Testing qualifications: a worry about sufficiency

Suppose that your partner decides to surprise you by fixing up your apartment while you are away. When you get back, you register all sorts of inconsistencies with how you expected your place to look. The couch in the living room looks lighter, artwork is rearranged, and furniture has been moved. According to the Mismatch Model, we see absences of objects when we detect mismatches about those objects. So, is it right to conclude that you will see an absence whenever there is a discrepancy between your memory of the apartment and its new looks?

Suppose we answer in the affirmative. We could simply accept that seeing absence is more widespread than we originally thought. The result is a very liberal account of absence perception: every time you detect a mismatch, you see an absence. Is this consequence problematic? I believe so. Our basic intuition seems to be that we can see differences without seeing absences. For example, you may notice that your favorite couch got reupholstered, or that things scattered around your desk look different, without taking anything to be absent or replaced. The point generalizes. Our expectations

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are constantly frustrated when we interact with the world, and the resultant disconfirmation responses have been explained by the mismatch detection. But it seems unreasonable to think that every

violated expectation – and the associated mismatch – must elicit an experience of the absence of an object. Many mismatches only generate perceptions of changes in objects or in spaces that they occupy.

Thus, the above account of absence perception is too liberal; one may mismatch and not see an absence. What follows? If seeing absence relies on the same mechanism of mismatch as certain paradigms of positive seeing (those involving expectancy violations), then mismatches cannot demarcate seeing absence from positive seeing. The proponent of CA can quickly turn this result in her favor. If the Mismatch Model is incomplete, then we are under pressure to look for another representational vehicle of absence perception in order to complete it. Seeing absence will be in trouble if this new ingredient turns out to be cognitive.

The force of the objection, then, is not just that the Mismatch Model fails to give us a complete picture of what goes on in experiences of absence. It is that the completed model may fail to validate these experiences as genuine states of seeing. I think, however, that the search for the new ingredients of experiences of perception is unnecessary, and that the objection can be defused by introducing qualifications on mismatches instead of adding new vehicles to mismatches. The basic shape of my response will be that mismatches of the appropriate type are sufficient to account for seeing absence. In fact, no new qualifications on mismatches are necessary; we only need to unpack the restrictions introduced earlier.

First, note that the Mismatch Model restricts absence mismatches to those occurring at the object-level. This removes some of the bite from the objection. When you enter the remodeled apartment, your visual system will rapidly pick up on changed features in the apartment and will update scene representations. Many of these mismatches will be too low-level to constitute experiences of absence. But what about the mismatches at the right level? To elaborate on the example, suppose that you are nearing home and you can’t wait to crash on your favorite red couch.

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You enter your apartment and see a gray couch instead. Two reactions are possible. You may experience absence of your old couch and get upset, or you may hop on your couch noting its new cover. Both reactions involve object-level mismatches, so in virtue of what do they add up to different experiences?

There is an intuitive way to respond to the objection. Seeing a gray couch cues you that your old couch is gone because it does not occur to you that your couch could be reupholstered. A different set of expectations (knowing about the reupholstering) or a different sort of change (stains on the couch) would not result in an experience of absence. To generalize: S experiences absence of an object instead of a mere change in an object when S takes the detected cues to be incompatible with persistence of that object.

There are two worries about this response. First, aren’t there counterexamples? Couldn’t there be cases when one notices change in an object incompatible with its persistence conditions, and not experience its absence? Conversely, couldn’t one notice change in an object consistent with its persistence conditions and still experience its absence? Second, bracketing the counterexamples, doesn’t this response make my account of seeing absence cognitive?

Beginning with the first set of questions, such cases are certainly possible but they do not undermine the proposal. Mismatches signal absences by virtue of their interaction with the subject’s expectational set. Success of this process is dependent on a variety of factors. For instance, if you care about your couch, you will be disposed to see the change you notice in its location. Moreover, the absence of your couch will be hard to miss if you see an empty spot in its place. But there are cases when analysis of a mismatch is flawed or gets interrupted. If you encounter a fascinating new object in place of your couch (such as a giant fish tank), or if you look only briefly at where your couch used to stand, you may bypass an experience of absence and only see difference.

In sum, our expectations are constantly frustrated when we interact with the world, but it seems implausible that every mismatch underlying a violation of expectation indicates an absence. What’s the solution? Intuitively, we experience absences of objects when we take the detected cues to be

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incompatible with persistence of those objects. In our case, the cue – the mismatch between red and blue – indicates an absence because it is not a part of your (current) expectation set that your couch could be reupholstered. Processes like visual search or observation of a deviant pattern will set the relevant expectations and thus determine the interpretation of a mismatch.

One might worry that these qualifications are not enough. Isn’t it possible to engage the appropriate expectations, token an object-level mismatch, yet not see an absence? It is possible. Analysis of mismatches can be interrupted or helped by various factors, and salience of an object, tasks, and properties of the visual scene have impact on absence-seeing just as they do onpositive seeing. Given that such factors affect the analysis of mismatches, should we incorporate them into the Mismatch Model to block the overgeneralization concern? Doing this would misjudge the nature of the current project. I set out to characterize paradigmatic cases where seeing absence does occur. These cases involve object-level mismatches whose semantic uptake is a function of the tasks they are embedded in and the expectations engaged by those tasks. Settling when or how frequently these conditions are met is beyond the scope of my project.

In sum, the Mismatch Model tells us what vehicles are constitutive of experiences of absence. It is not an account of their likely causes. While it is worth exploring whether mismatches and the associated experiences of absence can be generated without their typical causes (without expecting to see the object or its absence), the Mismatch Model does not have to take a stand on this issue. With these qualifications in hand, we are ready to formulate the final proposal about seeing absence.

The Mismatch Model (MM)

Visual experience of absence of an object consists in an object-level mismatch between a template of that object held in visual working memory and a percept of the observed stimulus.