Markus Janczyk

Confidence intervals for two sample means: Calculation, interpretation, and a few simple rules.

Valued by statisticians, enforced by editors, and confused by many authors, standard errors (SEs) and confidence intervals (CIs) remain a controversial issue in the psychological literature. This is especially true for the proper use of CIs for within-subjects designs, even though several recent publications elaborated on possible solutions for this case. The present paper presents a short and straightforward introduction to the basic principles of CI construction, in an attempt to encourage students and researchers in cognitive psychology to use CIs in their reports and presentations. Focusing on a simple but prevalent case of statistical inference, the comparison of two sample means, we describe possible CIs for between- and within-subjects designs. In addition, we give hands-on examples of how to compute these CIs and discuss their relation to classical t-tests.

Effective Rotations: Action Effects Determine the Interplay of Mental and Manual Rotations

The last decades have seen a growing interest in the impact of action on perception and other concurrent cognitive processes. One particularly interesting example is that manual rotation actions facilitate mental rotations in the same direction. The present study extends this research in two fundamental ways. First, Experiment 1 demonstrates that not only manual rotations facilitate mental rotations but that mental rotations also facilitate subsequent manual rotations. Second, Experiments 2 and 3 targeted the mechanisms underlying this interplay. Here, manual steering wheel rotations produced salient visual effects, namely the rotation of either a plane or a horizon in an aviation display. The rotation direction of these visual effects either did or did not correspond to the direction of the manual rotation itself. These experiments clearly demonstrate an impact of sensory action effects: Mental rotations facilitate manual rotations with visual effects of the same direction (as the mental rotation), irrespective of the direction of the manual rotation. These findings highlight the importance of effect anticipation in action planning. As such they support the contentions of ideomotor theory and shed new light on the cognitive source of the interplay between visual imagery and motor control.

Who is talking in backward crosstalk? Disentangling response- from goal-conflict in dual-task performance

Responses in the second of two subsequently performed tasks can speed up compatible responses in the temporally preceding first task. Such backward crosstalk effects (BCEs) represent a challenge to the assumption of serial processing in stage models of human information processing, because they indicate that certain features of the second response have to be represented before the first response is emitted. Which of these features are actually relevant for BCEs is an open question, even though identifying these features is important for understanding the nature of parallel and serial response selection processes in dual-task performance. Motivated by effect-based models of action control, we show in three experiments that the BCE to a considerable degree reflects features of intended action effects, although features of the response proper (or response-associated kinesthetic feedback) also seem to play a role. These findings suggest that the codes of action effects (or action goals) can become activated simultaneously rather than serially, thereby creating BCEs.

The Locus of Tool-Transformation Costs

Transformations of hand movements by tools such as levers or electronic input devices can invoke performance costs compared to untransformed movements. This study investigated by means of the Psychological Refractory Period (PRP) paradigm at which stage of information processing such tool-transformation costs arise. We used an inversion transformation, that is, the movement of the operating hand was transformed into a spatially incompatible movement of a lever. As a basic tool-transformation effect, the initiation of inverted tool movements was delayed compared to noninverted movements. Experiment 1 suggested a central (or postcentral) locus of this tool-transformation effect and ruled out a (precentral) perceptual locus. Experiments 2 and 3 confirmed the central locus and ruled out a later, motor-related stage of processing. The results show that spatially incompatible tool movements delay a capacity-limited stage of information processing, often referred to as response selection.

Visual and tactile action effects determine bimanual coordination performance

Effect-based models of motor control assign a crucial role to anticipated perceptual feedback in action planning. Two experiments were conducted to test the validity of this proposal for discrete bimanual key press responses. The results revealed that the normally observed performance advantage for the preparation of two responses with homologous rather than non-homologous fingers becomes inverted when homologous fingers produce non-identical visual effects, and non-homologous fingers produce identical visual effects. In the second experiment the finger homology effect was strongly reduced when homologous fingers produced non-identical tactile feedback. The results show that representations of to-be-produced visual and tactile action effects both contribute to action planning, though possibly to a varying degree. Implications of these results for effect-based models of motor control are considered.

Good things peak in pairs: a note on the bimodality coefficient.

Frequency data of four hypothetical distributions of 100 values each, with corresponding estimates of skewness (m3), kurtosis (m4), and the BC.

Good vibrations? Vibrotactile self-stimulation reveals anticipation of body-related action effects in motor control

Previous research suggests that motor actions are intentionally generated by recollecting their sensory consequences. Whereas this has been shown to apply to visual or auditory consequences in the environment, surprisingly little is known about the contribution of immediate, body-related consequences, such as proprioceptive and tactile reafferences. Here, we report evidence for a contribution of vibrotactile reafferences to action selection by using a response–effect compatibility paradigm. More precisely, anticipating actions to cause spatially incompatible vibrations delayed responding to a small but reliable degree. Whereas this observation suggests functional equivalence of body-related and environment-related reafferences to action control, the future application of the described experimental procedure might reveal functional peculiarities of specific types of sensory consequences in action control.

The benefit of no choice: goal-directed plans enhance perceptual processing

Choosing among different options is costly. Typically, response times are slower if participants can choose between several alternatives (free-choice) compared to when a stimulus determines a single correct response (forced-choice). This performance difference is commonly attributed to additional cognitive processing in free-choice tasks, which require time-consuming decisions between response options. Alternatively, the forced-choice advantage might result from facilitated perceptual processing, a prediction derived from the framework of implementation intentions. This hypothesis was tested in three experiments. Experiments 1 and 2 were PRP experiments and showed the expected underadditive interaction of the SOA manipulation and task type, pointing to a pre-central perceptual origin of the performance difference. Using the additive-factors logic, Experiment 3 further supported this view. We discuss the findings in the light of alternative accounts and offer potential mechanisms underlying performance differences in forced- and free-choice tasks.

Instant attraction: immediate action-effect bindings occur for both, stimulus- and goal-driven actions.

Flexible behavior is only possible if contingencies between own actions and following environmental effects are acquired as quickly as possible; and recent findings indeed point toward an immediate formation of action-effect bindings already after a single coupling of an action and its effect. The present study explored whether these short-term bindings occur for both, stimulus- and goal-driven actions (“forced-choice actions” vs. “free-choice actions”). Two experiments confirmed that immediate action-effect bindings are formed for both types of actions and affect upcoming behavior. These findings support the view that action-effect binding is a ubiquitous phenomenon which occurs for any type of action.

Thinking with portals: Revisiting kinematic cues to intention

What we intend to achieve with our actions affects the way we move our body. This has been repeatedly shown for both, movement-related intentions such as grasping and turning an object, and relatively high-level intentions such as the intention to collaborate or to compete with a social partner. The impact of an intermediate level of intentions - referring to action-contingent changes in the physical environment - is far less clear, however. We present three experiments that aim at scrutinizing this level of analysis by showing how such anticipated consequences affect movement trajectories. Participants steered a virtual avatar toward portals that displaced the avatar to a different but predictable location. Even though this displacement occurred only after the movement was completed, hand movements were clearly torn toward the anticipated final location of the avatar. These results show that properties of anticipated action consequences leave a fingerprint on movement trajectories and provide an opportunity to unite previous accounts on the relation of intentions and movements with general frameworks of action planning.