. In another study, no such correlation was identified in complex probabilistic implicit sequence learning (Norman, Price, Duff, & Mentzoni, 2007). However, Kaufman, et al. (2010) found that performance on probabilistic implicit sequence learning was significantly related to the openness scale (i.e., it includes four dimensions of aesthetics, imagination, feeling and plot) of NEO-PI-R. The researchers concluded that implicit learning might be relate to experience openness rather than to feeling openness. In the present study, by adopting Norman, et al.’ experimental design (2007), but with fewer blocks (11 blocks) and more response stimulus intervals (5 RSIs), it was found that scores on the openness/feeling scale could predict performance on probabilistic implicit sequence learning. Specifically, individuals with high vs. low openness/feeling tend to show significant differences in implicit gradient process. In Experiment 1, a complex probabilistic implicit sequence learning procedure (Norman, et al., 2007) was used. There were two sequences in the training stage. One was probable sequence (SOC1 or SOC2) with a probability of 0.88, The other was improbable sequence (SOC2 or SOC1) with the probability of 0.12. For the experimental group, a 2 (high vs. low openness/feeling group) × 2 (probable vs. improbable sequence) × 11 (block) mixed design was used. The procedure for the experimental group was consisted of a training phase, a recognition phase, and a generation test phase (the generation test includes both a contain task and a rotation task). Each openness/feeling group was consisted of 38 subjects. For the control group, a 2 (high vs. low openness/feeling group) × 11 (block) mixed design was used. The control group was asked to study a random sequence and received only a training phase. In experiment 2, a 2 (high vs. low openness/feeling group) × 4 (RSI: 0 ms, 250 ms, 750 ms, 1000 ms) × 2 (probable vs. improbable sequence) × 11 (block) mixed design was used. Numbers of subjects for each openness/feeling group were around 20. The experimental process was the same as the experiment 1. No significant reaction time decrement was found in the control group in experiment 1. Therefore, reaction time decrement was used as an indicator of implicit learning for the experimental group. It was found that, when RSI was 500 ms, both high and low openness/feeling groups could learn probable sequence, but only high openness/feeling group eventually acquired improbable sequence. In experiment 2, When RSI was smaller than 500ms, high openness/feeling group failed to acquire either probable or improbable sequence before transfer block 9, but acquire both after transfer block 9. When RSI was greater than or equal to 500ms, high openness/feeling group acquired probable sequence before transfer block 9 and improbable sequence after transfer block 9. In contrast, low openness/feeling group could acquire probable sequence before transfer block 9 in all RSIs, but failed to learn improbable sequence regardless of RSI setting. Different from previous researchs, significant block reaction time differences (i.e., between transfer block 9 and block 8, as well as between transfer block 9 and block 10) used as the amount of implicit learning in previous researchs were not detected for the high and low openness/feeling groups in all RSIs, except for low openness/feeling group in RSI -0 ms. And surprisingly, in all RSIs, participants’ scores for recognition, contain task and rotation tasks were at or below the random level. Low openness/feeling group performed significantly better than high openness/feeling group in recognition task when RSI was 750 ms and rotation task when RSI was 500 ms. Results from the two experiments proved that scores on the openness/feeling scale of NEO-PI-R can predict individual differences in probabilistic implicit sequence learning. Essential differences between high and low openness/feeling groups exist in implicit acquisition process of probable and improbable sequences along with the increase of the RSI. High openness/feeling group could learn probable and improbable sequences by using collateral elaboration, but low openness/feeling group could only learn probable sequence. For studying implicit learning and individual differences in probabilistic implicit sequence learning, improbable sequence leaning can be a sensitive measure, while other measures such as transfer block, recognition task, and generation task are limited in terms of their predictability because of the interference of improbable sequence learning.
