Ideomotor compatibility in the psychological refractory period effect: 29 years of oversimplification

Four experiments examined whether the psychological refractory period (PRP) effect can be eliminated with ideomotor compatible (IM) but not stimulus-response compatible (SR) tasks, as reported by A. G. Greenwald and H. G. Shulman (1973). Their tasks were used: a left or right movement to a left- or right-pointing arrow (IM) or to the word left or right (SR) for Task 1; saying "A" or "B" (IM) or "1" or "2" (SR) to an auditory A or B for Task 2. The stimulus onset asynchronies were 0, 100, 200, 300, 500, and 1,000 ms in Experiment 1, and only 0, 100, 200, and 1,000 ms in Experiments 2-4. The arrow was in the center of the screen in Experiments 1-3 and to the left or right in Experiment 4. As in Greenwald and Shulman's Experiment 2, the instructions stated that most often the 2 stimuli would be presented simultaneously. A PRP effect was obtained in all conditions, most likely because response-selection decisions are required even for IM tasks.     

Auditory stimulus-response compatibility: Is there a contribution of stimulus-hand correspondence?

 Simon, Hinrichs, and Craft found that when subjects responded to a tone in the left or right ear with a left or right keypress, both ear-response-location correspondence and ear-hand correspondence affected reaction time. This outcome is in contrast to results obtained for auditory and visual Simon tasks (i.e., tasks in which stimulus location is irrelevant) as well as results obtained in visual stimulus-response (S-R) compatibility studies, which show only an effect of spatial S-R correspondence. Experiment 1 was a replication of Simon et al.'s experiment in which spatial mapping and hand placement (uncrossed, crossed) were varied. The results were inconsistent with those of Simon et al., showing no ear-hand compatibility effect. Experiment 2 was a second replication with an additional condition examined in which the stimuli were visual locations. The results showed no contribution of stimulus-hand correspondence for either auditory or visual stimuli. Experiment 3 was a replication of another experiment by Simon et al. in which tone pitch was relevant and tone location irrelevant. Like Simon et al.'s data, our results showed no indication that stimulus-hand correspondence is a significant factor. Overall, our results imply that regardless of whether tone location is relevant or irrelevant, ear-response-location correspondence is the only factor that contributes to S-R compatibility in auditory two-choice reaction tasks. Received: 15 March 1999 / Accepted: 8 June 1999     

Still no evidence for perfect timesharing with two ideomotor-compatible tasks: a reply to Greenwald (2003)

For 30 years, A. G. Greenwald and H. G. Shulman's (1973) psychological refractory period (PRP) study has been cited as evidence for perfect timesharing with ideomotor (IM)-compatible tasks. Recently, M.-C. Lien, R. W. Proctor, and P. A. Allen (2002) failed to replicate these results and concluded that IM compatibility is neither necessary nor sufficient to eliminate the PRP effect. A. G. Greenwald (2003) attributed Lien et al.'s nonreplication to the use of (a) a non-IM-compatible task, (b) varied trial spacing, and/or (c) inappropriate instructions. The authors of the present article argue that the first 2 factors are not critical and that instructions merely affect the criterion for speed versus accuracy. In each of Greenwald's experiments, dual-task costs were evident on response time or error rates. Furthermore, the small dual-task costs in his study are consistent with a bottleneck model. Thus, Greenwald (2003) does not provide evidence that IM-compatible tasks enable perfect timesharing.     

Task switching and response correspondence in the psychological refractory period paradigm

Three experiments examined the effects of task switching and response correspondence in a psychological refractory period paradigm. A letter task (vowel-consonant) and a digit task (odd-even) were combined to form 4 possible dual-task pairs in each trial: letter-letter, letter-digit, digit-digit, and digit-letter. Foreknowledge of task transition (repeat or switch) and task identity (letter or digit) was varied across experiments: no foreknowledge in Experiment 1, partial foreknowledge (task transition only) in Experiment 2, and full foreknowledge in Experiment 3. For all experiments, the switch cost for Task 2 was additive with stimulus onset asynchrony, and the response-correspondence effect for Task 2 was numerically smaller in the switch condition than in the repeat condition. These outcomes suggest that reconfiguration for Task 2 takes place after the central processing of Task 1 and that the crosstalk correspondence effect is due to response activation by way of stimulus-response associations.     

Flowers and spiders in spatial stimulus-response compatibility: does affective valence influence selection of task-sets or selection of responses?

The present study examined the effect of stimulus valence on two levels of selection in the cognitive system, selection of a task-set and selection of a response. In the first experiment, participants performed a spatial compatibility task (pressing left and right keys according to the locations of stimuli) in which stimulus-response mappings were determined by stimulus valence. There was a standard spatial stimulus-response compatibility (SRC) effect for positive stimuli (flowers) and a reversed SRC effect for negative stimuli (spiders), but the same data could be interpreted as showing faster responses when positive and negative stimuli were assigned to compatible and incompatible mappings, respectively, than when the assignment was opposite. Experiment 2 disentangled these interpretations, showing that valence did not influence a spatial SRC effect (Simon effect) when task-set retrieval was unnecessary. Experiments 3 and 4 replaced keypress responses with joystick deflections that afforded approach/avoidance action coding. Stimulus valence modulated the Simon effect (but did not reverse it) when the valence was task-relevant (Experiment 3) as well as when it was task-irrelevant (Experiment 4). Therefore, stimulus valence influences task-set selection and response selection, but the influence on the latter is limited to conditions where responses afford approach/avoidance action coding.     

Associations of Stress Exposures and Social Support With Long-Term Mental Health Outcomes Among U.S. Iraq War Veterans

The long-term mental health effects of war-zone deployment in the Iraq and Afghanistan wars on military personnel are a significant public health concern. Using data collected prospectively at three distinct assessments during 2003–2014 as part of the Neurocognition Deployment Health Study and VA Cooperative Studies Program Study #566, we explored how stress exposures prior, during, and after return from deployment influence the long-term mental health outcomes of posttraumatic stress disorder (PTSD), depression, anxiety disorders, and problem drinking. Longer-term mental health outcomes were assessed in 375 service members and military veterans an average of 7.5 years (standard deviation = 1.0 year) after the initial (i.e., “index”) Iraq deployment following their predeployment assessment. Anxiety disorder was the most commonly observed long-term mental health outcome (36.0%), followed by depression (24.5%), PTSD (24.3%), and problem drinking (21.0%). Multivariable regression models showed that greater postdeployment stressors, as measured by the Post-Deployment Life Events scale, were associated with greater risk of depression, anxiety disorders, and problem drinking. Anxiety disorder was the only outcome affected by predeployment stress concerns. In addition, greater postdeployment social support was associated with lower risk of all outcomes except problem drinking. These findings highlight the importance of assessing postdeployment stress exposures, such as stressful or traumatic life events, given the potential impact of these stressors on long-term mental health outcomes. This study also highlights the importance of postdeployment social support as a modifiable protective factor that can be used to help mitigate risk of long-term adverse mental health outcomes following war-zone exposure.     

Determinants of the benefit for consistent spatial mappings in dual-task performance of three-choice tasks

Performance of pairs of three-choice tasks shows a consistency benefit for which reaction times are shorter when the stimulus-response mappings for each task are consistent (both corresponding or both mirrored) than when they are inconsistent. In the present study, we examined whether this consistency benefit is reduced at long stimulus onset asynchronies, as it is for pairs of two-choice tasks, or is relatively unaffected, as it is for pairs of four-choice tasks. The consistency benefit was evident for both corresponding and mirrored mappings, at all intervals. For consistent mirrored mappings, the benefit was found for the side stimulus positions (for which responses are crossed) but not for the center position, whereas for consistent corresponding mappings, a benefit was evident for the center position as well. The results for both mappings are in agreement with an emergent mapping-choice account. The consistent corresponding mapping also benefits from subjects’ ability to apply a respond-corresponding rule across tasks. An emergent perceptual-feature process that contributes to the consistency benefit for two-choice tasks does not seem to play a role in tasks with three or more choices.     

Persistence of stimulus-response compatibility effects with extended practice.

The influence of extended practice on stimulus-response (S-R) compatibility effects was investigated. Three experiments, each extending over a period of 8 sessions, were conducted. The nature and degree of compatibility was manipulated across experiments. In all experiments, a persistent effect of S-R compatibility on reaction times was observed. Thus, the lower bound for reaction times appears to be less for compatible assignments than for incompatible assignments. This persistence of S-R compatibility indicates that the initial codings used to perform a novel task continue to exert an influence on later performance.