Research Statement  – Psychological Processes through the Lens of Physical Actions

Much of what we do concerns the use of our action systems to interact with the world, including interactions with others around us. Without the ability to act, our psychological processes would merely be spectators. What is the use of having thoughts and emotions if not for our ability to translate them into adaptive changes to our environment? While a common definition for the field of psychology as “the study of mental life and behavior” may falsely suggest that mental life and behavior are somewhat separate entities, my research aims to elucidate how we use our action systems in support of psychological processes. These processes include cognitions underlying action planning and coordination in individual contexts, as well as social cognitive processes that come into play when we perceive, plan, and coordinate with others around us.

A better understanding of action cognition in general is useful for fields as wide-ranging as psychology, neuroscience, philosophy, robotics, physical rehabilitation, and engineering. When people have suffered from a stroke, they have trouble with the planning of actions. A better understanding could inform rehabilitation. In robotics, building socially cognizant robots has proven difficult due in part to the limited knowledge we have on action planning. In philosophy, a great deal of theorizing concerns how our physical actions relate to our mental experiences. My research projects touch on these issues through carefully controlled experiments.

My general approach is to understand a range of psychological processes through the lens of physical actions. Through this approach, I have contributed understanding to basic motor control, to cognitive mechanisms for action planning and coordination within and across individuals, to disturbances in action planning in Parkinson Disease (PD), to the link between perception and action, to face processing, and to abstract issues relating to the sense of agency and the tracking of others’ belief states. My work has involved a wide range of methods (including motion analysis, force analysis, reaction time measures, computational modeling, and eye tracking), as well as different populations (healthy adults, children, and PD patients).

Acting in a Social World

Most of my current research focuses on planning and coordinating our own actions with those of others, including actions such as carrying furniture, building bridges, playing sports, and dancing together. Despite how pervasive these joint actions are, we still have a limited understanding of how people plan and coordinate their actions together, as well as how people derive a sense of control and agency over joint actions.

Higher-level processes through the lens of action

Philosophers have long been interested in the link between physical actions and our subjective experience of control (sense of agency) over such actions. Few experiments have addressed how we derive a sense of agency during joint actions (but see van der Wel, Sebanz, & Knoblich, 2012, Journal of Experimental Psychology: Human Perception & Performance, for an early example). To investigate this issue, I have developed a core paradigm (van der Wel, 2015, Cognition) that allows for the systematic manipulation of actions and their effects in a dyadic joint action task while recording each action partner’s objective action contributions. By varying role distributions and levels of objective control, this task is ideally suited to gain a better understanding of the sense of agency and its measures in joint action contexts. I am currently waiting to hear back from NSF on a full proposal with co-PI Pernille Hemmer that contains a series of experiments, measures, and computational modeling approaches to better understand the sense of agency, in particular for joint actions. I am also collaborating with researchers at the University of Wuerzburg to understand the sense of agency in sequential contexts rather than based on single, isolated actions.

Another line of work on higher-level processing concerns how our own and others’ beliefs influence our actions. In this belief tracking project, I use a computer mouse tracking paradigm and study the mouse movement kinematics to determine how belief representations compete. While computational modeling suggests that there are limits to using mouse trajectories for inferring discrete versus continuous processing systems (van der Wel et al., 2009, JEP:HPP), this method offers the advantage of providing an evolution of data points rather than a single data point per trial. With this method, we showed that people represent their own and another agent’s belief automatically and in parallel, even without an objective reason to do so (van der Wel et al., 2014, Cognition). I am currently testing how the veridicality of one’s own and others’ beliefs influences overt behavior in this task.

Coordinating with others in real-time

Many actions people perform together rely on intricate coordination between two or more people. Thus, one issue concerns how we incorporate others’ actions to adjust the timing of our own actions to accomplish joint action goals. In a set of tasks, we found that people use their own motor system to predict their own and others’ timing to coordinate. Interestingly, participants achieved such coordination exclusively through adjustments by the person with the less demanding task (Vesper, van der Wel, Sebanz, & Knoblich, 2011, Experimental Brain Research; 2013, JEP:HPP).

Another issue concerns how different modalities contribute to joint action coordination. Because people inherently lack full information during such actions (compared to acting alone), they may compensate by seeking information exchange through additional modalities in the service of coordination. To examine this, we (van der Wel, Sebanz, & Knoblich, 2011, JEP:HPP) had individuals and dyads learn a coordination task in which they moved a pendulum back and forth between two targets by pulling on strings. In this task, participants could create a haptic information exchange by pulling on both strings simultaneously (as this creates a physical link). Dyads learned the task at the same rate as individuals but used haptic information much more so than when an individual performed the same task bimanually. Dyads may thus differentially tune into different modalities to coordinate successfully with others, which could help them to compensate for lacking complete internal information about joint actions. Much more work is needed on how dyads use different modalities, and on how planning and execution processes interact for the wide range of joint actions people perform.

Planning for and alongside others

When we act together, we may plan actions in ways that facilitate our action partners. One could see this when handing over scissors to someone else, but in that case, we have been taught not to point the blade towards the action’s recipient. Do people accommodate others’ actions in general? We (van der Wel, Meyer, & Hunnius, 2013, EBR) tested this possibility by asking two people to manipulate a novel object together. We found that participants indeed adjusted how they handed over an object to their action partner depending on their action partner’s subsequent task. We have also shown in a collaborative task how this social ability develops early in life, by testing young children on their action planning abilities as well as on their use of anticipatory eye movements (Meyer, van der Wel, Hunnius, 2016, Proceedings of the Royal Society, B).

While the previous example suggests that we modify our own actions when we interact with others, a large body of work has also established an influence of other people’s actions on our own actions. For example, during continuous movement sequences actors entrain to the movements of others. Studies on co-representation that use discrete actions show that people also form representations of a co-actor’s task. While these phenomena come from separate literatures, we (van der Wel & Fu, 2015, Psych Bulletin & Review) showed how entrainment and co-representation can occur within a single task paradigm, by showing that participants moved higher in a back-and-forth movement task when a confederate next to them cleared an obstacle than when they did not. For continuous movements, this effect depended on the availability of visual information, as would be expected based on entrainment. Consistent with co-representation, the co-actor’s task modulated the height of discrete movements regardless of the availability of visual information. These results highlight the importance of a proper understanding of principles of motor control to gain a full understanding of action cognition. The results also show that both dynamical system principles and representational principles have a place in accounting for joint action cognition.

Using social and non-social facial cues to support interaction

Representing others is a fundamental part of social cognition. Aside from action-related information, we also process many other behavioral displays of those around us to align our own actions. One such example is processing of others’ facial expressions. In this context, we conducted several studies on how cues related to eye gaze influence attentional processing in a perceiver. While this work does not directly address joint action, it focuses on mechanisms that could support successful interaction. In this regard, we have shown that attention is broadly captured by gaze direction and shifts in gaze direction (e.g., Bockler, van der Wel, & Welsh, 2014, Psych Science). In a sequence of follow up experiments, we have also shown that these effects on attention depend on holistic face processing (Bockler et al, 2015, Acta Psychologica; van der Wel et al., 2018, APP), as well as on the emotion expression on the face (Pittig et al, 2022, JEP:HPP; Breil et al, in press, Emotion).We are currently testing whether pareidolia faces (i.e., faces composed of objects) invoke similar attentional effects, and whether and how gaze effects and emotion expression interact with identity-related aspects of the face, including biological sex and presumed gender identity. 

Acting Alone

The work described so far focuses on action cognition in social contexts. I am also still involved in some more basic work on action cognition that I started during by doctoral studies. Some of this work focuses on object manipulation tasks, with the purpose to determine how people plan relatively simple physical actions (van der Wel & Rosenbaum, 2007, ERB, 2010, EBR; van der Wel, Huhn, & Schimpf, 2014, ERB; Rosenbaum, Chapman, Weigelt, Weiss, & van der Wel, 2012, Psychological Bulletin). Other experiments have focused on how people plan action sequences (Fritsche, van der Wel, Smit, Bloem, Toni, & Helmich, 2020, eNeuro; van der Wel, Fleckenstein, Jax, & Rosenbaum, 2007, JEP:HPP). This line of work relied extensively on motion tracking and included both healthy participants and patients suffering from Parkinson’s Disease. I am currently still using motion tracking analysis to investigate the control of movement rate (van der Wel, Rosenbaum, & Sternad, 2010, Journal of Motor Behavior). I showed previously that people have a preferred movement rate, and that they engage in strategies to avoid moving below their preferred rate for arm movements. Understanding slowing of movements is important as it occurs in for example stroke patients and PD patients. I am currently continuing this work through a funded collaboration with Dr. Jason Friedman at Tel Aviv University.

In Closing

I started this statement by indicating my interest in studying psychological processes through the lens of physical actions. My work indicates that some of these processes concern the actual planning of actions themselves. Knowledge on this topic has both theoretical and applied value. My work on acting with others indicates that the planning and coordination involved in joint action is remarkably complex. Part of the goal of that line of work is to elucidate just how people achieve such actions successfully. Theoretically, this work takes an embodied cognition approach (see Witt & van der Wel, in press, chapter; van der Wel, Sebanz, & Knoblich, 2016, chapter). There has been a tradition in cognitive psychology to study the mind by asking people do complete tasks by themselves. Starting at the interpersonal level provides a fundamentally different view on the question of how our minds are shaped. My work on higher-level processes further takes the notion that cognition is both for acting in an individual and in a social world seriously. From my work on joint agency, it seems that we could truly be in it together.