The present experiment evaluated Willingham & Goedert-Eschmann’s proposal (1999) that physical practice is required to support the parallel activation of explicit and implicit systems during practice of an SRT task. Individuals either physically executed or observed an individual producing a repeating 12-element sequence. Models and observers were provided with explicit information regarding the sequence or were uninformed. Congruent with previous findings, providing explicit instructions resulted in a significant decrease in response times to sequenced stimuli during acquisition. Individuals who physically performed the sequences during practice exhibited performance during direct and indirect tests consistent with parallel activation of both the explicit and implicit systems. Unexpectedly, performance on the indirect test for the observers that revealed explicit learning was similar to that reported for the model, indicating parallel activation also occurred during observation. This finding addresses some of the predictions made by Willingham’s COBALT (1998). Furthermore, a subset of observers revealed no explicit knowledge of the 12-element sequence but performed well on the indirect test. Learning via the implicit system during observation is congruent with recent behavioral data of Bird and colleagues (2005).

The following two studies examined the influence of spatial regularities on our ability to learn and predict frequencies and sequences of events. Research into statistical and sequence learning has demonstrated that we can learn the statistical properties of events and use this knowledge to make predictions about future events. Research has also demonstrated that redundant spatial features associated with events can influence our ability to respond to and discriminate between different stimuli. The goal of this thesis was to test whether redundant spatial features could influence our ability to notice non-spatial regularities in an environment. Using a computerized version of the children’s game ‘rock-paper-scissors’ (RPS), undergraduates were instructed to win as often as possible against a computer that played varying strategies. For each strategy, the computer’s plays were either presented with spatial regularity (i.e., ‘rock’ would always appear on the left of the screen, ‘paper’ in the middle, and ‘scissors’ on the right) or without spatial regularity (i.e., the items were equally likely to appear in any of the three screen locations). The results showed that, although irrelevant to the task itself, spatial regularities had a moderate influence when participants learned to exploit easy strategies, and a more pronounced influence when learning to exploit harder strategies. This research suggests that redundant spatial features can influence our ability to learn and represent distributions of events.

It has been suggested that improvement in the performance of many motor sequence tasks such as playing musical instruments, operating complex machinery or tools, and/or performing a variety of athletic activities results from the learner’s ability to parse the movement into fundamental action primitives called motor chunks. Moreover, it has been suggested that the organization of motor chunks within a sequential behavior can be influenced by consolidation occurring outside the boundary of practice during which reorganization can occur leading to faster sequence production. The present study involved modest practice of a discrete sequence production task (DSPT) followed by subsequent assessment of performance of this task either immediately after the completion of practice or after a 24-hr delay. Of critical interest was the change in performance from the end of training to the test phase in three features of the sequence implementation namely sequence initiation, motor chunk transition, and element execution components. It was anticipated that motor chunk transition would be susceptible to significantly greater offline enhancement in the 24-hr delayed test case. Based on the extant literature it was also expected that sequence initiation and/or execution processes may also be sensitive to offline consolidation. No evidence emerged that supported the proposal that motor chunk transitions revealed additional gains following a longer interval between training and test. It is possible this effect was underestimated because of some imprecision in the manner in which motor chunk transitions were identified. There was clear evidence for offline gains for both sequence initiation and element execution processes. These data are difficult to interpret within the framework of a number of contemporary accounts of sequence production such as the dual-processor model in which sequence production is governed by a cognitive and motor processor.

The following two studies examined the influence of spatial regularities on our ability to learn and predict frequencies and sequences of events. Research into statistical and sequence learning has demonstrated that we can learn the statistical properties of events and use this knowledge to make predictions about future events. Research has also demonstrated that redundant spatial features associated with events can influence our ability to respond to and discriminate between different stimuli. The goal of this thesis was to test whether redundant spatial features could influence our ability to notice non-spatial regularities in an environment. Using a computerized version of the children’s game ‘rock-paper-scissors’ (RPS), undergraduates were instructed to win as often as possible against a computer that played varying strategies. For each strategy, the computer’s plays were either presented with spatial regularity (i.e., ‘rock’ would always appear on the left of the screen, ‘paper’ in the middle, and ‘scissors’ on the right) or without spatial regularity (i.e., the items were equally likely to appear in any of the three screen locations). The results showed that, although irrelevant to the task itself, spatial regularities had a moderate influence when participants learned to exploit easy strategies, and a more pronounced influence when learning to exploit harder strategies. This research suggests that redundant spatial features can influence our ability to learn and represent distributions of events.

Fluent speech production requires rapid coordination among respiratory, laryngeal, and articulatory processes and is mediated by multiple neural systems (Bohland & Guenther, 2006). Stuttering is a fluency disorder characterized by core deficits in speech motor planning. Previous research indicates people who stutter (PWS) exhibit deficits in speech motor sequence learning and are slower and less accurate over practice relative to fluent speakers (Ludlow, Siren, & Zikira, 2004; Namasivayam & VanLieshout, 2004; Smits-Bandstra & De Nil, 2007; Smits-Bandstra, De Nil, & Saint-Cyr, 2006). Furthermore, the neural bases of impaired speech motor sequence learning in PWS are not well understood. We present a study in which PWS (n=18) and persons with fluent speech (PFS) (n=17) were taught phonotactically illegal (e.g. gbesb) and phonotactically legal (e.g. blerk) speech motor sequences over two practice sessions. Functional magnetic resonance imaging (fMRI) was used to investigate brain regions underlying the production of learned illegal syllables and novel illegal syllables. With practice, subjects produced syllables more accurately, which is indicative of motor sequence learning. Our findings suggest a speech motor performance deficit in PWS. Furthermore, these findings indicate speech motor sequence learning relies on a speech motor sequence learning network.

No description available.

This thesis aims to investigate how well associative learning can account for human sequence learning under incidental conditions. It seems that we can learn complex sequential information about events in our environment, for example language or music, incidentally, without being aware of it. Awareness is, however, a complex issue with arguments for (Dienes, 2012) and against (Shanks, 2005) the existence of implicit learning processes. A dual process account proposes that there exist two different learning systems, one based on conscious, controlled reasoning and rules, and the other based on automatic association formation, which can take place outside of awareness (McLaren, Green, & Mackintosh, 1994). This thesis attempts to use the predictions of an associative account in conjunction with a suitable method for investigating implicit learning: sequence learning (Destrebecqz & Cleeremans, 2003). The research involves a collection of serial reaction time (SRT) tasks whereby participants respond to on-screen stimuli that follow a sequence that they were (intentional learning) or were not (incidental learning) informed of. Following on from the experimental design of Jones and McLaren (2009) this thesis provides evidence that humans differ in their ability to learn different sequential contingencies. After training sequences of trials where the current trial location was twice as likely to be either: the same as (Same rule); or different to (Different rule) the location two trials before this, participants were far better at learning the latter rule. I found that this result was not adequately simulated by the benchmark associative model of sequence learning, the Augmented SRN (Cleeremans & McClelland, 1991), and present a revised model. This model, amongst other attributes, represents all the stimuli experienced by participants and can therefore learn stimulus-response contingencies. These seem to block learning (to some extent) about the Same rule thus providing an associative explanation of the advantage for acquisition of the Different rule. Further predictions regarding the role of additional stimuli alongside sequence learning were then derived from this associative account and tested on human participants. The first of these was that additional stimuli within the task will interact with sequence learning. I found that human participants show increased Same rule learning when additional, concurrently presented stimuli follow the previous element in the sequence. I demonstrate that when participants perform an SRT task where responses are predicted by the colour of a cue, they are able to learn about this relationship in the absence of awareness. Using this cue-response learning I further investigate cue-competition between sequences and colours under incidental conditions and find evidence that suggests between cue associations may alter the influence of cue competition. These results altogether suggest that stimuli – both simple and sequential – can be learned under incidental conditions. This thesis further proposes that learning about simple and more complex relationships between stimuli interacts according to the predictions of an associative account and provides evidence that contributes to a dual process understanding of human learning.

The purpose of this thesis was to examine the capacity for acquisition and retention of practice-related improvements in compensatory posture control and the nature of postural motor learning among healthy young and older adults repeatedly exposed to continuous surface motion via a translating platform. Although much research has been conducted to examine the strategies adopted by the central nervous system to control posture in response to external perturbations, the learning capabilities of this system have remained relatively unexplored. Many of the studies that have explored practice-related changes in balance performance have focused on short-term adaptations to highly predictable stimuli. Borrowing from implicit sequence learning paradigms, we developed two experimental protocols to examine postural motor learning for a compensatory balance task in an environment with limited predictability. Applying key principles of motor learning to our experimental design including retention intervals and a transfer task enabled us to draw conclusions about the permanency and specificity of the observed changes. Our investigations revealed practice-related changes in the motor organization of posture control. In young adults, a shift in the complexity of the control strategy occurred which lead to improvements in spatial and temporal control of the COM. In contrast, a majority of older adults persisted with a simplified control strategy which restricted improvements in COM control. Importantly, despite control strategy differences, the two groups showed comparable rates of improvement in almost all outcome measures including measures of trunk stability and temporal COM control. Longer-term retention of behavioural changes provided evidence for learning in young adults. Similar maintenance of improvements was observed for some outcome measures in older adults. Where significant losses in performance occurred in this group, retention was evident in the rapid reacquisition of performance to the level of proficiency achieved in original practice. Based on these results, we concluded that age affected the adapted control strategy but not the capacity for postural motor learning. Further, regardless of age or protocol, the pattern of postural perturbations did not influence acquisition of a strategy of stability and thus, we concluded that postural motor learning under the current conditions was non-specific, that is, it did not involve sequence-specific learning. These results provide important insight into the generalized nature of compensatory postural motor learning and subsequently, into the potential for positive transfer of balance skill to other balance tasks.

The purpose of this thesis was to examine the capacity for acquisition and retention of practice-related improvements in compensatory posture control and the nature of postural motor learning among healthy young and older adults repeatedly exposed to continuous surface motion via a translating platform. Although much research has been conducted to examine the strategies adopted by the central nervous system to control posture in response to external perturbations, the learning capabilities of this system have remained relatively unexplored. Many of the studies that have explored practice-related changes in balance performance have focused on short-term adaptations to highly predictable stimuli. Borrowing from implicit sequence learning paradigms, we developed two experimental protocols to examine postural motor learning for a compensatory balance task in an environment with limited predictability. Applying key principles of motor learning to our experimental design including retention intervals and a transfer task enabled us to draw conclusions about the permanency and specificity of the observed changes. Our investigations revealed practice-related changes in the motor organization of posture control. In young adults, a shift in the complexity of the control strategy occurred which lead to improvements in spatial and temporal control of the COM. In contrast, a majority of older adults persisted with a simplified control strategy which restricted improvements in COM control. Importantly, despite control strategy differences, the two groups showed comparable rates of improvement in almost all outcome measures including measures of trunk stability and temporal COM control. Longer-term retention of behavioural changes provided evidence for learning in young adults. Similar maintenance of improvements was observed for some outcome measures in older adults. Where significant losses in performance occurred in this group, retention was evident in the rapid reacquisition of performance to the level of proficiency achieved in original practice. Based on these results, we concluded that age affected the adapted control strategy but not the capacity for postural motor learning. Further, regardless of age or protocol, the pattern of postural perturbations did not influence acquisition of a strategy of stability and thus, we concluded that postural motor learning under the current conditions was non-specific, that is, it did not involve sequence-specific learning. These results provide important insight into the generalized nature of compensatory postural motor learning and subsequently, into the potential for positive transfer of balance skill to other balance tasks.

Under typical between stimulus dual-task conditions, implicit sequence learning typically suffers, except under within stimulus conditions, where the stimuli for both tasks are the same. This finding is inconclusive, given that it has not been replicated and the study under which it was obtained was methodologically flawed. The finding also seemed to contradict the psychological refractory period finding that simultaneous presentation of the two task stimuli will result in performance decrements. Two experiments were conducted to test the effect of within stimulus presentation in a dual-task implicit learning task. In Experiment 1, within stimulus presentation resulted in improved sequence learning, relative to between stimulus presentation. The second experiment did not show an effect of response selection load under within stimulus presentation conditions. The findings suggest that implicit learning can occur under attentionally demanding conditions, but that the incidental task structure to be learned should be comprised of stimuli that are already attended during primary task processing.