naturalistic experimental setup for studying real-world human actions

A Setup for Human Vision, Cognition, and Interaction in Real-Life Scenarios

A fundamental skill for survival and social interaction is the ability to perceive and make sense of others&#39; actions and interact with them in the surrounding environment. Previous research in the last several decades has made significant contributions to understanding the fundamental principles of how individuals perceive and understand others&#39; actions1,2,3,4,5,6,7,8,9,10,11. Nevertheless, given the complexity of interactions and the circumstances in which they occur, there is an obvious need to further develop the body of knowledge in naturalistic settings in order to reach a more complete understanding of this complex skill in daily life settings.
In natural environments such as our daily life settings, perception and cognition exhibit embodied, embedded, extended, and enactive characteristics12. In contrast to internalist accounts of brain functions that tend to understate the roles of the body and the environment, contemporary approaches to embodied cognition focus on the dynamic coupling of the brain, body, and environment. On the other hand, most social psychology, cognitive psychology, and neuroscience research on action perception tend to assume that utilizing well-controlled and simplified experiment designs in laboratory conditions (e.g., images or videos in computerized tasks) yields results that can be generalized to more complex scenarios such as real-world interactions1,2,3,4,5,6,7,8,9,10,11. This assumption guarantees that robust and reliable data can be obtained under many circumstances. Nevertheless, a well-known challenge is that the validity of the models derived from carefully controlled experiments is limited when tested in a real-world context13. Consequently, further investigations13,14,15,16,17,18,19,20,21,22 have been conducted to address the ecological and external validity of stimuli and experimental designs in various fields of research.
In this study, a novel method is suggested for investigating how individuals perceive and evaluate others&#39; actions by using live actions performed by a real, physically present actor. Scenarios similar to real-life contexts are employed, while the experimenters have control over possible confounding factors. This study is a form of &#34;naturalistic laboratory research&#34;, within the framework of Matusz et al.14&#160;which can be conceived as an intermediate stage between &#34;classic laboratory research&#34;, which makes use of maximal control over the stimuli and environment, often at the expense of naturalness, and &#34;fully naturalistic real-world research&#34;, which aims to maximize naturalness at the expense of control over the stimulation and the environment14. The study aims to address the need for empirical investigations at this level in action perception research in order to bridge the gap between the findings obtained in traditional laboratory experiments with a high degree of experimental control and the findings obtained in studies conducted in entirely unconstrained, natural settings.
Controlled versus unconstrained experiments 
Experimental control is an efficient strategy for designing experiments to test a specific hypothesis, as it allows researchers to isolate target variables from likely confounding factors. It also allows for revisiting the same hypothesis with certain levels of amendments, such as using slightly or totally different stimuli in the same design or testing the same stimuli in alternative experimental setups. Systematic investigation through controlled experiments is a traditional form of methodology in research in cognitive science and relevant domains. Controlled experiments still help to establish the body of knowledge on the fundamental principles of cognitive processes in various domains of research, such as attention, memory, and perception. However, recent research has also acknowledged the limitations of traditional laboratory experiments in terms of generalizing the findings to real-world settings, and researchers have been encouraged to conduct studies in enhanced ecological settings13,14,15,16,17,18,19,20,21. This shift aims to address two important issues regarding the discrepancy between traditional laboratory experiments and real-world settings. First, the world outside the laboratory is less deterministic than in experiments, which limits the representative power of systematic experimental manipulations. Second, the human brain is highly adaptive, and this is often underestimated due to the practical limitations of designing and conducting experimental studies22. The concept of &#34;ecological validity&#34;23,24 has been used to address methods for resolving this issue. The term is usually used to refer to a prerequisite for the generalization of experimental findings to the real world outside the laboratory context. Ecological validity has also been interpreted as referring to validating virtually naturalistic experimental setups with unconstrained stimuli to ensure that the study design is analogous to real-life scenarios25. Due to the high degree of variance in the interpretation of this term, an understanding of the advantages and limitations of alternative methodologies and stimulus selection is required.
Levels of naturalism in stimuli and experiment design 
Previous work in experimental psychology and cognitive neuroscience has used a wide range of stimuli with different levels of naturalism26. Most researchers prefer to use static images or short dynamic videos because these stimuli are easier to prepare than those that could simulate a real action or an event. Despite having advantages, these stimuli do not allow researchers to measure contingent behaviors among social agents. In other words, they are not actable and do not have social affordance27. In recent years, an alternative to these non-interactive stimuli has been developed: real-time animations of virtual avatars. These avatars allow for the investigation of the interactions between avatars and their users. However, the use of virtual avatars is subject to reduced user apprehension, especially when they do not appear particularly engaging in terms of their realistic and contingent behaviors26. Therefore, there is now more interest in using real social stimuli in experimental studies. Although their design, data recording, and analysis may require advanced equipment and complex data analysis, they are the best candidates for understanding naturalistic human behavior and cognition.
The present study proposes a methodology for using real-life social stimuli in a laboratory environment. This study aims to investigate how people perceive and evaluate others&#39; actions in a setting with enhanced ecological validity compared to traditional laboratory experiments. We have developed and described a novel setup in which participants are exposed to real actors who are physically present and share the same environment with them. In this protocol, the participants&#39; response times and mouse trajectories are measured, which requires precise timing of the stimuli presentation and strict control over the experimental conditions in this enhanced ecological setting. Therefore, the experimental paradigm stands out among the frameworks present in the literature since the naturalness of the stimuli is maximized without sacrificing control over the environment. Below, the protocol presents the steps to establish such a system and then continues with the representative results for the sample data. Finally, a discussion of the paradigm&#39;s significance, limitations, and plans for modifications is presented.
Experimental design 
Before proceeding to the protocol section, we describe the parameters used in the present study and present the details of the stimuli together with the experimental design.
Parameters in the study 
This study aims to measure how the type of actor and the class of actions they perform affect the mind perception processes of the participants. In the protocol, the mind perception process is measured in two main dimensions, namely agency and experience, as proposed by previous research28. The high and low ends of these two dimensions are also included, as recently introduced by Li et al.29.
The structure of the study was inspired by the single-category version30 of the commonly used implicit association task (IAT)31. In this task, the response times of the participants while they match an attribute concept with the target concept are used as an indication of the strength of their implicit associations for these two concepts. In the adaptation of this implicit task, the participants are presented live actions performed by real actors and required to match them to&#160;target concepts. The target concepts are the high and low ends of the agency or experience dimensions, depending on the block of the experiment.
To summarize, the independent variables are Actor Type and Action Class. Actor Type has two levels (i.e., two different actors, Actor1 and Actor2, performing in the study). Action Class has two levels: Action Class1 and Action Class2, and each class contains four actions. The participants evaluate the two actors separately in four blocks (one actor in each block), and in each block, the actors perform all of the actions in a counter-balanced order. The participants perform evaluations with respect to two pre-defined and forced dimensions: Agency and Experience. The four blocks in the experiment are (1) Actor1 in Agency Block, (2) Actor2 in Agency Block, (3) Actor1 in Experience Block, and (4) Actor2 in Experience Block. The order of the blocks is also counter-balanced among the participants so that the blocks with the same agent never follow each other.
Besides the answers of the participants, the response times and the x-y coordinates of the wireless mouse they use while they move toward one of the two response alternatives are recorded. So, the dependent variables are the response and the response time (RT) of the participants, as well as the measurements of maximum deviation (MD) and area under the curve (AUC), derived from the computer mouse-tracking. The variable response is categorical; it can be High or Low, and since the evaluations are done in one of the given blocks, the responses can also be labeled as High-Agency, Low-Agency, High-Experience, or Low-Experience. Response time is a continuous variable; its unit is seconds, and it refers to the elapsed time between the start of the presentation of an action and the occurrence of a mouse click on one of the response alternatives. The MD of a trajectory is a continuous variable, and it refers to the largest perpendicular deviation between the trajectory of the participant(s) and the idealized trajectory (straight line). The AUC of a trajectory is also a continuous variable, and it refers to the geometric area between the trajectory of the participant(s) and the idealized trajectory32.
Stimuli and design of the experiment 
A three-staged experiment is used in the present study. The measurements from the third part are used for the analyses; the first two parts serve as preparation for the final part. Below, we describe each part of the experiment together with the experimental stimuli and hypotheses.
In Experiment Part 1 (lexical training part), the participants complete a training session to understand the concepts of Agency and Experience and the capacity levels represented with the words High and Low. To select the concepts (n = 12) to be used in this training session, some of the authors of the current work conducted a normative study33. Since the present study was planned to be conducted in the native languages of the participants, the concepts were also translated into Turkish before being normalized. Concepts were selected from among those that were strongly associated with the High (n= 3) and Low (n= 3) ends of the two dimensions (six concepts for each). This part is crucial since the participants&#39; understanding of the concepts is expected to guide their evaluation processes.
In Experiment Part 2 (action identification part), participants watch the same eight actions performed by Actor1 and Actor2 one after the other and report what the action is to the experimenter. This section serves as a manipulation check; by presenting all the actions when both actors are performing them, it is possible to make sure that the participants understand the actions and are familiar with the actors before they start the implicit test, where they need to make fast evaluations. The actions selected for Action Class1 and Action Class2 are those that had the highest H scores and confidence levels (four different action exemplars in each action class) according to the results of the two normative studies (N = 219) for each actor condition conducted by some of the authors (manuscript in preparation). All actions are performed within an equal time duration of 6 s.
This is an ongoing study, and it has some other components; however, the hypotheses for the sections described above are as follows: (i) the type of actor will affect the dependent variables; Actor2 will yield longer RTs, higher MDs, and larger AUCs compared to Actor1; (ii) the type of action will affect the dependent measurements; Action Class1 will yield longer RTs, higher MDs, and larger AUCs compared to Action Class2; (iii) the dependent measurements for High and Low responses for the same actor and action class will differ across the block dimensions: Agency and Experience.

Author Spotlight: A Novel Setup to Conduct Naturalistic Laboratory Experiments with Real Human Actors in Scenarios 

A Naturalistic Setup for Presenting Real People and Live Actions in Experimental Psychology and Cognitive Neuroscience Studies

In this study, we introduced a novel setup to conduct naturalistic laboratory experiments, where participants pursue and interact with physically and socially present actors. So, we aim to understand the mechanisms of action perception in real world settings. A significant challenge in experimental research is to design a naturalistic experiment without losing control over the stimuli at the timing.Although there are some tools such as shutter glasses, they do not provide an opportunity to present real and digital stimuli on the same media. Traditionally, visual perception and cognitive neuroscience research study action perception through 2D displays, for example, images or videos. However, actions in the real world are performed by physically present actors, happen here and now, and are actable.Therefore, with this setup, we aim to conduct studies that have high ecological validity. The unique aspect of our setup is a transparent all actor screen to which the participants watch to live actions of a real actor. While the timing of their presentation is precisely controlled, the screen can become opaque and be used as a 2D display when the actor needs to be invisible.We believe that our setup will help psychologists, neuroscientists, and social interaction researchers to reveal fundamental and previously inaccessible cognitive and neural mechanisms of action perception. It'll also help bridge the gap between traditional laboratory experiments, which have a high degree of experimental control, and the studies which conducted in entirely unconstrained and natural settings.

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Perception of others&#39; actions is crucial for survival, interaction, and communication. Despite decades of cognitive neuroscience research dedicated to understanding the perception of actions, we are still far away from developing a neurally inspired computer vision system that approaches human action perception. A major challenge is that actions in the real world consist of temporally unfolding events in space that happen &#34;here and now&#34; and are actable. In contrast, visual perception and cognitive neuroscience research to date have largely studied action perception through 2D displays (e.g., images or videos) that lack the presence of actors in space and time, hence these displays are limited in affording actability. Despite the growing body of knowledge in the field, these challenges must be overcome for a better understanding of the fundamental mechanisms of the perception of others&#39; actions in the real world. The aim of this study is to introduce a novel setup to conduct naturalistic laboratory experiments with live actors in scenarios that approximate real-world settings. The core element of the setup used in this study is a transparent organic light-emitting diode (OLED) screen through which participants can watch the live actions of a physically present actor while the timing of their presentation is precisely controlled. In this work, this setup was tested in a behavioral experiment. We believe that the setup will help researchers reveal fundamental and previously inaccessible cognitive and neural mechanisms of action perception and will be a foundation for future studies investigating social perception and cognition in naturalistic settings.

This study presents a naturalistic experimental setup that allows researchers to present real-time action stimuli, obtain response time and mouse tracking data while participants respond after each stimulus display, and change actors between experimental conditions with a unique system including a special transparent organic light-emitting diode (OLED) screen and light manipulation.

Perception of others&#39; actions is crucial for survival, interaction, and communication. Despite decades of cognitive neuroscience research dedicated to ...