This work has noted two countervailing tendencies: the search for information and adaptation to information. The first leads to more conscious access, and the second reduces conscious access: Obviously our model should reflect both. So far, the picture seems quite consistent across the board. Perceptual systems are highly sensitive to information rather than physical energy. Conceptual and goal processes can similarly be viewed as sensitive to information --- to distinctions that make a difference, and that trigger adaptive processes. And there is a special relationship between information and consciousness, as shown by the fact that redundant stimuli fade from consciousness. Note again that in ordinary life, adaptation does not have to be complete: when routine events become partially redundant, other, more informative events demand our attention.               

     In nature, all of an animal's senses work together in active, coherent exploration. Given a surprising noise, a dog's ears will prick up, it will look toward the sound, its pupils dilate, lungs begin sniffing the air, nostrils flare to allow better smelling; the animal will even taste the in-breathed air as it flows over the tongue. If the sound is interesting  the dog will move toward it, constantly sniffing, looking, listening, and licking anything of interest. It is actively searching for information --- for signals that make a difference in the search for food, for social and sexual partners, for dangers to avoid, and often for plain novelty.        

                    In the laboratory, by contrast, we usually examine only one perceptual system at a time; but the same overwhelming preference for information emerges there. There is extensive evidence that eye-movements focus on the most informative parts of a scene. Given a choice between predictable and unpredictable figures, people choose those that are moderately unpredictable: those with enough information to be interesting, but not so much as to be confusing or overwhelming with novelty. And it is well-established that animals and people will work for informative stimulation, without food or any other reward. As we see next, the same restless search for information characterizes conceptual processes, those that are abstract and not directly reducible to perception or imagery.

 In this section we cite evidence that goal contexts define "significant" information; i.e., that people are highly sensitive to signals that reduce uncertainty within goal-defined contexts. Those signals become the objects of attention: we seek to make them conscious. As in the example of a child demanding a new, fascinating toy, this point implies that input  may be repetitive at other levels, but informative in a goal context. We are willing to seek out information that is redundant at the perceptually and conceptually,  as long as it is significant within a dominant goal context. Goals are more important than arbitrary stimuli or concepts; indeed, psychological significance is defined by goals. They  provide the higher-level context of information for any animal. Eating and drinking, avoiding danger and discomfort, competing and cooperating with other animals --- all these activities are defined by goals. In that sense, goal-related input is inherently informative. We can see this in the case of stimulus habituation: when a stimulus signals food to a hungry animal, it can be repeated many times before the orienting response habituates. Conditioning generally  involves reinforcers that tap into biologically significant goals --- food, drink, avoidance of pain, and the like. And classical conditioning is believed to  depend heavily  upon the amount of information given by the conditional stimulus about a significant (goal-related) unconditional stimulus.  It is obvious that people scan the world for significant information, and make it conscious when possible.  Attentional control fades quite quickly in spite of our best efforts, but it can be revived by creating pay-offs for successes and failures; that is, when we create a direct connection between conscious vigilance and a currently significant goal . When there is a monetary reward or penalty, when survival depends upon vigilance --- as in the case of a war-time submarine sonar  operator --- then we can to some extent overcome the tendency of redundant stimuli to fade from consciousness. Thus the claim that goal contexts define significance, and that we actively search for such significance, seems well-supported. This connection is modeled here by showing that we can recruit a goal context to help maintain relevant information on the GW.               

               Summary: Seeking vs. adapting to information.

This work has noted two countervailing tendencies: the search for information and adaptation to information. The first leads to more conscious access, and the second reduces conscious access: Obviously our model should reflect both. So far, the picture seems quite consistent across the board. Perceptual systems are highly sensitive to information rather than physical energy. Conceptual and goal processes can similarly be viewed as sensitive to information --- to distinctions that make a difference, and that trigger adaptive processes. And there is a special relationship between information and consciousness, as shown by the fact that redundant stimuli fade from consciousness.  Note again that in ordinary life, adaptation does not have to be complete: when routine events become partially redundant, other, more informative events demand our attention.  We can now begin to describe this pattern of evidence in terms of GW theory.  difficult to report .  How does the system know what is informative?   How does the GW system determine whether some input is informative? Sometimes we are told that some source of conscious information is important: that is, we accept the goal to pay attention to it. Indeed, that is what we did with the Dalmatian example --- the reader was simply asked to pay attention to the demonstration. Thus sometimes what we make conscious is under the control of goals. However, even when we try to pay attention to a boring and repetitive stimulus, it becomes difficult to do so after a short while. Other thoughts come to mind, and the input fades in spite of our best efforts to pay attention to it. Thus there must be some way in which the system can determine how informative the input is independent of goal-controlled attention.          

                    The most plausible supposition is that the audience decides. Specialized processors that are interested in the global message may feed back their interest, and do so until all the usable information is absorbed, or until some other conscious content becomes more informative. We have previously called this the "Nielsen ratings of the mind," by analogy to the continuous assessment of the popularity of different television programs in the United States.  Presumably we lose conscious access to a repeated stimulus if the receiving processors stop feeding back their interest.  There are indeed feedback loops coming from the cortex and elsewhere to the ERTAS system. It is also consistent with the fact that all neural structures, down to single neurons, habituate in a stimulus-specific way . Specialized processors receive global information, and, as they adapt to it, they no longer respond with feedback requesting more of the global message.                       This is really a kind of  coalition formation between the receiving processors and the processors that support the message. It is as if television sets have feedback monitors that let the broadcasting station know how many people are watching. When the program is popular, the audience supports the input processors --- the actors, writers, and producers of the show. There is a coalition in support of the conscious content. But as the audience adapts to the broadcast, it become predictable and uninformative, so that fewer and fewer audience members continue to watch. The coalition breaks up, and may re-form around another global message.  In summary, conscious experience suggests that the receiving systems are feeding back their interest in the conscious global message. Another way of stating this is to say that any conscious message must be globally informative.            Creating a coalition of global senders and receivers presumably takes time. A short tentative global message may first be broadcast. Some receivers may request more of it, resulting in a longer message, which gathers more support, and so on, in a "snowballing" fashion, until finally the global message becomes available long enough to report as a conscious event . We have  previously referred to this notion as the Momentary Access hypothesis. It is consistent with Libet's  finding that skin stimulation of moderate intensity may take as long as .5 seconds to become conscious, even though cortical activity from the stimulus can be recorded long before that time.              

When one conscious event becomes redundant, the next  most informative input becomes conscious.              

                    The model does not imply that all conscious events are completely adapted to until they are utterly redundant. Most of the time when we read or hear a sentence we do not wait for complete adaptation to take place --- we only need to adapt to a single aspect of the input. The reader of this book is not going to repeat each word or sentence over and over again to the point of semantic satiation --- it is enough to simply wait for the "click of comprehension." Instead, the model suggests there is relative adaptation: We adapt to a conscious event to some point, perhaps until we feel that we have comprehended it. After that, other potential conscious contents may be scanned, to see if there is one with greater significance, or with greater ability to recruit a coalition of receivers to support its dominance.

      Informativeness and objectification, redundancy and  contextualization.                              

                    We have suggested that during the information stage of adaptation, there are choices in the stimulus, either implicit or explicit. To see even a simple black line on white paper means that there is an implicit figure-ground comparison; the brightness of the line and paper are implicitly compared to previous visual intensities, as well as to adjacent contrasting areas; and so on. There is no conscious content without implicit comparison. This point has an interesting bearing on the general issue of contextualization vs. objectification. Conscious contents seem always to be  object-like. Even abstract entities and processes tend to be reified and treated as objects --- we speak of "mathematics," "democracy," and "process," as if they are objects  like chairs, tables, and pencils. Of course when these ideas become thoroughly predictable, they become habituated and automatic, and fade from consciousness, though even then they can constrain future conscious experience. That is to say, they have become context, by definition of that term. We can call this process contextualization. The reverse occurs in the case of violated presuppositions discussed above. Presupposed contextual constraints can become conscious when they are violated, and hence they become object-like (decontextualized). They are taken From the status of context and objectified --- turned into  object of experience and thought. The notions of contextualization and objectification have wide-ranging consequences.                 

               When repeated experiences do not fade: Is informativeness a 

                               necessary  condition for conscious experience?                           

The claim that informativeness is necessary for a conscious event depends heavily upon the Redundancy Effects discussed above --- those cases where input is repeated over and over again and consequently disappears from consciousness. These effects are pervasive: they exist in all senses, in mental imagery, in motor skills, and apparently in  conceptual processes as well. However, if there are clear exceptions to the Redundancy Effects, the hypothesis of a necessary connection between consciousness and information cannot be maintained. The existence of genuine counter-examples would destroy the "necessary condition" claim. In this section we discuss some apparent counter-examples and show that these can generally be handled in a broad information- theoretic framework. The "necessary condition" claim, we conclude, seems quite defensible.       '           

               The apparent implausibility of Redundancy Effects in      

                                  everyday life.                              

On the face of it there is something implausible about the idea that fall conscious experiences fade when they become automatically predictable. If that were true, how could we experience the same road to work every day of our lives? Or the same kitchen table, the same bedroom, the same faces of friends and family? Is there a prima facie‹ absurdity in the informativeness claim? Some Redundancy Effects, like the stopped retinal images discussed above, occur only under laboratory conditions. Perhaps the laboratory creates artificial circumstances that do not represent the underlying reality?  Some of the counterexamples pose genuine challenges, and others do not. For instance, Neisser trained people to search for a single word in a list of words, or a face in a photograph of a crowd. People can learn to do this very well, so that the target face seems to "pop out" of the crowd quite automatically.  What becomes automatic in the Neisser studies is the act of attending, the act of making things conscious, as opposed to the object that becomes conscious. The particular face in the crowd, or the fact that this face is to be found in this particular place, is quite new and informative. If this is true, the act of attending should fade from  consciousness even if the target does not, and the Neisser studies do not provide a true counter-argument to the claim that repeated conscious contents fade with redundancy.         

                    Some other counterarguments are more difficult to handle.  There are in fact clear cases where habituation of awareness does not hold, where  we continue to be conscious of repeated experiences. Pavlov observed "spontaneous dishabituation" among dogs exposed to repeated sounds, and such things as chronic pain never permanently fade from the consciousness of its victims. Even stopped retinal images do not fade permanently; they tend to reappear in a transformed way, so that the word "BEER" will fade and reappear as "PEER," "PEEP," "REFP," etc. These cases may represent true counter-examples. We will argue below that we can retain the informativeness hypothesis in spite of these counterarguments, if we take into account the fact that repeated material can remain informative if its context of interpretation changes‹. This is true of the formal definition of information , which permits a repeated message to continue to yield information if the context of choices within which the signal is received is altered. Information is a matter of the relationship of a message to its context, not of either message or context alone. Thus, in cases where a repeated event does not fade, we can ask whether its context of interpretation has changed.

 Consciousness to repeated events is not lost in the following cases:                             

                    (1) Variability. The event seems to be repeated, but in fact there is variability in the input. Visual information provides a good example. We would expect that looking at a clock would cause the stimulus to fade from consciousness if the informativeness hypothesis is correct. In fact, the clock seems to stay in consciousness; but of course, this is only because we cannot control involuntary eye movements, especially physiological nystagmus. We only seem to be staring fixedly at the clock --- in fact, the input is variable.  Similarly, automaticity of skill learning does not occur if the skill is in fact variable.             

                    (2) Learning.  Fading does not occur if the repeated stimulus is incompletely learned, so that it is better understood with each repetition, and hence has not become truly redundant. This is of course the classical learning curve, the relationship between practice and learning which is so much better known than the equally common Redundancy Effects.          

                    (3) Relative adaptation. Fading does not occur if we do not repeat the event to the point of complete adaptation. We stay conscious of an event if we move on to another one as soon as enough adaptation has occurred. We try to listen to a repeating owrd, but in fact, a thought, a feeling, or an image begins to come to mind, even before the target stimulus fades. Most of the time we are satisfied with relative adaptation, as noted above.               

                    (4) Ambiguity. Redundancy does not occur as quickly if the stimulus is ambiguous and can be reinterpreted, so that it isconsciously experienced to be different.  We have already discussed the prevalence of ambiguity in the world. Language is rife with ambiguity; the social world is profoundly ambiguous; the future is unknown and ambiguous; bodily arousal can often  be interpreted in more than one way; conceptual ambiguity is prevalent, even in science.          

                    Good naturalistic examples of spontaneous reinterpretation of ambiguous events can be found in art, literature, music, mathematics and science. Any piece of polyphonic music shows figure-ground ambiguity. If we pay attention to one melodic line, the others will fade into the "ground" of our perceptual experience. In this sense all polyphonic music can be experienced in many different ways. Further, even a single melodic line can be reinterpreted, because we are continually generating expectations about the next few notes before we hear them; if the composer is clever he will occasionally surprise us with an unexpected melodic turn. Truly great composers continually surprise and please us by the interplay of the predictable and unpredictable in the fate of an ongoing melody.          

                    Musicians often find new and different sources of pleasure in the same composition, even when it is played hundreds of times over a period of years. Rather than fading from consciousness, the music is continually reinterpreted.  This is true for other art forms as well. Serious works of art cannot be understood completely on first exposure. They require a many-leveled process of reinterpretation before we fully appreciate them. Reinterpretation can happen spontaneously, simply by allowing oneself to be conscious of the work, or under guided voluntary control.         

                    (5) Significance and purpose can keep repeated information in awareness. Fading does not occur even with a repeated stimulus if it has significance beyond itself which has not been adapted to. Redundancy may be avoided if there is an ongoing Œgoal‹ in attending to the repeated stimulus, especially if the observer receives feedback on the success or failure of his goal.

Presumably the more important the goal, the more we resist redundancy, because the stimulus, which may be redundant perceptually, conveys deep significance.               

                    Suppose two people are driving in a car to a new destination, but only the driver is involved in finding the way --- the passenger is just enjoying the ride. When they go to the same place a week later, which one is likely to remember the way better? Common observation suggests that the driver will, even if the passenger experienced the same physical flow of stimulation. The difference is that the driver engaged the world in a purposeful way, wondering whether to turn here or there, noting distinctive landmarks at critical choice-points, and the like. The driver's conscious experience was guided by a set of purposes, while the passenger's experience was relatively purposeless.              

                    If people have different experiences of a single event when they are guided by different purposes, their memories should also be different. Thus Pichert and Anderson  presented the same story about two boys playing in a house to two groups of subjects. The first group was told to take the perspective of a home buyer, while the second group assumed the viewpoint of a burglar "casing" the house. Different facts were recalled by the two groups. The "home buyers" were more likely to remember a leaking roof, while the "burglars" were more likely to remember the location of the color television . This is consistent with the view that different purposes yield different experiences --- or, as we will argue below, inner contextual changes can create new experiences of the same event.         

                    One effect of purpose is voluntary release from habituation --c one aspect of voluntary attention. We can voluntarily make unconscious habituated stimuli conscious again. Simply by choosing to pay attention, the reader can again become conscious of the feeling of the chair, of the background noise, of the quality of the ambient light, and even of semantic presuppositions. We will not model this volitional phenomenon until  , where we discuss voluntary attention. Note however that attempts at voluntary control shift the internal context of the signal. Thus this example seems to fit the claim  that an internal shift of context can take place even if the physical input is repetitive, resulting in a new conscious experience.          

                    (6) Contextual shifts. Repetition sometimes leads to spontaneous perceptual transformations. When we listen passively to a repeated word, we soon begin hearing different words. Within a minute or so a word like "break" will be begin to be heard as "rake, wake, wait, rape, ape, ate, ache, ..." etc. This remarkable Verbal Transformation Effect is different from semantic satiation (described above) because here the subject is not saying the word, but merely listening to it.   

                    A very similar phenomenon is observed with stopped retinal images. In this case the transformations change according to the visual properties of letters rather than following phonemic or sound patterns .  Thus BEER will turn to BEEP, because the P and R are visually similar, while in the auditory case "break" may change to "wake" because the /r/ and /w/ are  phonetically similar.  Because our knowledge of the acoustic properties of speech has improved dramatically over the past twenty years, it has been possible to examine the Verbal Transformation process in detail. It is well-established that sounds like /ba/ and /pa/ differ in only one articulatory property. In /ba/ the vocal chords begin to vibrate a few tens of milliseconds before the lips open, while in the case of /pa/ the lips open a short time before the start of voicing. Using computer generated speech one can systematically vary the "voice onset time" (the time difference between voicing and opening the lips), and locate the exact boundary between the perceived /pa/ and /ba/. Now we can examine the effects of selective habituation. If /pa/ is repeated over and over again, the boundary will shift in the direction of opening before voicing; if /ba/ is repeated over and over again, the reverse occurs. This effect has been shown with natural as well as computer-generated speech.  The implication is that if one day we heard all /p/'s and no /b/'s, our perception of these sounds would be grossly distorted, because the phonetic boundaries would shift. But the distortion would go in the right direction. If we heard all /p/'s, the /b/ category would expand, so that more and more cases would be interpreted as /b/'s. Thus the phonetic system acts to regulate itself, and to maintain a relatively constant number of /b/'s and /p/'s. In addition, the actual frequency of these "opponent" phonemes in the language is roughly the same ccc we normally hear rougly equal numbers of /b/'s and /p/'s ccc  so that the boundary stays at the same voice-onset time.    Thus the context of the information can vary, but the system is designed to keep it reasonably stable under most circumstances. Generally speaking, the stability of our perceptual contexts depend upon the existence of variation in the perceptual contents. The function of the distribution of /p/'s and /b/'s in a language may be to create enough variability to maintain the categorical boundary. This is similar to the case of physiological nystagmus, the function of which may be to avoid excessive redundancy of input. A similar argument also applies to opponent processes in other senses, such as color perception.  Thus context can change, especially if we are exposed to only one end of a continuum of variation.        
                    This conclusion also comes from the Adaptation Level (AL) Theory of Helson (Helson, 1964). Our ability to specify the "expected"  stimulus value in perception  or judgment depends largely on our experience of the extremes in the same dimension. We will judge criminality with less severity if we are routinely exposed to rapes and murders (if only on television). As a result, our judgment of criminal severity changes. Political radicalization may work through the same mechanism; the more we become used to an extreme belief, the less extreme it seems. Again, our experience of an event depends upon our previous related experiences, even though these are not conscious at the time. Again, the context changes when we are exposed repeatedly to one end of the continuum of variation.        

                    Now we can go back to our original question. Why are there cases of repetition that do not result in conscious fading? One plausible suggestion is that the context has changed. When the same word is repeated over and over again, or when someone is exposed to a stopped retinal image of a word, we observe fading, but also transformation. The fading can be explained as a Redundancy Effect, but existence of transformations requires another explanation. The hypothesis is that as one extreme value of an opponent process is repeated over and over again, the context of interpretation shifts. This is clearly the case for Verbal Transformation, and it is at least plausible for the stopped retinal images in the visual system.  Of course the same physical signal in a different context creates different information. In this way we can provide a satisfying account for these interesting counter-arguments to the informativeness hypothesis. In sum: Repeated signals may not fade from consciousness if they are incompletely known, so that each repetition allows more information to be absorbed; if the signals  are variable; if they are ambiguous, so that they can be interpreted in different ways; if they serve a larger purpose which is not redundant;  or if the context drifts, so that the same signal remains informative.  It seems therefore as if we can explain the apparent counterarguments to the "informativeness criterion" for conscious experience. Of course this question deserves much more testing.

We have suggested that all conscious experience must be informative --- that true redundancy leads to a loss of consciousness of a message. The evidence for this is quite pervasive, ranging from repeated stimuli in all sensory modalities, to repeated visual images, automatized skills, semantic satiation, and even stable conceptual presuppositions.  There are counter-arguments which seem compelling at first, but which are less so upon further examination. Although more research is needed on these questions, the position that informativeness is a necessary condition for conscious experience seems to be quite defensible.

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