Unconscious manipulation of free choice in humans

Previous research has shown that subliminally presented stimuli accelerate or delay responses afforded by supraliminally presented stimuli. Our experiments extend these findings by showing that unconscious stimuli even affect free choices between responses. Thus, actions that are phenomenally experienced as freely chosen are influenced without the actor becoming aware of the manipulation. However, the unconscious influence is limited to a response bias, as participants chose the primed response only in up to 60% of the trials. LRP data in free choice trials indicate that the prime was not ineffective in trials in which participants chose the non-primed response as then it delayed performance of the incongruently primed response.     

Conscious control over the content of unconscious cognition

Visual stimuli (primes) presented too briefly to be consciously identified can nevertheless affect responses to subsequent stimuli - an instance of unconscious cognition. There is a lively debate as to whether such priming effects originate from unconscious semantic processing of the primes or from reactivation of learned motor responses that conscious stimuli afford during preceding practice. In four experiments we demonstrate that unconscious stimuli owe their impact neither to automatic semantic categorization nor to memory traces of preceding stimulus-response episodes, but to their match with pre-specified cognitive action-trigger conditions. The intentional creation of such triggers allows actors to control the way unconscious stimuli bias their behaviour.     

Change detection: evidence for information accumulation in flicker paradigms

Change detection in rapidly alternating pictures separated by a blank frame has been shown to be very difficult (e.g., [Rensink, R. A., O'Regan, J. K., & Clark, J. J. (1997). To see or not to see: The need for attention to perceive changes in scenes. Psychological Science, 8, 368-373]). The three experiments reported here focus on the mechanism behind detection. More specifically, we explored whether information about the stimulus material accumulates in visual memory and thereby improves change detection. For that purpose the first experiment varied the number of repetitions of the original and modified stimulus version. Results showed that detection improved with more repetitions. The second experiment demonstrated that repetition performance improved more when both the original and the modified picture were repeated. Finally, the third experiment strengthened these findings by showing poorer detection performance when the repetition sequence was randomized. Together, our findings suggest accumulation of information in memory over picture presentations and moreover improved performance when both picture types were repeated. These results underline the importance of developing representations for both picture versions in change detection.     

Unconscious priming according to multiple S-R rules

The present study investigated if unconscious primes can be processed according to different stimulus-response (S-R) rules simultaneously. Participants performed two different S-R rules, such as judging a digit as smaller or larger than five and judging a letter as vowel or consonant. These S-R rules were administered in random order and announced by a previously presented cue. Each target stimulus was preceded by subliminal primes which afforded a different or an identical response according to either the currently irrelevant or currently relevant S-R rule. In three experiments, we consistently found priming effects according to currently irrelevant S-R rules, even when primes for the relevant and irrelevant S-R rules were presented simultaneously. Thus, unconscious stimuli have the power to activate responses according to currently required and currently not required S-R rules concurrently. The results are in line with response activation accounts of subliminal priming and suggest that at least two routes may gain access on response processes simultaneously.     

Conflict monitoring and the affective-signaling hypothesis—An integrative review

Psychonomic Bulletin & Review - Conflict-monitoring theory proposes that conflict between incompatible responses is registered by a dedicated monitoring system, and that this conflict signal...     

Adaptive control of ideomotor effect anticipations

According to ideomotor theory, voluntary actions are selected and initiated by means of anticipated action effects. Prior experiments yielded evidence for these effect anticipations with response-effect (R-E) compatibility phenomena using blocked R-E relations. Daily actions, however, typically evoke different effects depending on the situational context. In the present study, we accounted for this natural variability and investigated R-E compatibility effects by a trial-by-trial variation of R-E compatibility relations. In line with recent observations regarding ideomotor learning, R-E compatibility influenced responding only when participants responded in free choice trials assuming that participants then adopted an intention-based action control mode. In contrast, R-E compatibility had no impact when participants responded according to imperative stimuli throughout the experiment, thus when participants adopted a stimulus-based action control mode. Interestingly, once an intention-based mode was established because of free choice trials within an experimental block, we observed response compatibility effects in free as well as forced choice trials. These findings extend and refine theoretical assumptions on different action control modes in goal-directed behavior and the specific contribution of ideomotor processes to intention-based action control.     

Time perception and the experience of agency

In the current study, we investigate whether sense of agency over an effect coincides with the perceived time of the effect that occurs either at its usual time or earlier or later than usual. One group of participants usually perceived an action effect immediately after the action, another group delayed by 250 ms. In test blocks the effect stimulus was sometimes presented earlier or later than usual. Participants judged either the degree of experienced agency over the effect or whether the effect had appeared at its usual time, or earlier or later than usual. In both groups experienced agency and the perception of the effect’s time ‘as usual’ were highly correlated. To rule out that time judgments influenced sense of agency, we replicated the pattern of agency judgments in Experiment 2 in which participants only judged agency. Taken together, we demonstrated that agency and time judgments vary similarly across temporal deviations of effects irrespective of to which delay participants were adapted to. The high correlation of judgment types indicates that perceiving an effect at its usual time and sensing to have caused the effect are closely related. In contrast, physical temporal proximity of actions and effects has only a minor impact on experienced agency.     

Dorsal and ventral processing under dual-task conditions

It is widely acknowledged that visual input is processed along two anatomically and functionally distinct pathways--a ventral pathway for conscious perception and a dorsal pathway for action control. The present study investigated whether the apparent direct and unmediated processing in the dorsal stream is subject to capacity limitations. Specifically, we tested whether a simple dorsal task of grasping an object is affected by the psychological refractory period (PRP), a well-known indication of capacity limitations. Subjects performed an auditory choice reaction task and then, following varying delays, had to judge an object's width (ventral task) or grasp an object across its width (dorsal task). Although these tasks were differentially affected by irrelevant variation of the objects' length, they were subject to comparable dual-task interference. These results show that despite important differences between ventral and dorsal information processing, both modes of processing are constrained by limited capacities.     

Explorations of anticipatory behavioral control (ABC): a report from the cognitive psychology unit of the University of Würzburg

The report comprises recent theoretical considerations, experimental research, and simulations which all aim at a clarification of anticipatory mechanisms of behavioral control.     

Intentional Binding is independent of the validity of the action effect's identity

When an action produces an effect, both events are perceived to be shifted in time toward each other. This shift is called Intentional Binding (IB) effect. First evidence shows that this shift does not depend on the statistical predictability of the produced effect's identity (Desantis, Hughes, & Waszak, 2012). We confirm this result by comparing the perceived duration of action–effect intervals before valid and invalid action effects using the method of constant stimuli. The perceived duration of action–effect intervals did not differ for valid and invalid effects. This result was true for different durations of the action–effect interval (Experiments 1–4: 250 ms, Experiments 1 & 2: 400 ms), different effect modalities (Experiments 1 & 3: visual, Experiments 2–4: auditive), and two types of validity variations (Experiments 1 & 2: 80% valid, Experiments 3 & 4: 100% valid vs. random). We validated our results by using a clock paradigm and a numerical duration estimation task (Experiment 4). We conclude that the IB effect is not the result of internal prediction due to action–effect bindings, but might rely on higher-order processes.