The ability to recognize and respond based on the relational qualities of objects regardless of absolute attributes that each one possesses is named relational behavior. From an ecological view, relational behavior could be critical to the adjustment of the organisms, humans and not humans, to complex and dynamic natural environments. In social and ecological contexts, the organisms are constrained to respond to permutable aspects of the environment (e.g., food, predators) that vary in relation to given qualities (e.g., size, color, smell, the intensity of a given sound, etc.) of the objects, events, and other organisms. One of the most exciting and controversial issues in the history of behavioral science is the emergence of relational behavior. This is, do animals (non-humans and humans) perceive and respond to relational qualities of stimuli, regardless of the absolute attributes that each one possess?1,2,3,4,5. The affirmative answer implies that organisms' responses integrates segments of stimulation that vary in degree in, at least, one relevant dimension or quality, such as the size or saturation of the stimuli6,7. In spite of the cited controversy, there is strong evidence that supports the emergence of relational behavior in animals4,8,9,10 and humans11,12,13,14,15,16,17,18.
Different paradigms have been used for the analysis of relational behavior. The most extensively employed has been the transposition task5,8. In the transposition task, the participant responds to a given stimulus in such a way that its relevant property (e.g., 'shorter than') is relative to the property of other stimuli in the context of a composed gradient of multiple values (at least three) in a given dimension (e.g., size). Different specific values of the stimuli can take different relational values within the gradient; this is, the specific value of each stimulus can permute its relational values in a given dimension. In simple words, the same stimuli could be 'shorter than' or 'bigger than' depending on comparison stimuli within a size gradient. Some of the reasons of why the transposition task has been a central paradigm for the study of relational behavior are the following: a) the paradigm is susceptible to be extended to different stimuli dimensions2,19,20,21,22,23,24,25; b) by consequence, it is useful for the study of relational behavior in different species (e.g., chickens, pigeons, chimpanzee, turtles, horses, humans)2,4,10,11,18,26; c) it clearly shows changes of the relational value of the stimuli9; d) the task allows parametrical variations of different relevant factors involved in relational behaviour9 and; e) the task allows to conduct comparative studies between different stimuli dimensions and different species or organisms27,28,29,30.
The study of relational behavior in animals is more extensive, systematic and has stronger evidence than in humans. The main reason of this is the 'ceiling effect' frequently observed when the participants are humans11. In this context, recently challenging tasks have been proposed based on transposition for the study of relational behavior in this population6,7,11. In this way, the present work advances from the previous ones and presents a paradigm based on a modified-transposition task for the continuous analysis of relational behavior in humans.
Relational behavior under the transposition paradigm has been usually studied in simple choice situations, with only two stimulus options, and a reduced number of values along a single stimulus dimension in which participants are not allowed to display active patterns with respect to stimuli (e.g., inspecting, dragging, moving, and placing figures). Nevertheless, the experimental analysis of relational behavior might include situations with a) a greater number of stimulus values that allows to permutate or change the relational value of the stimuli; b) more than one relevant stimulus dimension and c) active behavioral patterns requirements, beyond the usually discrete dichotomous selections of the participants. These modifications would allow to evaluate factors not previously considered, mainly, the role of active patterns (e.g., inspecting, dragging, moving and placing figures) in relational behavior, and might prevent the "ceiling effect" observed when linguistic humans solve the standard task11.
RBDT allows the integration of patterns based on discrete responses (e.g., stimuli selection, placement of figures) and continuous responses (e.g., tracking of cursor movements, figure dragging) to analyze the emergence of relational behavior. Two different relational compounds, comprising two stimulus each one, show the same relational properties. They are presented as a sample to compose two new stimulus segments, by means of the active patterns of the participant. The task requires the relational comparability of the stimulus segments. This involves that each one of the two constructed stimulus-segments can be compared to one another as equivalent in terms of their relational properties, but also with respect to the two-sample stimulus-segments. The relations are identified in terms of "greater than" or "less than" magnitude (i.e., size or saturation).
To exemplify some of the possibilities of the experimental arrangements allowed by the presented paradigm, two experiments were conducted. The first experiment shows an exploration of relational behavior under different relational criteria without restriction of active patterns of behavior. The second experiment contrasts the dynamics of relational behavior under restriction of behavioral patterns adding a continuous recording and analysis of dragging and inspection activity with the mouse cursor.