Task switching with a 2:1 cue-to-task mapping: separating cue disambiguation from task-rule retrieval

An experiment is reported that investigated switching among two numerical judgment tasks with a factorial variation of the cue-to-task mapping (1:1 vs. 2:1) for each of the tasks. In addition, the precuing interval (CSI) was varied. The results suggest that with a long CSI of 1,100 ms, switching performance is almost completely determined by the task-specific conditional probability of a task switch given a cue switch. This effect probably reflects the complexity of task-rule retrieval. Without preparation (CSI = 0 ms), the complexity of cue disambiguation as a function of the number of cues across tasks seems to account for most part of the additional variance observed in this condition. The latter observation is in line with suggestions that increasing the number of cues per task from one to two introduces additional demands on the level of cue processing that reflect the transition from an isomorphic to a homomorphic mapping function.     

Priming cue encoding by manipulating transition frequency in explicitly cued task switching

Explicitly cued task switching with multiple cues per task permits three types of transitions: cue repetitions (cue and task repeat), task repetitions (cue changes but task repeats), and task alternations (cue and task change). The difference between task alternations and task repetitions can be interpreted as a switch cost, but its magnitude varies substantially across experiments. We investigated how switch cost is affected by transition frequency (how often subjects repeat and switch tasks) with an experiment in which each transition had a frequency of .70 in separate sessions. Switch cost was smallest when task alternations were frequent and largest when task repetitions were frequent. Mathematical modeling of the data indicated that the different “switch costs” reflected priming of cue encoding for frequent transitions. Interpretations of our findings based on automatic priming from memory retrieval of past transitions and strategic priming from transition expectancies are discussed.     

Task switching: on the origin of response congruency effects

When people frequently alternate between simple cognitive tasks, performance on stimuli which are assigned the same response in both tasks is typically faster and more accurate than on stimuli which require different responses for both tasks, thus indicating stimulus processing according to the stimulus-response (S-R) rules of the currently irrelevant task. It is currently under debate whether such response congruency effects are mediated by the activation of an abstract representation of the irrelevant task in working memory or by "direct" associations between specific stimuli and responses. We contrasted these views by manipulating concurrent memory load (Experiment 1) and the frequency of specific S-R associations (Experiment 2). While between-task response congruency effects were not affected by the amount of concurrent memory load, they were much stronger for stimuli that were processed frequently in the context of a competitor task. These findings are consistent with the idea that a large portion of the congruency effects stems from direct S-R associations and they do not support a sole mediation by task-set activation in working memory.     

Task switching: effects of practice on switch and mixing costs

In the task-switching paradigm, mixing costs indicate the performance costs to mix two different tasks, while switch costs indicate the performance costs to switch between two sequentially presented tasks. Applying tasks with bivalent stimuli and responses, many studies demonstrated substantial mixing and switch costs and a reduction of these costs as a result of practice. The present study investigates whether extensive practice of a task-switching situation including tasks with univalent stimuli eliminates these costs. Participants practiced switching between a visual and an auditory task. These tasks were chosen because they had shown eliminated performance costs in a comparable dual-task practice study (Schumacher et al. Psychol Sci 12:101–108, 2001). Participants either performed the tasks with univalent responses (i.e., visual-manual and auditory-verbal stimulus–response mappings) or bivalent responses (i.e., visual-manual and auditory-manual stimulus–response mappings). Both valence conditions revealed substantial mixing and switch costs at the beginning of practice, yet, mixing costs were largely eliminated after eight practice sessions while switch costs were still existent.     

Task rule-congruency and Simon-like effects in switching between spatial tasks

In task switching, a response indicated as correct by both task rules is executed more quickly than one for which the rules disagree. This rule-congruency, so far demonstrated unequivocally only in nonspatial tasks, shows that the currently irrelevant task set is kept active. However, in spatial task-switching, rule-congruency could potentially reflect a preexperimental tendency that contributes to a Simon-like effect. In the present study, participants switched between RIGHT-LEFT and UP-DOWN tasks with either a standard key arrangement (e.g., upper key = UP) or a mapping-reversed arrangement (e.g., up = DOWN), which reverses the direction of the potential Simon-like effect but leaves potential rule-congruency effects unchanged. Mapping-reversal did not modulate any other effect, including rule-congruency, and therefore indicated rule-congruency unequivocally. Finally, implications concerning generality versus domain specificity of control processes in task switching are discussed.     

Spatial assimilation effects in sequential movements: effects of parameter value switching and practice organization

In Experiment 1, the author extended earlier work by investigating spatial assimilations in sequential aiming movements when participants were able to preplan only the 1st movement of a 2-movement sequence. Right-handed participants (N = 20) aged 18-22 years tried unimanual rapid lever reversals of 20 degrees and 60 degrees with an intermovement interval of 2.5 s. Following the 1st movement, participants made a same-distance movement, different-distance movement, or no movement in a randomly determined order. Participants overshot the short-distance target and undershot the long-distance target for both movements in the sequence, but the errors were greater when the 2nd movement differed from the 1st one. In Experiment 2, right-handed participants (N = 20) demonstrated greater assimilation effects after random practice than after blocked practice of both same-distances (20 degrees -20 degrees and 60 degrees -60 degrees ) and different-distances (20 degrees -60 degrees and 60 degrees -20 degrees ) sequences, although spatial errors were greater in different-distances conditions than in same-distances conditions. Overall, the experiments showed that parameter-value switching and practice organization are 2 major sources of spatial inaccuracy in sequential aiming movements.     

Late backward effects in the refractory period paradigm: effects of Task 2 execution on Task 1 performance

The central bottleneck model assumes that in the psychological refractory paradigm, Task 1 performance is independent of Task 2 demands. Previous studies, however, have reported backward crosstalk effects of motor demands in Task 2 on Task 1 performance. These effects have been attributed to interference at the central level. The present study aimed to isolate more directly potential backward effects at the motor level. Therefore, in three experiments, movement distance in Task 2 was manipulated using a guided ballistic movement. The results showed that movement distance in Task 2 affected reaction time as well as response duration in Task 1. It is argued that the backward effect observed in this study is due to response coupling at motor rather than central levels.     

Orienting in space and time: Joint contributions to exogenous spatial cuing effects

We examined whether the time course of exogenous spatial-cuing effects is sensitive to the allocation of attention in time. Expectation for a target within a particular time window following the cue was manipulated by varying the proportion of trials that appeared at each of three stimulus onset asynchronies in both a detection task and a two-alternative forced-choice discrimination task. The time course of spatial-cuing effects was sensitive to the temporal expectation manipulation only in the discrimination task. The results are discussed with reference to the role of attentional set in exogenous spatialcuing paradigms.     

Effects of state anxiety on performance using a task-switching paradigm: An investigation of attentional control theory

Low- and high-anxious participants performed arithmetical tasks under task-switching or nontask-switching conditions. These tasks were low or high in complexity. The task on each trial was either explicitly cued or not cued. We assumed that demands on attentional control would be greater in the task-switching condition than in the nontask-switching condition, and would be greater with high-complexity tasks than with low-complexity ones. We also assumed that demands on attentional control would be greater when cues were absent rather than present. According to attentional control theory (Eysenck, Derakshan, Santos, & Calvo, 2007), anxiety impairs attentional control processes required to shift attention optimally within and between tasks. We predicted that there would be greater negative effects of high state anxiety in the task-switching condition than in the nontask-switching condition. Our theoretical predictions were supported, suggesting that state anxiety reduces attentional control.     

Inner speech as a retrieval aid for task goals: the effects of cue type and articulatory suppression in the random task cuing paradigm

Articulatory suppression has been shown to increase switch costs in the list paradigm (e.g., [J. Exp. Psychol.: General 130 (2001) 641, J Memory Language 48 (2003) 148]). The present dual-task study examined whether this effect generalizes to the random task cuing paradigm. Participants performed color or shape judgments according to explicit word cues (COLOR or SHAPE) or less transparent letter cues ( C for the color task and S for the shape task). In the word cue condition, the switch cost was equivalent for the articulatory suppression and the control (no dual-task) conditions, but, in the letter cue condition, the switch cost was significantly greater for the articulatory suppression condition than for the control condition. These results suggest that inner speech may be recruited as a tool for retrieving and activating the relevant task goal when the task cue is not transparent and hence imposes nonnegligible retrieval demand.     

Changes in executive control across the life span: examination of task-switching performance

A study was conducted to examine changes in executive control processes over the life span. More specifically, changes in processes responsible for preparation and interference control that underlie the ability to flexibly alternate between two different tasks were examined. Individuals (N = 152) ranging in age from 7 to 82 years participated in the study. A U-shaped function was obtained for switch costs (i.e., the time required to switch between tasks compared with a repeated-task baseline), with larger costs found for young children and older adults. Switch costs were reduced with practice, particularly for children. All age groups benefited from increased preparation time, with larger benefits observed for children and older adults. Adults benefited to a greater extent than children when the interval between the response to one task and the cue indicating which task to perform next was lengthened, which suggested faster decay of interference from the old task set for adults than for children. A series of hierarchical analyses indicated that the age-related variance in task-switching performance is independent, at least in part, from the age-related variance in other cognitive processes such as perceptual speed and working memory. The results are discussed in terms of the development and decline of executive control processes across the life span.     

Stimulus effects on concurrent performance in transition

Six experimentally naive pigeons were exposed to concurrent variable-interval variable-interval schedules in a three-key procedure in which food reinforcement followed pecks on the side keys and pecks on the center key served as changeover responses. In Phase 1, 3 birds were exposed to 20 combinations of five variable-interval values, with each variable-interval value consistently associated with a different color on the side keys. Another 3 pigeons were exposed to the same 20 conditions, but with a more standard procedure that used a nondifferential discriminative stimulus on the two side keys throughout all conditions. In Phase 2, the differential and nondifferential stimulus conditions were reversed for each pigeon. Each condition lasted for one 5-hr session and one subsequent 1-hr session. In the last 14 conditions of each phase, the presence of differential discriminative stimuli decreased the time necessary for differential responding to develop and increased the sensitivity of behavior to reinforcement distribution in the 1st hr of training; during the last hours of training in each condition, however, the effects of the differential discriminative stimuli could not be distinguished from the effects of reinforcement distribution per se. These results show the importance of studying transitions in behavior as well as final performance. They may also be relevant to discrepancies in the results of previous experiments that have used nonhuman and human subjects.     

Cognitive processes in the Extrinsic Affective Simon Task: a task-set switching account of EAST effects

Recently, De Houwer (2003) introduced the Extrinsic Affective Simon Task (EAST) as a new procedure for the indirect assessment of attitudes. In the present paper, we propose an explanation of EAST effects based on a task-set switching account. Specifically, we argue that EAST effects result from difficulties in efficiently switching between two different task sets. Results from two experiments support the assumptions of the task-set switching account: While there were strong EAST effects in task-shift trials, no robust effects were found in task-repetition trials. In Experiment 2, the robustness of this task-shift effect on the EAST was demonstrated: Visual similarity between concept and attribute stimuli did not qualify the task-shift effects. Implications for the interpretation of EAST effects are discussed.     

Attentional switching in the sequential flanker task: age, location, and time course effects

The sequential flanker task was developed to study sequential performance using methodology borrowed from studies of task switching. We investigated age differences in backward inhibition [BI: Mayr, U., & Keele, S. W. (2000). Changing internal constraints on action: The role of backward inhibition. Journal of Experimental Psychology: General, 129, 4-26] during a sequential category search task. Participants learned four animal categories in a fixed order, and then searched for exemplars from those categories in runs of mis-ordered exemplars. Across three experiments, we observed robust BI facilitation effects. However, the magnitude of BI effects did not differ across age groups. This age-invariance held despite manipulations of distractibility (Experiment 2), and interstimulus interval (Experiment 3), suggesting that BI processes may be relatively automatic and obligatory in the context of sequential tasks. The findings are discussed in terms of the attentional mechanisms that underlie task set switching and sequential performance.     

Organization of the bilingual lexicon: Categorical versus alphabetic cuing in Russian-English bilinguals

The mechanism by which Russian native speakers store and retrieve Russian and English words from lexical memory was investigated in two experiments in which fluency of retrieval was compared for categorical and alphabetic cues. We hypothesized that fluency in Russian would be higher for categorical cues but that fluency in English would be higher for alphabetical cues because native language words would have been stored by meaning, while second-language words would have been stored according to dictionary usage. Subjects retrieved more Russian than English words with categorical cues, but their retrieval was the same for the two languages with alphabetic cues. In addition, fluency was greater overall with alphabetical than categorical cues. We attributed the greater fluency in Russian with the categorical cues to the early age at which the concepts were acquired, which made them more accessible in the native language. These findings support the idea that access codes for words may vary depending upon how they are originally learned.This research was supported by Research Grants AFOSR 89-0442 and F49620-92-J-0119 from the U.S. Air Force Office of Scientific Research to Joan Gay Snodgrass. We are indebted to an anomymous reviewer for constructive comments on an earlier version of this article.     

Rules and more rules: The effects of multiple tasks, extensive training, and aging on task-switching performance

Task-switching performance was assessed in young and older adults as a function of the number of task sets to be actively maintained in memory (varied from 1 to 4) over the course of extended training (5 days). Each of the four tasks required the execution of a simple computational algorithm, which was instantaneously cued by the color of the two-digit stimulus. Tasks were presented in pure (task set size 1) and mixed blocks (task set sizes 2, 3, 4), and the task sequence was unpredictable. By considering task switching beyond two tasks, we found evidence for a cognitive control system that is not overwhelmed by task set size load manipulations. Extended training eliminated age effects in task-switching performance, even when the participants had to manage the execution of up to four tasks. The results are discussed in terms of current theories of cognitive control, including task set inertia and production system postulates.     

Action planning in sequential skills: Relations to music performance

The hypothesis that planning music-like sequential actions involves anticipating their auditory effects was investigated in a series of experiments. Participants with varying levels of musical experience responded to each of four colour-patch stimuli by producing a unique sequence of three taps on three vertically aligned keys. Each tap triggered a tone in most experimental conditions. Response–effect (key-to-tone) mapping was either compatible—taps on the top, middle, and bottom keys triggered high, medium, and low pitched tones, respectively—or incompatible—key-to-tone mapping was scrambled, reversed, or neutral (taps on different keys triggered the same tone). The results suggest that action planning was faster with compatible than with incompatible mappings (and faster than with no tones). Furthermore, the size of this compatibility effect grew with increasing musical experience, which suggests that improvements in auditory imagery ability that typically accompany musical training may augment the role of anticipatory auditory-effect representations during planning.     

Action planning in sequential skills: relations to music performance

The hypothesis that planning music-like sequential actions involves anticipating their auditory effects was investigated in a series of experiments. Participants with varying levels of musical experience responded to each of four colour-patch stimuli by producing a unique sequence of three taps on three vertically aligned keys. Each tap triggered a tone in most experimental conditions. Response-effect (key-to-tone) mapping was either compatible—taps on the top, middle, and bottom keys triggered high, medium, and low pitched tones, respectively—or incompatible—key-to-tone mapping was scrambled, reversed, or neutral (taps on different keys triggered the same tone). The results suggest that action planning was faster with compatible than with incompatible mappings (and faster than with no tones). Furthermore, the size of this compatibility effect grew with increasing musical experience, which suggests that improvements in auditory imagery ability that typically accompany musical training may augment the role of anticipatory auditory-effect representations during planning.     

Task switching across the life span: effects of age on general and specific switch costs

The authors investigated age-related changes in executive control using an Internet-based task-switching experiment with 5,271 participants between the ages of 10 and 66 years. Speeded face categorization was required on the basis of gender (G) or emotion (E) in single task blocks (GGG... and EEE...) or switching blocks (GGEEGGEE...). General switch costs, the difference between switching block and single task block performance, decreased during development and then increased approximately linearly from age 18. In contrast, specific switch costs, the difference between switch trial and nonswitch trial performance in the switching block, were more stable across the same age range. These results demonstrate differential age effects in task-switching performance and provide a fine-grained analysis of switch costs from puberty to retirement.     

Cognitive control in number processing: new evidence from number compatibility effects in task-switching

Cognitive Processing - A growing body of research suggests that basic numerical abilities such as number magnitude processing are influenced by cognitive control processes. So far, evidence for...