Rapid visual flicker is known to capture attention. Here we show slow flicker can also capture attention under reciprocal temporal conditions. Observers searched for a target line (vertical or horizontal) among tilted distractors. Distractor lines were surrounded by luminance modulating annuli, all flickering sinusoidally at 1.3 or 12.1 Hz, while the target’s annulus flickered at frequencies within this range. Search times improved with increasing target/distractor frequency differences. For target-distractor frequency separations > 5 Hz reaction times were minimal with (...) high frequency targets correctly identified more rapidly than low frequency targets (~400ms). Critically, however, at these optimal frequency separations search times for low and high frequency targets were unaffected by set size (slow flicker popped out from high flicker, and vice versa), indicating parallel and symmetric search performance when searching for high or low frequency targets. In a ‘cost’ experiment using 1.3 and 12.1 Hz flicker, the unique flickering annulus sometimes surrounded a distractor and, on other trials, surrounded the target. When centred on a distractor, the unique frequency produced a clear and symmetrical search cost. Together, these symmetric pop-out and search costs demonstrate that temporal frequency is a pre-attentive visual feature capable of capturing attention, and that it is relative rather than absolute frequencies that are critical. The shape of the search functions strongly suggest that early visual temporal frequency filters underlie these effects. (shrink)
Some defenders of the principle of alternative possibilities (PAP) have responded to the challenge of Frankfurt-style counterexamples (FSCs) to PAP by arguing that there remains a flicker of freedom -- that is, an alternative possibility for action -- left to the agent in FSCs. I argue that the flicker of freedom strategy is unsuccessful. The strategy requires the supposition that doing an act-on-one''s-own is itself an action of sorts. I argue that either this supposition is confused and leads (...) to counter-intuitive results; or, if the supposition is acceptable, then it is possible to use it to construct a FSC in which there is no flicker of freedom at all. Either way, the flicker of freedom strategy is ineffective against FSCs. Since the flicker of freedom strategy is arguably the best defense of PAP, I conclude that FSCs are successful in showing that PAP is false. An agent can act with moral responsibility without having alternative possibilities available to her. (shrink)
This paper aims to challenge the view that the sign present in many Frankfurt-style scenarios is insufficiently robust to constitute evidence for the possibility of an alternate decision, and therefore inadequate as a means of determining moral responsibility. I have amended Frankfurt’s original scenario, so as to allow Jones, as well as Black, the opportunity to monitor his (Jones’s) own inclination towards a particular decision (the sign). Different outcome possibilities are presented, to the effect that Jones’s awareness of his own (...) inclinations leads to the conclusion that the sign must be either (a) a prior determinate of the decision about to be made, (b) prior and indeterminate (therefore allowing for a contra-inclination decision to be made), or (c) constitutive of a decision that Jones has made but is not yet aware of. In effect, this means that, prior to the intervention of Black, Jones must have decided to do otherwise or could have so decided. Either way, although Frankfurt’s conclusion, that Jones could not have done other than he did, is upheld, the idea that he could not have decided otherwise must be rejected, and with it the view that the sign is nothing more than a flicker of freedom insufficient for assigning morally responsibility. (shrink)
Several recent investigations (Grimes, in press; McConkie and Currie, in preparation) report that large changes in images of natural scenes can remain unnoticed if these are made during saccades. We show here that similar massive effects can be obtained without synchronization to saccades. This is done via a "flicker" technique in which an original and an altered image (each of duration 240 ms) are repetitively alternated, with a blank field (duration 27 or 290 ms) between each display. One of (...) four kinds of change (color, left-right reflection, translation, or appearance/disappearance) were made in the foreground or background of each scene. Many of these changes were difficult to detect, even over long periods of observation (35 seconds). We believe that this is due to the spatially-distributed transient induced by the blank field, which swamps the localized flash that would otherwise draw attention to the changes; observers were therefore forced to rely on higher-level (probably non-iconic) representations of the scenes to detect the change. Our results indicate that the failure to notice scene changes during saccades is not due to saccade-specific mechanisms, but rather, involves more general mechanisms of visual attention. (shrink)
When brief blank fields are placed between alternating displays of an original and a modified scene, a striking form of "change blindness" is induced, where the changes are difficult to see (Rensink, O'Regan, and Clark, 1997). Experiments are presented here examining the dependence of this phenomenon on initial preview and type of transient caused by the blanks. Results support the idea that our representation of the world is a sparse one, coordinated by attentional mechanisms.
The muscles that control the pupil are richly innervated by the autonomic nervous system. While there are central pathways that drive pupil dilations in relation to arousal, there is no anatomical evidence that cortical centers involved with visual selective attention innervate the pupil. In this study, we show that such connections must exist. Specifically, we demonstrate a novel Pupil Frequency Tagging (PFT) method, where oscillatory changes in stimulus brightness over time are mirrored by pupil constrictions and dilations. We find that (...) the luminance induced pupil oscillations are enhanced when covert attention is directed to the flicker stimulus and when targets are correctly detected in an attentional tracking task. These results suggest that the amplitudes of pupil responses closely follow the allocation of focal visual attention and the encoding of stimuli. PFT provides a new opportunity to study top down visual attention itself as well as identifying the pathways and mechanisms that support this unexpected phenomenon. (shrink)
A great deal of attention has been paid recently to the claim that traditional Frankfurt-type counterexamples to the Principle of Alternative Possibilities (PAP), which depend for their success on the presence of a perfectly reliable indicator (or prior sign ) of what an agent will freely do if left to act on his own, are guilty of begging the question against incompatibilists, since such indicators seem to presuppose a deterministic relation between an agent’s free action and its causal antecedents. Objections (...) of this sort have given rise to considerable efforts to construct alternative Frankfurt-type counterexamples that do not rely on prior signs of this kind and so do not presuppose determinism in a way that incompatibilists should find objectionable. One consequence of this shift in the way Frankfurt-type counterexamples are formulated is that it provides an opportunity for the forceful resurgence of certain versions of the so-called flicker defense of PAP. In this paper I develop two versions of the flicker defense, indicate their advantages over other versions of this strategy, and defend them against objections. Insofar as either of these is successful, it will show not only that PAP has yet to be falsified by any of the modified Frankfurt-type counterexamples currently on offer but that cases of this sort are in principle incapable of falsifying PAP. (shrink)
The paper argues that it is possible for an incompatibilist to accept John Martin Fischer’s plausible insistence that the question whether we are morally responsible agents ought not to depend on whether the laws of physics turn out to be deterministic or merely probabilistic. The incompatibilist should do so by rejecting the fundamentalism which entails that the question whether determinism is true is a question merely about the nature of the basic physical laws. It is argued that this is a (...) better option for ensuring the irrelevance of physics than the embrace of semi-compatibilism, since there are reasons for supposing that alternate possibilities are necessary for moral responsibility, despite Fischer’s claims to the contrary. There are two distinct reasons for supposing that alternate possibilities might be necessary for moral responsibility—one of which is to do with fairness, the other to do with agency itself. It is suggested that if one focuses on the second of these reasons, Fischer’s arguments for supposing that alternate possibilities are unnecessary for moral responsibility can be met by the incompatibilist. Some possible reasons for denying that alternate possibilities are necessary for the existence of agency are then raised and rejected. (shrink)
In Otsuka ( 1998 ), I endorse an incompatibilist Principle of Avoidable Blame. In this rejoinder to Fischer and Tognazzini ( 2009 ), I defend this principle against their charge that it is vulnerable to Frankfurt-type counterexample.
One well-known incompatibilist response to Frankfurt-style counterexamples is the ‘flicker-of-freedom strategy’. The flicker strategy claims that even in a Frankfurt-style counterexample, there are still morally relevant alternative possibilities. In the present paper, I differentiate between two distinct understandings of the flicker strategy, as the failure to differentiate these two versions has led some philosophers to argue at cross-purposes. I also explore the respective dialectic roles that the two versions of the flicker strategy play in the debate (...) between compatibilists and incompatibilists. Building on this discussion, I then suggest a reason why the compatibilism/incompatibilism debate has reached a stalemate. (shrink)
Methods. We employed a "flicker" technique, in which an original and a modified image (each of duration 240 ms) continually alternated, with a blank field (duration 80 ms) between each display. Images were all of real-world scenes. One of three kinds of change (appearance/disappearance, color, or translation) was made to an object or region in each scene. Changes were large and easily seen under normal conditions. Subjects viewed the flicker display, and pressed a key when they noticed the (...) change. (shrink)
A striking blindness to changes in real-world scenes can be induced using a variety of techniques (e.g., saccade-, blink-, or flicker-contingent change). The strength and robustness of this phenomenon points towards the involvement of mechanisms central to visual perception. It is proposed here that this induced change blindness can be explained by an..
One of the more powerful impressions created by vision is that of a coherent, richly-detailed world where everything is present simultaneously. Indeed, this impression is so compelling that we tend to ascribe these properties not only to the external world, but to our internal representations as well. But results from several recent experiments argue against this latter ascription. For example, changes in images of real-world scenes often go unnoticed when made during a saccade, flicker, blink, or movie cut. This (...) "change blindness" provides strong evidence against the idea that our brains contain a picture-like representation of the scene that is everywhere detailed and coherent. (shrink)
Large changes in a scene often become difficult to notice if made during an eye movement, image flicker, movie cut, or other such disturbance. It is argued here that this _change blindness_ can serve as a useful tool to explore various aspects of vision. This argument centers around the proposal that focused attention is needed for the explicit perception of change. Given this, the study of change perception can provide a useful way to determine the nature of visual attention, (...) and to cast new light on the way that it is?and is not?involved in visual perception. To illustrate the power of this approach, this paper surveys its use in exploring three different aspects of vision. The first concerns the general nature of _seeing_. To explain why change blindness can be easily induced in experiments but apparently not in everyday life, it is proposed that perception involves a _virtual representation_, where object representations do not accumulate, but are formed as needed. An architecture containing both attentional and nonattentional streams is proposed as a way to implement this scheme. The second aspect concerns the ability of observers to detect change even when they have no visual experience of it. This _sensing_ is found to take on at least two forms: detection without visual experience (but still with conscious awareness), and detection without any awareness at all. It is proposed that these are both due to the operation of a nonattentional visual stream. The final aspect considered is the nature of visual attention itself?the mechanisms involved when _scrutinizing_ items. Experiments using controlled stimuli show the existence of various limits on visual search for change. It is shown that these limits provide a powerful means to map out the attentional mechanisms involved. (shrink)
This thesis is an investigation into free will, and the role of alternative possibilities. I defend an incompatibilist notion of freedom, but argue that such freedom is not exercised in all cases of decision-making. I begin by considering the debate surrounding Harry Frankfurt’s famous argument that alternative possibilities are irrelevant to freedom. I argue that the main disagreement can be best understood by considering the dispute surrounding the 'Flicker-of-Freedom' objection, which contends that there are still alternatives left open (...) in Frankfurt's example. Compatibilists have argued that any such alternatives are outside the agent’s voluntary control and hence irrelevant. But the arguments for this conclusion commit the compatibilist to the more general claim that volitions are not within agents' voluntary control, and incompatibilism is generally motivated by a rejection this claim - so if we could support this claim, we would refute incompatibilism without appealing to Frankfurt’s argument. This disagreement about whether volitions are within agents' voluntary control has not received much attention in recent years, despite figuring implicitly in the debate. But in previous centuries, this figured explicitly as the main focus. I consider the historical debate, started by the famous dispute between Hobbes and Bramhall, and continuing throughout the eighteenth century. Although the libertarian position better captures our ordinary conception of freedom, compatibilists argue that it introduces freedom-undermining irrationality, and randomness of the sort that is either unhelpful or incoherent. Whilst for many cases of decision-making, these challenges are justified, they are not justified in cases involving a particular kind of reasons conflict. I argue that decisions are free in cases of this sort, but we cannot have incompatibilist freedom more generally. However, I also argue that these are the most important cases, given the nature of our concerns about freedom. By restricting the domain of incompatibilist freedom to just these cases, we can avoid introducing irrationality, or randomness of the sort that has made incompatibilism seem incoherent, whilst preserving the incompatibilist's intuition that an important sense of freedom rests on alternative possibilities. (shrink)