Abstract: Model-based assessments of behavioral control have been used to study the acute effects of alcohol on the ability to execute and inhibit behavioral responses. Response inhibition appears more vulnerable to the impairing effects of alcohol than response execution. Current information processing models have yet to account for this observation. Objectives: The present study used a reductionist approach to determine if the particular vulnerability of response inhibition to the effects of alcohol occurs at the level of the action (motor program). The study examined the effects of alcohol on the ability to execute and inhibit behavior in a context in which preliminary information signaled the likelihood that a response should be executed or suppressed. The engagement and disengagement of responses were directly compared under alcohol. Methods: Adults (N=24) performed a cued go/no-go task that required quick responses to go targets and suppression of responses to no-go targets. Response requirements were manipulated by varying the nature of the action required whereby half of the participants made key press responses (response engagement) and the other half released ongoing key presses (response disengagement). Performance was tested under three doses of alcohol: 0.00, 0.45, and 0.65 g/kg. Results: Dose-dependent increases in commission errors were only observed with response engagement and not with response disengagement. Reaction times were faster for response engagement than response disengagement. Conclusions: Response disengagement affords some protection against alcohol-induced impairment of inhibition, indicating that not all aspects of motor processing requiring inhibition are equally impaired by alcohol.
Abstract: Practice can, in some cases, largely eliminate measured dual-task interference. Does this absence of interference indicate the absence of a processing bottleneck (defined as an inability to carry out certain stages in parallel)? The authors show that a bottleneck need not produce any observable interference, provided that there is no temporal overlap in the demand for bottleneck stages on the 2 tasks. Such a "latent" bottleneck is especially likely after practice, when central stages are short. The authors provide new evidence that a latent bottleneck occurred for a participant who produced no interference in Van Selst, Ruthruff, and Johnston (1999). These findings demonstrate that the absence of dual-task interference does not necessarily indicate the absence of a processing bottleneck.
Abstract: This study tested the degree that alcohol restricts information processing on tasks requiring response execution and response suppression. A dual task required 12 participants to respond to 2 task stimuli (Tasks 1 and 2) presented in close succession. The task was performed before and after receiving 3 alcohol doses (placebo, 0.45 g/kg, and 0.65 g/kg) administered on separate days in a counterbalanced order. Alcohol increased task interference, as evidenced by increased time to respond to Task 2. Impairment was comparable regardless of whether Task 1 required a response to be executed or suppressed. The evidence supports a resource limitation account that argues that alcohol reduces capacity to process information required for execution and suppression of responses.
Abstract: M. A. Van Selst, E. Ruthruff, and J. C. Johnston (1999) found that practice dramatically reduced dual-task interference in a Psychological Refractory Period (PRP) paradigm with 1 vocal response and 1 manual response. Results from 3 further experiments using the highly trained participants of M. A. Van Selst et al. (1999) support 4 main conclusions: (a) A processing bottleneck exists even after extensive practice; (b) the principal cause of the reduction in PRP interference with practice is shortening of Task 1 bottleneck stages; (c) a secondary cause is that 1 or more, but not all, of the Task 2 substages that are postponed before practice are not postponed after practice (i.e., become automatized); and (d) the extent of PRP reduction with practice depends on the modalities of the 2 responses. A control experiment with 2 manual response tasks showed less PRP reduction with practice than that found by Van Selst et al.