Control-display alignment determines the prevalent compatibility effect in two-dimensional stimulus-response tasks.

Responses are faster and more accurate when they are spatially compatible with a stimulus than when they are incompatible (the stimulus-response compatibility (SRC) effect). In studies using two-dimensional (2-D) stimulus and response sets in which stimuli and responses have both vertical (top-bottom) and horizontal (right-left) spatial relations, SRC effects are generally larger along the horizontal dimension, an effect called right-left prevalence. Several accounts have been posited to explain this asymmetry, including frames of reference to the body and spatio-anatomical constraints. We propose a new account of the right-left prevalence effect in which prevalence effects are largely determined by the spatial alignment between elements on the stimulus display and response locations on the control panel--the control-display alignment (CDA). For example, when responses are aligned below a display, 2-D stimulus and response sets share a common vertical midline that emphasizes a right-left distinction. When responses are to the right or left of the display, the shared midline is horizontal, emphasizing the top-bottom distinction and should instead lead to top-bottom prevalence effects. Participants completed two-choice, 2-D SRC tasks in four control-display configurations with a response panel centered above, below, left, and right of a projected display. As hypothesized, right-left prevalence was elicited using vertical CDA and top-bottom prevalence was elicited using horizontal CDA. The findings demonstrate that CDA largely determines prevalence effects and should be taken into account when using multidimensional stimulus and response sets.

Attention is captured by distractors that uniquely correspond to controlled objects: an analysis of movement trajectories.

When reaching for a particular target, movements tend to deviate toward distractors. Previously, we have shown that cursor movements deviate to a greater degree toward distractors when the distractor color corresponds to that of the cursor and the target color does not, even when this relationship is task-irrelevant (Miles & Proctor, 2011). In the present study, we investigated whether this correspondence effect is due to attention capture or to the activation of responses based on the task response rules associated with the colors of the distractor and target (viz. a flanker effect). Participants moved a central rectangular cursor to an upper left or upper right location, depending on the cursor color. The colors of the target (correct response side) and distractor (incorrect response side) were independent from one another and were either corresponding or noncorresponding with respect to the cursor color. In Experiment 1, reaction times were delayed when the distractor color corresponded to that of the cursor, but only when the target color did not correspond to the cursor color. No color correspondence effect was found for movement trajectories or movement times. However, in Experiment 2, when responses were time-pressured, initial movements toward the distractor were much more common when the distractor color exclusively corresponded to the cursor color. On the basis of these results, we argue that attention capture best explains the increased tendency to move a controlled object to a distractor that uniquely shares its features.

Correlations between spatial compatibility effects: are arrows more like locations or words?

Responses are more efficient when their spatial mappings with features of targets are compatible compared to when they are incompatible, even when those features are irrelevant to task performance. Currently, a debate exists as to whether spatial information conveyed by different stimulus modes leads to qualitatively different spatial representations. We investigated the relations between three of the most commonly used spatial stimulus modes-arrows, locations, and location words-using correlations of compatibility effects between each of these modes as well as compatibility effects at different segments of their response time distributions. Our results show that when spatial information is irrelevant to task performance (the Simon task), the compatibility effects elicited by arrows and words are more strongly related with each other than with those of locations. However, when spatial information is task relevant (the stimulus-response compatibility SRC task), the compatibility effects elicited by arrows and locations are more related, and both are less related to the effect elicited by words. We suggest that these changing relations between stimulus modes are strategically determined based on which spatial coding technique for arrows is most advantageous to task performance. Furthermore, the varying relations between these spatial compatibility effects indicate that the compatibility effect with one stimulus mode is not always predictive of the compatibility effect in another mode.

Colour correspondence effects between controlled objects and targets.

It is increasingly popular to use movement trajectories as a measure of mental processes related to task performance. Often this is accomplished by moving a cursor to a target on a computer screen. However, the relation between features of the cursor and the targets is rarely, if at all, considered. In five experiments, we examined whether moving a cursor to a target was affected by the relation between their colours, even when this relation was task irrelevant. In Experiments 1-3, a mouse-controlled cursor was moved to one of two coloured targets. Results showed colour correspondence effects in latency to initiate a response, duration of movement times, and movement trajectories when the relationship between cursor and target colours was task relevant (Experiment 1) and when only the cursor colour was task relevant (Experiment 2), but not when only the target was task relevant (Experiment 3). Follow-up experiments using single targets showed that colour correspondence effects occurred as long as attention was dedicated to the colour of the cursor, even when neither the cursor nor the target colour was relevant to selecting the correct movement (Experiments 4 and 5). Furthermore, when the relation between cursor and target colours is task irrelevant, colour correspondence effects for response initiation times are uncorrelated with those for movement times and movement trajectories. We interpret the observed correspondence effect in terms of response coding, although attention cueing may also play a role, and suggest that greater consideration of cursor features is needed when examining movement trajectories in choice reaction tasks.

Reaction time distribution analysis of spatial correspondence effects.

Since 1994, group reaction time (RT) distribution analyses of spatial correspondence effects have been used to evaluate the dynamics of the spatial Simon effect, a benefit of correspondence of stimulus location information with response location for tasks in which stimulus location is irrelevant. We review the history and justification for analyzing group RT distributions and clarify which conditions result in the Simon effect decreasing across the distribution and which lead to flat or increasing functions. Although the standard left-right Simon effect typically yields a function for which the effect decreases as RT increases, in most other task variations, the Simon effect remains stable or increases across the RT distribution. Studies that have used other means of evaluating the temporal dynamics of the Simon effect provide converging evidence that the changes in the Simon effect across the distribution are due mainly to temporal activation properties, an issue that has been a matter of some dispute.

Attention is required for acquisition but not expression of new response biases.

Throughout a lifetime of interaction with the physical environment, people develop a strong bias to respond on the same side as the location of a target object, even when its location is irrelevant to the task at hand. Recent research has shown that this compatibility bias can be overridden with relatively brief but focused training. To better understand how such training affects preexisting response biases, we investigated whether attention is required to acquire and express a new bias to respond on the opposite side, thus creating an incompatibility bias. Participants practiced making responses on the opposite side from left and right tones and then made responses based on the frequencies (high or low) of the same tones. As in previous research, practice with a spatially incompatible mapping eliminated the compatible bias in the Simon task. The addition of an attention load (continuous secondary tracking task) during practice prevented learning the new response bias. However, once the new bias was learned, it overrode the compatibility bias regardless of available attentional resources. We suggest that not only can a quickly learned response bias overwhelm preexisting biases that are acquired over years of experience but that recently learned and older, preexisting biases are similarly affected by attention load.

Action plans produce separate Simon effects for picking up and transporting objects.

A common type of interaction with the environment is reaching to move an object from one location to another. We investigated the influence of spatial stimulus-response (S-R) compatibility effects on the planning of such multi-reach actions. Participants responded to a cue on their left or right side by picking up a bean (initial reach) and then placing it in a container (goal reach). In three experiments, the initial reach and the goal reach were varied so that both reaches were to opposite sides (Exp 1), the initial reach was neutral (Exp 2), and both the initial and goal reaches were on the same side (Exp 3). The participants' reaction time to begin the initial reach was measured. Results showed that the spatial compatibility between the cue and both the initial and goal reaches contribute to the reaction time, with the relation between the cue and the initial reach playing a dominant role.

Dilution of compatibility effects in Simon-type tasks depends on categorical similarity between distractors and diluters.

The presence of a distracting stimulus during performance of the Stroop color-naming task leads to dilution of the Stroop effect. Because the automatic activation of word meaning may interfere with the task-relevant stimulus feature (text color; stimulus-stimulus [S-S] interference) and the response (saying the text color; stimulus-response [S-R] interference), it is unclear which of these types of interference is diluted. We introduce a new dilution paradigm using word- and arrow-based Simon tasks, in which only S-R interference is present. Participants made a left or right response to a central color target. A task-irrelevant location-word (Experiment 1) or arrow (Experiment 2) distractor adjacent to the target produced S-R compatibility effects. An additional neutral word or symbol series (diluter) was sometimes presented on the opposite side of the target from the distractor. The compatibility effect was smaller when the distractor and diluter category domains matched than when they mismatched. This result provides evidence that S-R compatibility effects are susceptible to the presence of diluters that are categorically similar to the distractors.

Non-intentional but not automatic: reduction of word- and arrow-based compatibility effects by sound distractors in the same categorical domain.

In the current study, we show that the non-intentional processing of visually presented words and symbols can be attenuated by sounds. Importantly, this attenuation is dependent on the similarity in categorical domain between the sounds and words or symbols. Participants performed a task in which left or right responses were made contingent on the color of a centrally presented target that was either a location word (LEFT or RIGHT) or a left or right arrow. Responses were faster when they were on the side congruent with the word or arrow. This bias was reduced for location words by a neutral spoken word and for arrows by a tone series, but not vice versa. We suggest that words and symbols are processed with minimal attentional requirements until they are categorized into specific knowledge domains, but then become sensitive to other information within the same domain regardless of the similarity between modalities.

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.

Improving performance through implementation intentions: are preexisting response biases replaced?

Commonly, the focus of a planned behavior is to attain some future goal. An alternative to this type of goal-focused, or goal-oriented, strategy is to emphasize the action required to meet the goal rather than to emphasize the goal itself. Previous research has suggested that an action-oriented plan, also known as an implementation-intention strategy, increases the chances of successfully reaching an intended future goal with minimal effort by making conscious, deliberate behaviors automatic. We investigated whether, within a Simon task, an implementation-intention strategy eliminates the contribution of preexisting response biases or whether it acts in addition to them. Results of two experiments show that an implementation-intention strategy provides a specific performance benefit that is in addition to, but not in place of, preexisting response biases.

Aging and time-sharing aspects of executive control.

A particularly important aspect of executive functioning involves the ability to coordinate two simultaneous activities. The role of this aspect of executive functioning in adult-age differences in cognitive performance was examined in a study involving 150 adults between 20 and 91 years of age who performed the same visual-motor tracking task with three different primary tasks. The participants also performed several additional cognitive tasks that allowed examination of the relation of time-sharing efficiency to other types of cognitive functioning The results were consistent with the existence of a distinct time-sharing ability because the time-sharing costs in the three dual-task combinations were significantly correlated with one another but only weakly correlated with other cognitive variables. Increased age was associated with reductions in time-sharing ability, and greater efficiency in performing two tasks at once was associated with better performance on tasks assessing spatial, reasoning, and memory abilities. Although this pattern is what one would expect if executive processes contribute to age differences in cognitive functioning, the effects were smaller than those associated with a perceptual speed construct.

The role of cognitive stimulation on the relations between age and cognitive functioning.

To make a convincing argument that cognitive stimulation moderates age trends in cognition there must be (a) a negative relation between age and level of cognitive stimulation, (b) a positive relation between level of cognitive stimulation and level of cognitive functioning, and (c) evidence of an interaction between age and cognitive stimulation in the prediction of cognitive functioning. These conditions were investigated in a study in which 204 adults between 20 and 91 years of age completed an activity inventory and performed a variety of cognitive tasks. Only the 1st condition received empirical support, and, thus, the results of this study provide little evidence for the hypothesis that cognitive stimulation preserves or enhances cognitive functioning that would otherwise decline.