Allocation of effort as a function of payoffs for individual tasks in a multitasking environment

SYNWORK1 software allows the examination of how payoffs affect the allocation of effort by people when they perform four different tasks (memory search, arithmetic, visual monitoring, and auditory monitoring). In a previous study (Wang, Proctor, & Pick, 2007), we showed that participants adopted multitasking strategies allocating relative effort appropriate to payoff differences between the arithmetic and memory tasks, but that they exhibited residual effects of prior payoffs when the payoffs were switched. In the present study, we varied the payoff in two different experiments for only one of these tasks, the memory task in Experiment 1 and the arithmetic task in Experiment 2. Doing this allowed consideration of performance for both the task for which payoff changed explicitly and the other cognitive task, for which the payoff difference was implicit (i.e., relative to the explicit payoff that was manipulated). Although participants adjusted performance on the task for which the payoff explicitly varied, the payoff manipulation had less effect than did the explicit payoff manipulations for both tasks used previously. Also, the change in effort on a task resulting from explicitly increasing its payoff was less than that from decreasing the payoff. SYNWORK1 is a good environment for studying multitasking, but has several limitations that need to be addressed to provide a synthetic work environment that allows investigation of a wider range of theoretically relevant issues.     

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.     

Multidimensional vector model of stimulus-response compatibility

The present study proposes and examines the multidimensional vector (MDV) model framework as a modeling schema for choice response times. MDV extends the Thurstonian model, as well as signal detection theory, to classification tasks by taking into account the influence of response properties on stimulus discrimination. It is capable of accounting for stimulus-response compatibility, which is known to be an influential task variable determining choice-reaction performance but has not been considered in previous mathematical modeling efforts. Specific MDV models were developed for 5 experiments using the Simon task, for which stimulus location is task irrelevant, to examine the validity of model assumptions and illustrate characteristic behaviors of model parameters. The MDV models accounted for the experimental data to a remarkable degree, demonstrating the adequacy of the framework as a general schema for modeling the latency of choice performance. Some modeling issues involved in the MDV model framework are discussed.     

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.     

Stroop-like serial position effects in color naming of words and nonwords

Color-naming latencies to noncolor words and nonwords were faster when the onset or final phoneme of the displays corresponded to the onset or final phoneme of the color response. For example, for displays printed in red, the word rack and nonword rask, which share the initial onset phoneme with the response, led to faster naming than did the control word chap and nonword chup. Conversely, when the onset or final phoneme of the displays matched the onset or final phoneme of a conflicting color response (e.g., rack printed in blue), latencies were longer than to control items. Facilitation effects were stronger than interference effects, and the onset phoneme facilitation effect was augmented by coloring only the initial letter in the display. It is hypothesized that nonlexical processes that govern the translation of print to speech may be a source of facilitation in Stroop-like tasks, whereas lexical processes are more likely to contribute to interference.     

Stroop dilution depends on the nature of the color carrier but not on its location

Stroop dilution is the reduction of the Stroop effect in the presence of a neutral word. It has been attributed to competition for attention between the color word and neutral word, to competition between all stimuli in the visual field, and to perceptual interference. Five experiments tested these accounts. The critical manipulation was whether the color to be named was carried by the color word or the neutral word. Neutral words diluted the Stroop effect when they were the color carrier, but not when the color word was the color carrier. We argue that Stroop dilution is due to attentional competition between the color word and neutral word, with priority given to the color carrier.     

Neuropsychological Performance in Gulf War Era Veterans: Motivational Factors and Effort

Assuming that the underlying etiology of unexplained health-related symptoms in returning Gulf War (GW) veterans is multifactorial, the possible role of feigning or exaggeration of symptoms is worth consideration as a contributing factor. The present study assessed the relationship between motivation to perform well during neuropsychological assessment and objective neuropsychological test performance. Motivation was measured as the score on a visual memory task (Test of Memory Malingering, TOMM) of low difficulty. Participants included 77 veterans from the cohorts of GW- (n = 58) and Germany-deployed (n = 19) GW-era veterans described in two other papers in this issue who were administered the TOMM. Most veterans earned perfect or near-perfect scores on the TOMM (48–50/50). Scores 47 were associated with lower scores on neuropsychological tasks assessing attention, executive functions, and memory. Variability in test performance within and between tasks measuring similar functions was also found in participants with lower TOMM scores.     

Display-control arrangement correspondence and logical recoding in the Hedge and Marsh reversal of the Simon effect

When left and right keypresses are made to stimuli in left and right locations, and stimulus location is irrelevant to the task, responses are typically faster when stimulus location corresponds with response location than when it does not (the Simon effect). This effect reverses when the relevant stimulus-response mapping is incompatible, with responses being slower when stimulus and response locations correspond (the Hedge and Marsh reversal). Simon et al. (Acta Psychol. 47 (1981) 63) reported an exception to the Hedge and Marsh reversal for a situation in which the relevant stimulus dimension was the color of a centered visual stimulus and the irrelevant location information was left or right tone location. In contrast, similar experiments have found a reversal of the Simon effect for tone location when relevant visual locations were mapped incompatibly to responses. We conducted four experiments to investigate this discrepancy. Both results were replicated. With an incompatible mapping, irrelevant tone location showed a small reverse Simon effect when the relevant visual dimension was physical location but not when the color of a centered stimulus or the direction in which an arrow pointed conveyed the visual location information. The reversal occurred in a more standard Hedge and Marsh task in which the irrelevant dimension was location of the colored stimulus, but only when the response keys were visibly labeled. Several of the results suggest that display-control arrangement correspondence is the primary cause of the Hedge and Marsh reversal, with logical recoding playing only a secondary role.