We had chosen the self-regulation strategy of if-then planning because it has previously been demonstrated to enhance the accessibility of critical items and to automatize the initiation of a respective response (Gollwitzer
& Sheeran, 2006). Accordingly, we expected that planning effects manifest systematically in the parameters of the DSTP model. Indeed, the results of Experiments 1 and 3 support a meaningful match between cognitive processes underlying if-then plans and DSTP model parameters.
First, improved accessibility of the critical item specified in the if-part of an implementation intention is assumed to originate from enhanced percep-tual processing reflected by early and late stages of stimulus selection in the DSTP model. Specifically, the if-part may improve item accessibility through an early processing advantage because the mental representation of a critical item is stronger (e.g., more pre-activated) compared to that of a non-critical item. In the DSTP model, this would be expressed as an enhanced sensory filter in the early stage of stimulus selection, and therefore as an increase in the rate of evidence accumulation (i.e., drift rate) in Phase 1 of response selectionµRS1(i.e., the direct output of the early stage of stimulus selection).
Further, it is possible that improved item accessibility relies on the speeded categorization of the critical item and thus on late attentional selectivity. In the DSTP model, such a recognition advantage would be captured by the drift rateµSS for the late stage of stimulus selection.
Second, strategic automaticity of the instrumental response specified in the thpart of an implementation intention is assumed to reflect an
en-General Discussion 83 hanced link between the critical item and the associated response. Accord-ingly, selection and identification of the critical item immediately trigger the initiation of the relevant response. In the DSTP model, item-response asso-ciations are expressed as rate of response selection in Phase 2, ascribing the then-part effect to an increase of the drift rate µRS2. Another possibility is that the strengthened if-then link also affects the speed of motor commands or early response selection.
Compatible with these considerations, we observed a higher drift rate µRS1for critical targets in a setup which primarily relied on sensory process-ing (Experiment 1) suggestprocess-ing that heightened accessibility of the critical item maps to the efficiency of early stimulus selection in the DSTP model.
Further, implementation intention effects on the drift ratesµSS andµRS2 un-der increased task demands (Experiment 3) indicate that the if-then associ-ation might be primarily captured by late stimulus selection and Phase 2 of response selection. Finally, the insignificant effects on terin both Experiments 1 and 3 speak against a motor-speed-up effect.
Although the DSTP model was not developed in the context of theoretical deliberations on implementation intentions, our results suggest a systematic relation between if-then plans and DSTP parameters. This correspondence between the approaches has important implications for research in the do-mains of implementation intentions and sequential sampling models.
Implications
Beyond supporting the main conclusion that individuals can strategically en-hance information processing efficiency for specific stimuli, our findings show benefits of combining insights from two different research areas: research on implementation intentions, which has primarily been established in the context of social and motivational phenomena, and research on sequential sampling modeling of performance in conflict tasks, which has been devel-oped to explain basic perceptual and attentional mechanisms in information processing and mental control.
Implications for implementation intention research
The present research corroborates prior findings on the processes mediating if-then planning effects on performance (Gollwitzer & Oettingen, 2011) by mapping them onto parameters of a sequential sampling model. Our results further indicate that these processes are moderated by task requirements.
While implementation intention effects were mediated by enhanced item ac-cessibility when the task primarily required sensory processing (Experiment
84 Research Paper II: If-then Planning Enhances Selective Attention 1), the association strength between the critical item and the respective re-sponse emerged as additional mediator when task demands became more complex (Experiment 3).
Moreover, adopting a sequential sampling approach permits new perspec-tives on the processes underlying implementation intentions. First, increased accessibility of a critical item specified in the if-part seems to promote en-hanced information processing during early or late stimulus selection. Our findings suggest however that task complexity is an important moderator:
in non-conflict tasks with one-to-one stimulus-response mapping, early stim-ulus selection is crucial, whereas in conflict tasks with many stimuli and a more complex mapping late stimulus selection comes into play. Second, prior research left open whether the automatic initiation of the response in the then-component results from a heightened associative strength of the then-plan link or from a speed-up in motor commands. Our findings suggest that the first process is more important than the latter.
Implications for sequential sampling approaches
Research using sequential sampling models to delineate cognitive mecha-nisms has provided evidence that the efficiency of information processing (as indexed by the drift rate) is modulated by task difficulty and by largely invariant individual capacities, whereas response thresholds and starting points of evidence accumulation are under strategic control (Ratcliff, 2002;
Voss, Rothermund, & Voss, 2004; Wagenmakers, Ratcliff, Gomez, & McK-oon, 2008, but see, e.g., Dambacher & H¨ubner, 2013, 2015; Rae, Heathcote, Donkin, Averell, & Brown, 2014). While this prevalent view may hold in many circumstances, our results demonstrate that strategic control of pro-cessing efficiency is indeed possible and should therefore be considered in approaches using sequential sampling models.
Our study is also a validation of the dual-stage two-phase (DSTP; H¨ubner et al., 2010) model of selective attention. Extensive research has shown that implementation intention effects are mediated by enhanced item accessibil-ity and the automatic initiation of a goal-directed response (Gollwitzer &
Sheeran, 2006). These processes can be plausibly mapped to components of the DSTP model, and the parameter estimates in Experiments 1 and 3 were sensitive to both processes.
General Discussion 85