Weaver mutant mice exhibit long-term learning deficits under several measures of instrumental behavior.

Homozygous weaver mutant mice (wv/wv) exhibit symptoms that parallel Parkinson's disease, including motor deficits and the destruction of dopaminergic neurons as well as degeneration in the cerebellum and hippocampus. To develop a more complete behavioral profile of these organisms, groups of wv/wv, wv/+ mice and C57BL/6 mice were observed on a within-subjects basis under a fixed-interval schedule of reinforcement, a differential-reinforcement-of-low-rate-of-responding schedule, and a discrimination task in which a saccharin solution and tap water were concurrently available from two food cups. Under both reinforcement schedules, the wv/wv mice responded as frequently as the comparison subjects, but they responded in a manner that was inappropriate to the contingencies. Rather than respond with increasing frequency as the upcoming reinforcer became temporally proximate, wv/wv mice responded with decreasing probability as a function of the time since the previous reinforcer. Under the discrimination task, the wv/wv mice, unlike the controls, obtained saccharin over tap water at the level of chance. The findings suggest that weaver mutant mice express learning deficits similar to those found in other dopamine-deficient organisms.

A multilevel approach to relating subjective workload to performance after shifts in task demand.

OBJECTIVE: The aim of this laboratory experiment was to demonstrate how taking a longitudinal, multilevel approach can be used to examine the dynamic relationship between subjective workload and performance over a given period of activity involving shifts in task demand. BACKGROUND: Subjective workload and conditions of the performance environment are oftentimes examined via cross-sectional designs without distinguishing within-from between-person effects. Given the dynamic nature of performance phenomena, multilevel designs coupled with manipulations of task demand shifts are needed to better model the dynamic relationships between state and trait components of subjective workload and performance. METHOD: With a sample of 75 college students and a computer game representing a complex decision-making environment, increases and decreases in task demand were counterbalanced and subjective workload and performance were measured concurrently in regular intervals within performance episodes. Data were analyzed using hierarchical linear modeling. RESULTS: Both between- and especially within-person effects were dynamic. Nevertheless, at both levels of analysis, higher subjective workload reflected performance problems, especially more downstream from increases in task demand. CONCLUSION: As a function of cognitive-energetic processes, shifts in task demand are associated with changes in how subjective workload is related to performance over a given period of activity. Multilevel, longitudinal approaches are useful for distinguishing and examining the dynamic relationships between state and trait components of subjective workload and performance. APPLICATION: The findings of this research help to improve the understanding of how a sequence of demands can exceed a performer's capability to respond to further demands.

Learner-controlled practice difficulty in the training of a complex task: cognitive and motivational mechanisms.

An inherent aspect of learner-controlled instructional environments is the ability of learners to affect the degree of difficulty faced during training. However, research has yet to examine how learner-controlled practice difficulty affects learning. Based on the notion of desirable difficulties (Bjork, 1994), this study examined the cognitive and motivational antecedents and outcomes of learner-controlled practice difficulty in relation to learning a complex task. Using a complex videogame involving both strong cognitive and psychomotor demands, 112 young adult males were given control over their practice difficulty, which was reflected in the complexity of the training task. Results show that general mental ability, prior experience, pre-training self-efficacy, and error encouragement were positively related to learner-controlled practice difficulty. In turn, practice difficulty was directly related to task knowledge and post-training performance, and it was related to adaptive performance through the mediating influences of task knowledge and post-training performance. In general, this study supports the notion that training difficulty operationalized in terms of task complexity is positively related to both knowledge and performance outcomes. Results are discussed with respect to the need for more research examining how task complexity and other forms of difficulty could be leveraged to advance learner-controlled instructional practices.