Likelihood of attending to the color word modulates Stroop interference

Three experiments investigated whether the Stroop color-naming effect is modulated by the likelihood of a color word capturing visual attention. In Experiment 1, a bar or a neutral word was presented at fixation as a color carrier, along with a color word randomly appearing in either an achromatic color (white in the main experiment, gray in a follow-up) or purple. Reduction of the Stroop effect (known as Stroop dilution) occurred when the color word was achromatic but not (or to a lesser extent) when it was in purple. In Experiment 2, the color of the color word remained constant throughout trial blocks, and Stroop dilution was equally evident when the word was always in purple and when it was always in white. In Experiment 3, a color bar was presented as the color carrier with both a color word and a neutral word. In this case, the Stroop effect was larger when the color word appeared in purple, and smaller when the neutral word appeared in purple, than when neither word did. These results imply that the extent to which processing of a color word occurs is determined by the likelihood of the word capturing attention.     

The Simon task with multi-component responses: two loci of response–effect compatibility

The stimulus–response compatibility (SRC) effect refers to the phenomenon that responses are faster and more accurate when stimulus and response correspond than when they do not. The phenomenon is robust in that it is observed even when SRC is irrelevant to performing the task, a variant known as the Simon effect. Recent studies also demonstrated that responses are faster when they are spatially compatible with their effects in the environment (action effects) than when they are incompatible. This response–effect (R–E) compatibility effect is thought to stem from the fact that stimuli first activate anticipated effect codes, which then activate corresponding action codes. In the present study, the Simon task was used to examine influences of multiple response components on performance. Three response components were orthogonally manipulated. The results of three experiments indicated that there are two separate processes that are influenced by R–E compatibility; one that is responsible for the SRC effect (S–R translation) and the other that is independent of SRC (action programming). The influence of R–E compatibility on the former process depended on manipulations that varied attentional demands of the task.     

Influence of temporal overlap on time course of the Simon effect

Two experiments are reported in which we manipulated relevant and irrelevant stimulus dimensions to assess whether an increase in temporal overlap would influence the time course of a "standard" Simon effect (obtained when visual stimuli are presented on the left/right of the screen and left/right responses are performed with uncrossed hands). This procedure is new in two ways: First, the manipulations were intended to reduce, instead of increase, the distance between conditional and unconditional response-activation processes. Second, we manipulated the relevant and irrelevant stimulus dimensions in a manner that did not vary stimulus onset asynchronies, precues, or go/no go trials, or alter the stimulus quality. Results were consistent with the hypothesis that when the two response processes are shifted closer to each other, the Simon effect would be sustained across time, instead of decreasing as typically found. These findings are discussed in line with the temporal overlap hypothesis and with an automatic activation account.     

Influences of response position and hand posture on the orthogonal Simon effect

When lateralized responses are made to the locations of vertically arrayed stimuli, two types of mapping effect have been reported: an overall up-right/down-left advantage and mapping preferences that vary with response position. According to Cho and Proctor's (2003) multiple asymmetric codes account, these orthogonal stimulus-response compatibility effects are due to the correspondence of stimulus polarity and response polarity, as determined by the positions relative to multiple frames of reference. The present study examined these two types of orthogonal compatibility for situations in which participants made left-right responses to the colours of a vertically arrayed stimulus set, and stimulus location was irrelevant. Although a significant orthogonal Simon effect was not evident when responding at a centred, neutral response position, the effect was modulated by response eccentricity (Experiment 2) and hand posture (Experiment 3). These effects are qualitatively similar to those obtained when stimulus location is task relevant. The results imply that, as Proctor and Cho's (2006) polarity correspondence principle suggests, the stimulus polarity code activates the response code of corresponding polarity even when stimulus location is irrelevant to the task.     

Are spatial responses to visuospatial stimuli and spoken responses to auditory letters ideomotor-compatible tasks? Examination of set-size effects on dual-task interference

Previous studies have paired a visual-manual Task 1 with an auditory-vocal Task 2 to evaluate whether the psychological refractory period (PRP) effect is eliminated with two ideomotor-compatible tasks (for which stimuli resemble the response feedback). The present study varied the number of stimulus-response alternatives for Task 1 in three experiments to determine whether set-size and PRP effects were absent, as would be expected if the tasks bypass limited-capacity response-selection processes. In Experiments 1 and 2, the visual-manual task was used as Task 1, with lever-movement and keypress responses, respectively. In Experiment 3, the auditory-vocal task was used as Task 1 and the visual-manual task as Task 2. A significant lengthening of reaction time for 4 vs. 2 alternatives was found for the visual-manual Task 1 and the Task 2 PRP effect in Experiments 1 and 2, suggesting that the visual-manual task is not ideomotor compatible. Neither effect of set size was significant for the auditory-vocal Task 1 in Experiment 3, but there was still a Task 2 PRP effect. Our results imply that neither version of the visual-manual task is ideomotor compatible; other considerations suggest that the auditory-vocal task may also still require response selection.     

Validation of scales from the Deployment Risk and Resilience Inventory in a sample of Operation Iraqi Freedom veterans

The Deployment Risk and Resilience Inventory (DRRI) is a suite of scales that can be used to assess deployment-related factors implicated in the health and well-being of military veterans. Although initial evidence for the reliability and validity of DRRI scales based on Gulf War veteran samples is encouraging, evidence with respect to a more contemporary cohort of Operation Iraqi Freedom (OIF) veterans is not available. Therefore, the primary goal of the present study was to validate scales from the DRRI in a large sample of OIF army personnel diversified in occupational and demographic characteristics. In general, results supported the use of these DRRI scales in this population. Internal consistency reliability estimates were quite strong. Additionally, support was obtained for criterion-related validity, as demonstrated by associations with mental and physical health measures, and discriminative validity, as demonstrated by differences between key military subgroups.     

Is the psychological refractory period effect for ideomotor compatible tasks eliminated by speed-stress instructions?

It has been argued that the psychological refractory period (PRP) effect is eliminated with two ideomotor compatible tasks when instructions stress fast and simultaneous responding. Three experiments were conducted to test this hypothesis. In all experiments, Task 1 required spatially compatible manual responses (left or right) to the direction of an arrow, and Task 2 required saying the name of the auditory letter A or B. In Experiments 1 and 3, the manual responses were keypresses made with the left and right hands, whereas in Experiment 2 they were left-right toggle-switch movements made with the dominant hand. Instructions that stressed response speed reduced reaction time and increased error rate compared to standard instructions to respond fast and accurately, but did not eliminate the PRP effect on Task 2 reaction time. These results imply that, even when response speed is emphasized, ideomotor compatible tasks do not bypass response selection.     

The effect of causal knowledge on judgments of the likelihood of unknown features

People frequently infer unknown aspects of an entity based on their knowledge about that entity. The current study reports a novel phenomenon, an inductive bias people have in making such inferences. Upon learning that one symptom causes another in a person, both undergraduate students (Experiment 1) and clinicians (Experiment 2) judged that an unknown feature associated with the cause-symptom was more likely to be present in that person than an unknown feature associated with the effect-symptom. Thus, these findings suggest a specific mechanism in which causal explanations influence one’s representation of and inferences about an entity. Implications for clinical reasoning and associative models of conceptual knowledge are discussed.     

Transfer of orthogonal stimulus-response mappings to an orthogonal Simon task

When up-down stimulus locations are mapped to left-right keypresses, an overall advantage for the up-right/down-left mapping is often obtained that varies as a function of response eccentricity. This orthogonal stimulus-response compatibility (SRC) effect also occurs when stimulus location is irrelevant, a phenomenon called the orthogonal Simon effect, and has been attributed to correspondence of stimulus and response code polarities. The Simon effect for horizontal stimulus-response (S-R) arrangements has been shown to be affected by short-term S-R associations established through the mapping used for a prior SRC task in which stimulus location was relevant. We examined whether such associations also transfer between orthogonal SRC and Simon tasks and whether correspondence of code polarities continues to contribute to performance in the Simon task. In Experiment 1, the orthogonal Simon effect was larger after practising with an up-right/down-left mapping of visual stimuli to responses than with the alternative mapping, for which the orthogonal Simon effect tended to reverse. Experiment 2 showed similar results when practice was with high (up) and low (down) pitch tones, though the influence of practice mapping was not as large as that in Experiment 1, implying that the short-term S-R associations acquired in practice are at least in part not modality specific. In Experiment 3, response eccentricity and practice mapping were shown to have separate influences on the orthogonal Simon effect, as expected if both code polarity and acquired S-R associations contribute to performance.     

Reducing and restoring stimulus-response compatibility effects by decreasing the discriminability of location words

In two experiments, we compared level of activation and temporal overlap accounts of compatibility effects in the Simon task by reducing the discriminability of spatial and non-spatial features of a target location word. Participants made keypress responses to the non-spatial or spatial feature of centrally presented location words. The discriminability of the spatial feature of the word (Experiment 1), or of both the spatial and non-spatial feature (Experiment 2), was manipulated. When the spatial feature of the word was task-irrelevant, lowering the discriminability of this feature reduced the compatibility effect. The compatibility effect was restored when the discriminability of both the task-relevant and task-irrelevant features were reduced together. Results provide further evidence for the temporal overlap account of compatibility effects. Furthermore, compatibility effects when the spatial information was task-relevant and those when the spatial information was task-irrelevant were moderately correlated with each other, suggesting a common underlying mechanism in both versions.