Recent controversy surrounds the use of the Trail Making Test as a measure of cognitive flexibility, given that the Trail Making Test, Part B (TMT-B) also differs from Part A (TMT-A) in factors of motor control and perceptual complexity. The present study compared performance in the TMT and a set-switching task in order to test the assumption that cognitive flexibility is captured in TMT-B performance. Set-switching tasks have low motor and perceptual selection demands, and therefore provide a clearer index of executive function. In this study, participants made category judgments for digits, letters, or symbols across a series of trials, and performance for consecutive same-task trials was compared with task-switch trials. Results of the set-switching task indicated significant switch cost, but only for the situation of task alternation (e.g., an ABA series), suggesting that task-set inhibition may play a role in this effect. Alternating-switch cost was significantly correlated with TMT-B performance, es...

Executive processes necessary for flexibly switching between different tasks were studied using a set switching paradigm that requires participants to rapidly switch between different tasks across consecutive trials. Switch cost reflects poorer performance for task-switch trials than for consecutive same-task trials. Significant switch cost was observed even with considerable preparation time before a task-switch, an effect known as residual switch cost. This study tested the hypothesis that one process underlying residual switch cost is inhibition of the previous task-set. We used semantic categorization tasks to compare switch cost between alternating task series (ABA) and nonalternating series (ABC) in order to test the generality of a task-set inhibition effect previously observed with perceptual judgment tasks (Mayr & Keele, in press). The results yielded significant switch cost only for alternating tasks, in both response times and errors resulting from performance of the wrong task. Thus, resolving inhibition associated with previously abandoned task-sets may be the main process underlying residual switch costs, suggesting that task-set inhibition is an important executive control process.

There is robust evidence that contact with the natural world improves human health, including emotional well-being. However, the specific conditions of emotional benefits of nature contact are sparsely understood. Two studies were conducted with university students to examine whether the duration of nature contact influences the magnitude of benefits for both hedonic (positive and negative affect) and self-transcendent emotions. Study 1 investigated whether 5 minutes of sedentary nature contact influenced both emotion types, and Study 2 examined whether mood improvements are sensitive to the duration of nature contact (5 vs. 15 minutes). Results indicate that brief nature contact reliably improved both hedonic and self-transcendent emotions, and that the duration of contact in the range tested had no impact on this improvement.

Task-switching performance is strongly influenced by whether the imperative stimulus uniquely specifies which task to perform: Switch cost is substantial with bivalent stimuli but is greatly reduced with univalent stimuli, suggesting that available contextual information influences processing in task-switching situations. The present study examined whether task-relevant information provided by task cues influences the magnitude of switch cost in a parallel manner. Cues presented 500 ms prior to a trivalent stimulus indicated which of three tasks to perform. These cues either had a preexisting association with the to-be-performed task (verbal cues), or a recently learned association with the task (spatial and shape cues). The results paralleled the effects of stimulus bivalence: substantial switch cost with recently learned cue-task associations and greatly reduced switch cost with preexisting cue-task associations. This suggests that both stimulus-based and cue-based information can activate the relevant task set, possibly providing external support to endogenous control processes. Alternating-switch cost, a greater cost for switching back to a recently abandoned task, was also observed with both preexisting and recently learned cue-task associations, but only when all tasks were presented in a consistent spatial location. When spatial location was used to cue the to-be-performed tasks, no alternating-switch cost was observed, suggesting that different processes may be involved when tasks are uniquely located in space. Specification of the nature of these processes may prove to be complex, as post-hoc inspection of the data suggested that for the spatial cue condition, the alternating-switch cost may oscillate between cost and benefit, depending on the relevant task.

Asymmetric switch cost, observed when switching between tasks varying in difficulty, shows that the difference between repeat and switch trials is greater when switching to the easier task. Early explanations of this effect attributed this pattern to both positive priming of the difficult task and negative priming of the easier task, but more recent models have focused only on activation processes. The role of inhibition in asymmetric switch cost was examined using backward inhibition, a more direct measure of task-set inhibition. The results indicated asymmetric backward inhibition, with greater sequential inhibition of the easier task (i.e., easy-difficult-easy sequences). Switch costs, however, showed both typical and reversed asymmetry (greater cost when switching from the easy to the difficult task), depending on the relative difficulty of task pairs. This pattern of results indicates that switch costs are attributable to both activation and inhibition processes.