Reading M9 – A strange thought experiment


Reading M9 – A strange thought experiment

In the category of strange things behavior analysts wonder about when they have nothing better to do is this question: What would happen if an individual had no sensory capabilities at all? You might be forgiven for not being able to immediately imagine such a case, and the behavioral ramifications should certainly give you pause. Perhaps you’ve thought about how you would go about teaching a Helen Keller child, but this hypothetical goes way beyond the limitations of being blind and deaf. Assuming the customary five senses, there are two approaches to answering the question.

Being born without sensory capabilities

What if a baby was born without having the senses of vision, hearing, smell, taste, and touch? In order to focus on the heart of the question, we should assume that the baby’s brain functions were otherwise normal, although from a neurological perspective, this would probably be a difficult assumption to support. The reason for stipulating that the baby’s brain otherwise worked as it normally would is to avoid consideration of any other reasons that it would have difficulty learning. Of course, we know that the lack of environmental stimulation would soon lead to accumulating impairments in brain development, but that is beside the point here.

The most profound and pervasive outcome of a baby being born without any sensory capabilities is that it would have great difficulty learning from experience. As we know, behavior develops largely because of its consequences in specific environmental contexts.  Without any sensory capabilities, these consequences would have no effects. Environmental events that we would normally call stimuli would not function as such because they would not have the effects stimuli usually have – they would not stimulate. As a result, they would have no impact on the behaviors that produced them. Not only would the consequences of responses (perhaps more accurately called “actions” or “movements” in this context) not influence behavior, they would not create the usual contextual control by environmental stimuli that makes behavior functional.

For example, a baby learns to hold its bottle because certain movements guided by visual and tactile stimuli are followed by certain consequences (the visual and tactile sensations of the bottle and nipple, as well as the taste of milk).  In this scenario, these consequences would not have any effect, nor would the contextual stimuli come to exert control over responding. It’s hard to understand how the baby would acquire this behavior. It’s not just that it couldn’t see the bottle, it wouldn’t be able to locate it by touch either, nor be guided by any auditory feedback that might be arranged. And if the bottle were simply placed in its mouth, it would not detect it or taste the milk.

In other words, the biggest problem would be the absence of sources of positive reinforcement and the means of extending its effects on behavior to environmental stimuli that would make emerging behaviors occur at the right time.  Although the sensation of a full stomach might function as a reinforcer, it would be too delayed for training purposes.  There are other possible sources of reinforcement that might be used to build a limited relationship with the environment, such as internal sensations like acceleration/deceleration, but they would be difficult to use in practical ways.  Even if we had an adequate reinforcer, it would be paired with environmental stimuli that could not be sensed, and any learned responding would presumably not reliably occur under the right conditions.

In sum, it would be quite difficult for the baby to learn anything, so it would require complete and continuous care.  If this care was successful, the baby might survive reasonably well, but it would be difficult to teach even rudimentary skills.  In other words, it would be profoundly intellectually disabled, though not because of the kind of brain malfunctions we usually associate with this diagnosis.

Losing sensory capabilities as an adult

If we imagine that an otherwise normal adult was to suddenly lose all sensory capabilities while otherwise retaining normal brain functions, the person would be left with a full repertoire but enormous constraints on exercising it, and all previously learned skills would gradually deteriorate.  The most serious problems wouldn’t come from losing smell and taste, which are not uncommon sensory deficits. With the benefit of a fully developed repertoire, even losing sight and hearing could be accommodated, though the psychological effects of suddenly being cut off from all four of these senses are hard to imagine.

Losing the sense of touch, however, given the lack of sight and hearing would be pretty serious.  The person would be like Helen Keller, but without the ability to deal with the environment by touch.  As we know, this was her salvation, and it would have been very difficult for her to learn without it. From a practical perspective, taste and smell are simply less useful ways of interfacing with the environment. This unfortunate person would have the benefit of having already learned what Helen Keller had to struggle for, but a repertoire needs unceasing maintenance to continue its usefulness. With this complete sensory loss, adaptive adjustments in the person’s behavior (both moment-to-moment as well as long term) would pretty much no longer be possible, which would quickly render the repertoire useless. It is difficult to imagine what it would be like for an adult repertoire to suddenly lose its “hand-in-glove” relationship with the environment, but this would be the result of living in a sensory void.

As if this isn’t enough, one of the difficulties of being blind is that you can’t see what you’re about to come into contact with, and it’s easy to get hurt.  Without a sense of touch, however, there would be no way to avoid injury using tactile feedback, which means the ability to move around would be greatly restricted, and the person would require a special environment and continuous, comprehensive care.  Even behaviors such as self-feeding would be difficult – how could a person get food to his or her mouth and know when it arrived and should be chewed and swallowed?  Proprioceptive feedback from movement would only help so much.  These disadvantages of not being able to see or experience touch could be ameliorated if hearing was possible, but that’s not part of this exercise.

Although this hypothetical adult could talk, having previously learned this skill, he or she would not know if anyone was listening or even present, and others could not communicate with the person in return.  The psychological effects of these limitations would vary from one person to another, but it’s hard to imagine they wouldn’t be devastating.  Nothing would be specifically pleasurable or aversive, aside from internal sensations, which would immediately become very important to the individual. It would be understandable if the person didn’t soon wonder whether life was still worth living.


This rather strange thought experiment emphasizes two observations that might be old news to behavior analysts, but less obvious to others. First, there isn’t much to human nature without learning, and not just what it takes to develop an adult repertoire, but what it takes to maintain one. Behavior analysts have always appreciated the gravity of this fact, although most people – encouraged by convictions about the magical role of mental “phenomena” – have only a vague appreciation of the contribution of learning. Second, learning requires a working interface between the organism and the environment. Behavior is that interface, but its adaptive viability requires sensations. We can manage with some sensory deficits, often not too badly at all, but it doesn’t seem that life without all five classic senses would be much of a life as we know it.