Fig 1.
Trial design for Experiment 1.
A) SRT-AGL task. On each trial participants were presented with an array of 6 visual nonsense word stimuli. Every trial contained 2 ‘A’ elements in the left column, 2 ‘X’ elements in the middle column, and 2 ‘B’ items in the right column. Participants were presented with an auditory cue corresponding to one of the two visual stimuli in each column, and were asked to click on the matching visual stimulus as quickly as possible (see Methods). Following their final response, participants were given a score corresponding to their total reaction time across the whole sequence. B) Sequence Completion task. As in the SRT-AGL task, participants were presented with a visual array of stimuli and responded to the first two auditory cue stimuli. However, the final auditory cue stimulus was replaced with a ‘beep’ sound, and the participants were asked to guess the nonsense word stimulus that they felt completed the sequence. C) Grammaticality Judgement Task. In this task participants were shown a blue fixation spot and were presented with an auditory sequence that was either ‘grammatical’ or ‘ungrammatical’. When the spot changed colour, they pressed one of two keys on the keyboard to indicate whether the sequence followed the same pattern as the sequence they had heard previously or not.
Table 1.
Sequences all took the form ‘AXB’ (e.g., ‘bek kiv jat’), in which the ‘A’ and ‘B’ elements always co-occurred. There were 3 ‘A’ and ‘B’ elements and 24 possible ‘X’ elements giving a total of 72 possible grammatical sequences. Each sequence was presented once in each Learning Block and in the Recovery Block (see Methods). In the Testing Block, ungrammatical pairs of A and B elements (i.e., A1_B2, A1_B3, A2_B1, A2_B3, A3_B1, A3_B2) were presented four times and each ‘X’ element was presented once.
Fig 2.
A) Mean reaction time differences (RTA-B ± SEM, thick blue line) for all participants for the 6 Learning Blocks, the Testing Block containing ungrammatical sequences (highlighted in pink), and the Recovery Block. Individual data is shown in grey. B) Mean (± SEM) performance on the sequence completion task. Individual performance is shown in circles. Good learners are shown in green (based on individual binomial tests, p < 0.05), non-learners are shown in red (p > 0.05). C) Mean performance (± SEM) on the grammaticality judgement task, including learners and non-learners, as in B. D) Mean reaction time differences (RTA-B ± SEM) highlighting the good learners (green) based on the sequence completion and grammaticality judgement tasks, showing the predicted pattern of responses. E) Mean reaction time differences (RTA-B ± SEM) for the non-learners (red) on the sequence completion and grammaticality judgement tasks, showing no learning on the SRT-AGL task.
Fig 3.
The ‘A’, ‘B’ and ‘X’ elements corresponded to plants, foods and animals respectively. The ‘A’ and ‘B’ elements always co-occurred, and sequences were presented in the form ‘AXB’ (e.g., ‘tree cat bread’). There are 3 ‘A’ and ‘B’ elements and 24 possible ‘X’ elements giving a total of 72 possible grammatical sequences. Each sequence was presented once in each Learning and Recovery Block (see Methods).
Fig 4.
A) Mean reaction time differences (RTA-B ± SEM, thick blue line) for the 6 Learning Blocks, the Testing Block containing ungrammatical sequences (highlighted in pink), and the Recovery Block. Individual data is shown in grey. B) Mean (± SEM) performance on the sequence completion task. Individual performance is shown in circles. Good learners are shown in green (based on individual binomial tests, p < 0.05), non-learners are shown in red (p > 0.05). C) Mean performance (± SEM) on the grammaticality judgement task, including learners and non-learners, as in B. D) Mean reaction time differences (RTA-B ± SEM) highlighting the good learners based on the sequence completion and grammaticality judgement tasks, showing the predicted pattern of responses. E) Mean reaction time differences (RTA-B ± SEM) for the non-learners on the sequence completion and grammaticality judgement tasks, showing no learning on the SRT-AGL task.
Fig 5.
The ‘A’ and ‘B’ elements always co-occurred, and sequences are presented in the form ‘AXB’ in the nonadjacent version of the task, and ‘XAB’ in the adjacent version. There are 2 ‘A’ and ‘B’ elements, and 24 ‘X’ elements. 24 sequences were presented per block, with each ‘X’ element presented once per Learning Block. 20 of the sequences in each block were high frequency (e.g., A1XB1), and for the 4 low frequency sequences, the dependencies between the ‘A’ and ‘B’ elements were switched around (e.g. A1XB2; A2XB1).
Fig 6.
Trial design for Experiment 3.
A) Visual SRT-AGL task showing the nonadjacent condition (for an example of the adjacent condition, see S3 Fig in S1 File). On each trial participants were presented with an array of 6 visual abstract shapes. In the nonadjacent condition, every trial contained 2 ‘A’ elements in the left column, 2 randomly selected ‘X’ elements in the middle column, and 2 ‘B’ items in the right column. In the adjacent condition, we presented 2 randomly ‘X’ elements in the left column, 2 ‘A’ elements in the middle column, and 2 ‘B’ elements in the right column. Participants were sequentially presented with a visual cue corresponding to one of the two visual stimuli in each column, and were asked to click on the matching visual stimulus as quickly as possible (see Methods). B) Sequence Completion task. As in the SRT-AGL task, participants were presented with a visual array of stimuli and responded to the first two visual cue stimuli as before. However, the final visual cue stimulus was replaced with a question mark, and the participants were asked to guess the shape that they felt completed the sequence. C) Generation task. In each of the 24 trials, the participants were presented with 8 elements arranged in a circle on the screen: the 2 ‘A’ and ‘B’ elements were always shown, as well as 4 randomly selected, non-repeating ‘X’ elements. Participants created their sequences by clicking on the desired elements in order.
Fig 7.
Participants completed either the adjacent (A-D) or nonadjacent (E-H) task. Panels A and E show the difference in mean A—B reaction times (RTdifference ± SEM) between high and low frequency sequences across blocks in the adjacent and nonadjacent tasks respectively. Individual data is shown in grey. Panels B and F show mean (± SEM) performance in the Sequence Completion task in the adjacent and nonadjacent tasks respectively. Individual performance is shown in circles: ‘good learners’ are shown in green (based on individual binomial tests for the Grammaticality Judgement task, p < 0.05), non-learners are shown in red (p > 0.05). Panels C and G show mean performance (± SEM) on the Grammaticality Judgement task in the adjacent and nonadjacent tasks respectively. Panels D and H show mean performance (± SEM) in the Sequence Generation task in the adjacent and nonadjacent tasks respectively.