A-2: Explain the philosophical assumptions underlying the science of behavior analysis (e.g., selectionism, determinism, empiricism, parsimony, pragmatism) ©

Target Terms: Determinism, Empiricism, Experimentation, Replication, Parsimony, Philosophical Doubt, Pragmatism, Selectionism 

When we engage in scientific inquiry, we are accepting a set of assumptions about how the world works. Without these shared assumptions, we would not be able to agree on any resulting findings, and it would be impossible to build a body of scientific evidence.

Selectionism (Phylogeny and Ontogeny)

Definition: All life forms naturally and continually evolve through their learning history and evolutionary development. This happens at an individual level, and also on a species level.

Ontogeny: How the environment changes one individual over their lifetime. 

Example in everyday context: An ultra-marathoner may be able to run without stopping for many hours, without any harm to their health. Environmental variables related to exercise behaviors shaped this ability over the person’s lifetime.

Phylogeny: The natural evolution of a species which includes the inheritance of survival characteristics passed down from one generation to the next. 

Example in everyday context: Humans long ago evolves to be bipeds (walk on two legs). The vast majority of human individuals ambulate this way, and prefer walking to other forms of forward movement (such as crawling or slithering). The preference for walking, and physical adaptation to it, was shaped by millions of years of evolution.

Why it matters: Behavioral scientists must take into account how the environment impacts living organisms individually and as a species. The laws of behavior go beyond discrete occurrences of behavior.


Definition: Events that occur in the universe do not happen “out of the blue.” Instead, they occur in an orderly and predictable manner. 

Example in everyday context: It is springtime and the rain showers have begun. The flowers in your garden begin to grow. Rather than thinking the seeds germinated by accident, you should assume that something (the frequent rain and change of seasons) was the catalyst which resulted in vegetation growth. 

Example in clinical context:
A direct support professional working with a client observes them engaging in self-injurious behavior seemingly “out of nowhere.” The direct support professional decides to seek further support from a supervisor, as they do not accept the possibility that self injury could arise for no reason. The supervisor then designs an assessment process to help determine what might be contributing to the self injury.

Example in supervision/consultation context: A teacher requests an observation of a student in their room. He seems eager to work with you and wants to collaborate and receive feedback. When you arrive to begin the process at the appointed time, however, the teacher appears to resist your involvement and does not cooperate, despite your best attempts at building rapport. Puzzled, you consider how to better understand what might be responsible for this change in the teacher’s behavior.

Why it matters: Essentially, determinism means that we assume events are related in systematic ways that can be investigated scientifically. Without determinism guiding scientific practice, it would be impossible to discover functional relations (i.e., cause and effect) between events because we would be happy to accept that things happen for “no reason.”


Definition: Objective observation of events in our environment, using information from (and only from) one or more of our five senses. Empiricism rejects the option of accepting things as truth that are only “known” through channels outside of our five senses (such as mystical powers) or someone “feeling” a certain way and presenting that as evidence for claims outside of their own experience.

Example in everyday context: You are chatting with a friend, who asks you what you feel is the most efficient way to burn calories. Whipping out your best scientific thinking, you reply, “That sounds like an empirical question, because observable evidence can be used to answer it. I wonder what the existing research says about this.” (If your friend’s question had been slightly different – for example, “What is your favorite way of exercising?” – an answer about your opinion would have been perfectly acceptable and not a violate of the principle of empiricism. Opinions are valid as answers when the question was about opinions.)

Example in clinical context:
You are conducting a parent behavioral skills training session with parents of a teenager who engages in severe problem behavior and has been placed in a residential facility. The parents share that they believe their child engages in problem behavior due to “having a condition called Pathological Demand Avoidance.” They want to know if this condition can be cured so that the child can come home. You respectfully listen to their concerns, then explain that your role focuses on developing understanding of variables contributing to problem behavior, developing treatment interventions, and evaluating the effects of treatment in an ongoing manner using objective criteria. In this way, you informed the parents that your practice relies on empiricism.

Example in supervision/consultation context: You are working with a supervisee who is accruing their supervision hours in a school. During supervision, you review a case involving reading instruction. The supervisee says, “I am not sure which instructional strategies I should use to teach this student. Ms Gray said that she likes whole language instruction, and Mr Jones told me that he swears by a reading program that kids use on their tablets.” You help the supervisee develop a strategy to evaluate instructional practices that would be most beneficial for the student’s needs, using empirical methods rather than opinion.

Why it matters: Empiricism requires scientists to draw upon demonstrable phenomena rather than personal opinions. Essentially, empiricism states that knowledge comes from experimentation and experience (hence the term “empirical” used as a way to describe research or classify certain questions – an “empirical question” is one which can be answered using experimentation).


Definition: Requires the manipulation of the independent variable to see the effects on the dependent variable in order to demonstrate a functional relation. 

Example in clinical context:
During therapy sessions at the residential treatment facility, your client perseverates on when their parents are coming to visit. This behavior has become very difficult to redirect using simple verbal statements. You introduce the use of a visual calendar to show your client what day of the week their parent comes to visit. Before you begin your therapy sessions, you start by reviewing the visual calendar with your client. The client does not ask when their parents are coming to visit for the entirety of your session. Then, you remove the visual calendar and the target behavior returns. You then reintroduce it, and the target behavior goes down once more. The introduction of the visual schedule (independent variable) appeared to have an effect on the amount of time the client spends perseverating on their parent visits (dependent variable).  Please see the sections of this site focused on experimental design to learn more about research methods.

Example in supervision/consultation context: A principal works with a consultant to increase first grade teachers’ use of opportunities to respond (OTRs) during their reading block. The intervention (independent variable) is 20 minute behavioral skills training (BST) session, followed by live coaching within the classroom. The behavior targeted for change (dependent variable) is the rate of OTRs during reading. The principal and consultant use a multiple baseline design across participants to demonstrate experimental control and inform the question of whether their intervention was effective. Please see the sections of this site focused on experimental design to learn more about research methods.

Why it matters: Experimentation is the basic strategy behind scientific inquiry. It involves manipulating variables to explore the relationships between them. Experimentation contributes to the knowledge base our work relies on. 

If you’re struggling with dependent versus independent variables, this may help: the INdependent variable is the INtervention.


Definition: The repeating of already-completed experiments in order to determine the reliability and usefulness of findings. We often think of repetition across empirical studies (for example, Dr Doe and colleagues replicate the previously published study conducted by Dr Smith, which was an extension of a study by Dr Jones). That is certainly one form of replication. Conceptually, however, replication is about bringing about a phenomenon more than once under similar conditions. In this sense, we can observe within-session replication within a few minutes, for example, if a client engages in a response every time a particular environmental change occurs. The examples below do not include replication across published studies, as it is the easiest form of replication to understand.

Example in clinical context:
A standard functional analysis is scheduled to be completed with a new patient. The behavior analyst selects forms of aggression (specifically punching and biting) as the target behaviors. They test four conditions: tangible, demand, attention and a control condition. Each condition yields the same results, zero occurrences of the target behavior during the tangible condition, 20-23 occurrences of the target behavior during the demand condition, three to five occurrences of the target behavior during the attention condition and zero occurrences during the control condition. During the demand conditions, in addition to overall high rates of aggression, the aggression also occurred more reliably as a result of work presentation over the course of the session. (In other words, aggression appeared to come under the control of the presentation of work as this pattern was observed multiple times in succession.) Results of the FA suggest that aggression is maintained by escape.

Example in supervision/consultation context: You just started providing consultation to a group home manager. The two of you have agreed that the manager should start by working on implementing effective feedback with their staff members. Last week, you role played in-vivo feedback situations with the manager, and gave your own feedback on their performance in the simulated environment. This week, you observed the manager demonstrating the skills with their staff members with high fidelity. Since you understand the importance of replication, you do not leap to the conclusion that your feedback session last week was solely responsible for this week’s performance. You instead work with the manager to shape other skills, using the same process of role play and feedback, and evaluate the target skills (in other words, you replicate the intervention and take data on the outcomes).

Why it matters: Replication is the primary method which scientists use to determine the reliability and usefulness of their findings, as well as identify mistakes. This is why science is often called a “self-correcting” process. Several repetitions of the same experiment must be done in order for the scientific community to accept the findings into theory and practice. 


Definition: Ruling out all simple, logical explanations before considering more complex or abstract explanations. “The simplest explanation should be the first explanation.”

Example in everyday context: You are walking down the hallway at school and you pass by a friend. You say, “Hello!” The friend continues walking and does not respond. You assume that the friend did not hear you, since this is the simplest explanation. (You would be willing to accept less likely explanations, such as your friend being suddenly mad at you, if you had additional evidence to suggest this.)

Example in clinical context:
A consumer at a group home was recently up all night, disturbing other consumers. Staff assumed that the overnight worker forgot to give the consumer their nighttime medication. The staff nurse at the group home reviewed the consumer’s medication administration record and saw that they received their nighttime medication on time, so this could be ruled out as an explanation as to why they had disrupted sleep. A staff member recalls that night there was a heavy thunderstorm that lasted all night, which may have caused the consumer to have sleep disruption. The group home staff exhibited parsimonious thinking since they ruled out a simple explanation first (the possibility of missing nighttime medication) before they considered a more complex explanation (the loud thunderstorm that occurred during the night). 

Example in supervision/consultation context: You are conducting supervision with your supervisee who is a BCBA ® candidate. During this supervision, you are reviewing the supervisee’s caseload. The supervisee tells you that one of their clients engages in off task behavior after lunch and thinks it is because the client has too much sugar in their lunch, causing them to be more hyperactive. You encourage your supervisee to look for a simpler explanation for the client’s engagement in off task behavior. At your next supervision meeting, the supervisee tells you that they observed their client’s off task behavior after lunch and, after collecting data, determined that the client receives significantly less staff attention in the afternoon. This is a simpler explanation for the off-task behavior, and should have been considered (and possibly ruled out) first. 

Why it matters
: Parsimony helps us guide our reasoning and decision- making processes in a logical and orderly manner, ruling out more likely explanations before exploring more complex possibilities. It helps us to identify reasonable explanations and solutions to the phenomena of interest. 

Philosophical Doubt 

Definition: Continue to question the truth of what is regarded as fact. Exercising philosophical doubt means having a very open, and very critical, mind about everything all the time!

Example in everyday context: Lucy does not generally drink caffeine. When she has been up very late studying, however, she has coffee the next morning before going to work. Lucy therefore only experiences the effects of sleep deprivation and the effects of caffeine together. She understandably misattributes certain effects; for example, she believes that feeling flushed and overly warm (an effect of caffeine for Lucy’s sensitive system) is instead due to being sleep deprived. However, one day she goes out with a friend and has coffee after a great night’s sleep. She is surprised to find that she experiences some of the bodily sensations which she previously thought were the result of sleep deprivation. She adjusts her thinking on the effects of sleep deprivation accordingly. Lucy practiced philosophical doubt by continuing to refine her perception of “the truth” as more information became available to her.

Example in clinical context:
A newly hired behavior analyst reviews a patient’s records, including their functional behavior assessment data, dating back three years from the current date. The results of the functional analysis indicate that aggression toward others served a function of attention. However, interventions have not been successful at reducing aggression. Rather than relying on records that are three years old, the new behavior analyst conducts further assessment to determine if the original assessment still holds true. This new behavior analyst is operating under philosophical doubt, since they are demonstrating a healthy amount of skepticism about the results of a previously conducted functional analysis. 

Example in supervision/consultation context: A veteran behavioral consultant attends a learning seminar which describes a new instructional technique for individuals with multiple disabilities. The presenter claims that this method could be more successful than errorless teaching for certain learners. The behavioral consultant is skeptical, since errorless teaching has a large evidence base and has been practiced for many years. They conduct their own research and find more evidence that supports the new instructional technique under certain situations. The behavioral consultant has exhibited philosophical doubt in this instance, because they demonstrated a healthy amount of skepticism with regard to the new instructional technique, while not completely disregarding it simply because it was novel. 

Why it matters: Science, by definition, cannot be static (unmoving). It is dynamic because we our level of knowledge is constantly expanding. As practitioners, we frequently come into contact with all kinds of claims and information regarding both new and familiar “truths.” Scientists and practitioners need to continually adopt a critical eye when evaluating treatment claims, research results, and so forth. 


Definition: The philosophical attitude that something has value, or is true, to the extent that it leads to successful outcomes when practically applied. (“Truth is an effective action.”)

Example in everyday context: Bryan is interested in improving his general health through diet. He becomes familiar with the broad findings of the empirical research in nutrition, and finds that a diet rich in vegetables and lean protein sources has been linked to health improvements. Bryan changes his diet to be in line with these recommendations. He does not worry about which attributes of the foods he eats are the most impactful to his health, because this information would not further inform his actions. For example, the question of whether tomato seeds are disproportionately responsible for the nutritional value of tomatoes as a whole, while empirically answerable, is completely irrelevant to Bryan. He just eats whole tomatoes and moves on with his life.

Example in clinical context: You have been providing teletherapy via video to a family who need support with managing their children’s behavior. You have taken data on the beneficial effects of your praise on parent cooperation with you recommendations within sessions. When you praise, you always smile, nod, and look directly at the camera. Your supervisor has asked if you think the family is ready to transition to a consultation model where they record themselves implementing the interventions, and you respond with feedback via email. In this situation, a pragmatic consideration would be the extent to which your praise without the smiles, nods, and eye contact would continue to function as reinforcement.

Example in supervision/consultation context: You happen to like wearing blazers, and you always wear some form of blazer at work. You also, of course, make other choices consistent with professionalism. For the past several years, you have been providing consult to a team of community-based mental health workers. Measures of social validity and client outcomes indicate that your consult services are acceptable and valuable to the team and their clients. The question of whether your “business attire” contributes in some way to your success as a professional, while technically something you could investigate empirically, is irrelevant and not a pragmatic concern as long as it would not inform practice.

Why it matters: The science of applied behavior analysis has a focus on improving socially significant behaviors that will impact a person’s life in a positive way. Although there are various types of behaviorism, the practice of applied behavior analysis focuses on both private and public events as environmental variables which contribute to the meaningful analysis and treatment of problems. ABA has value to the extent that it is used effectively to improve peoples’ lives.

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