Arien Mack

An investigation of the relationship between eye and retinal image movement in the perception of movement

The question investigated was whether or not eye movements accompanied by abnormal retinal image movements, movements that are either or both at a different rate or in a different direction than the eye movement, predictably lead to perceived movement. Os reported whether or not they saw a visual target move when the movement of the target was either dependent on and simultaneous with their eye movements or when the target movement was independent of their eye movements. In the main experiment, observations were made when the ratio between eye and target movement fem/tm) was 2/5, 1/5, 1/10, 1/20, and 0. All these ratios were tested when the direction of the target movement was in the same (H+), opposite (H−), and at right angles to (V+, V−) the movement of the eyes. Eye movements, target movements, and reports of target movement were recorded. Results indicate that a discrepancy between eye and target movement greater than 20% predictably leads to perceived target movement, whereas a discrepancy of 5% or less rarely leads to perceived movement. The results are interpreted as support for the operation of a compensatory mechanism during eye movements.

Perceptual organization and attention

It is widely assumed that the grouping of the visual field first described by the Gestalt psychologists and the related phenomenon of texture segregation occur very early in the processing of visual information and involve preattentive processes. All the recent evidence supporting this assumption comes from visual search experiments in which the subject is actively looking for a target and attending to the stimulus. The question at issue is whether these kinds of patterns are perceived under conditions of inattention, i.e., when observers are not searching for them. We performed six experiments to determine whether texture segregation and grouping by similarity or proximity are perceived under conditions of inattention. On the first two trials subjects were asked to report the longer arm of a briefly presented cross which was surrounded by a pattern of ungrouped small elements. On the third trial and subsequent control trials these elements were configured into grouping patterns and subjects queried about them immediately following their line length reports. The results establish that neither texture segregation nor grouping by similarity of lightness or proximity are perceived under conditions of inattention. They support the conclusion that there is an earlier stage of processing than that referred to as preattentive.

Perception without attention: Results of a new method ☆

Having found by the use of a new method for examining perception without attention that grouping and texture segregation do not seem to occur (see Mack, Tang, Tuma, Kahn, & Rock (1992) Cognitive Psychology, 24, we go on to ask what is perceived without attention using this new method. Our subjects receive only one inattention trial in a sequence of trials involving a visual distraction task. In addition to the distraction task in the inattention trial, subjects received a stimulus of which they had no prior knowledge or expectation and were questioned or tested directly afterward for their perception of that stimulus. Two subsequent trials containing test stimuli serve as within-subject controls. The results of a series of experiments indicate that the presence of one or more stimulus objects and their locations are preattentively perceived, as is their color, but shape is not. Because individual items are detected without attention, we conclude that perceptual organization is initially based on a principle in which connected regions of uniform stimulation are inferred to be discrete units (the principle of uniform connectedness). One striking, unexpected finding is that without attention many subjects have no awareness at all of the stimulus object, an effect we call inattentional blindness.

Saccadic programming and perceived location.

The retinal location of a saccadic target was made discrepant with its perceived position by means of an induced displacement. If localizing the target required information stored in memory, the eye was directed to the perceived target position. Otherwise, it was directed to its retinal location. These findings do not conform to either a strictly retinotopic or spatiotopic model of oculomotor control. Rather they suggest that the position information used to program saccades may be either perceptual or retinal/spatial depending upon whether the information must be accessed from memory.

The loss of position constancy during pursuit eye movements.

There is no question that there is some toss of position constancy associated with smooth eye movements. Stationary objects whose images are caused to move across the retina by these eye movements frequently occasion the perception of object motion. This phenomenon. first commented on by Filehne. has been referred to as the Filehne illusion f1922). Whife there is no generahy accepted explanation of it. it has been taken as evidence that, unfike saccadic eye movements. smooth eye movements do not generate information which can serve as compensatory perceptual function (Dodge. 1904: Stoper, 1967. 1973). This view only makes sense. however. if the constancy toss during smooth eye movements is complete. For a less than comptete ioss suggests that, at feast to some extent, image dispfacements are compensated for by smooth eye movement information. There are only a few studies which provide quantitative data concerning the magnitude of the constancy loss during smooth eye movements, and the results from these experiments are at odds with each other. One of these was a study of the Fikhne illusion (Mack and Herman. 1973). The data from that study indicated that there was only a small loss of position constancy for the background during intervals in which observers pursued a moving stimuius. A version of the nulling technique was used to determine the point of subjective stability for a farge background which entirely filfed the visuat geld. The mean point of subjective stability occurred when the background moved with the target at approximately 199,; of its velocity, which is more appropriately described as an instance of underconstancy than as a complete failure of constancy. The hypothesis tendered to account for this partial constancy loss was that it was the result of an under-registration of smooth eye movement velocity. i.e. the perceptual system has information that the eyes are travelling more slowly than their actual rate of movement. The result is that compensation for image displacements of background objects is only partial since it is fimited by the under-registration of eye movement velocity, This hypothesis gains support from the fact that a moving object appears to move more slowly when tracked than when its image paints over the retina phenomenal slowing seems clear evidence of an under registration of smooth eye movement vetocity information. A similar hypothesis has recently been offered by Yasui and Young (1975). The only other quantitative data concerning the extent of …

Inattentional Blindness Looking Without Seeing

Surprising as it may seem, research shows that we rarely see what we are looking at unless our attention is directed to it. This phenomenon can have serious life-and-death consequences. Although the inextricable link between perceiving and attending was noted long ago by Aristotle, this phenomenon, now called inattentional blindness (IB), only recently has been named and carefully studied. Among the many questions that have been raised about IB are questions about the fate of the clearly visible, yet unseen stimuli, whether any stimuli reliably capture attention, and, if so, what they have in common. Finally, is IB an instance of rapid forgetting, or is it a failure to perceive?

Position constancy during pursuit eye movement: an investigation of the Filehne illusion.

Experiments were performed to investigate the Filehne illusion, the apparent movement of the background during pursuit eye movements. In a dark room subjects tracked a luminous target as it moved at 3°/s or 10.5/s in front of an illuminated background which was either stationary or moved at a fraction of the target speed in the same or opposite direction. Subjects reported whether the background appeared to move and the direction of the movement. Results reveal only a partial loss of position constancy for the background during tracking. The stationary background is perceived to move slightly in the direction opposite to that in which the tracked target is moving. These results seemed best described as an instance of perceptual underconstancy and led to the speculation that the source of the illusion is an underestimation of the rate of pursuit eye movements. An experimental test of this hypothesis which produced supporting evidence is reported.

What we see: Inattention and the capture of attention by meaning

Attention is necessary for the conscious perception of any object. Objects not attended to are not seen. What is it that captures attention when we are engaged in some attention-absorbing task? Earlier research has shown that there are only a very few stimuli which have this power and therefore are reliably detected under these conditions (for example, Mack & Rock, 1998; Moray, 1959). The two most reliable are the observers own name and a happy face icon which seem to capture attention by virtue of their meaning. Three experiments are described which explore whether these stimuli are detected under conditions, heretofore unexamined, which either cause inattentional blindness or are associated with a perceptual failure associated with the limits of attention. The evidence obtained indicates that these stimuli have a unique capacity to capture and extend the limits of attention under conditions in which this has been deemed highly unlikely.

The dissociation of position and extent in Müller-Lyer figures

Three experiments were designed to determine whether Müller-Lyer figures cause a misperception of the positions of their fins and, if they do, whether it is commensurate with the distortion of extent. Observers marked the visible intersection of shaft and fins either with their unseen hands or with their visible hands after the figure had been removed from view. In the former case, no systematic distortions of position were evident. In the latter case, there were small, systematic distortions of position, which were significantly smaller when the observers fixated the target vertex than when they fixated the center of the figure. These differences are discussed in terms of the probable similarities between the control of eye movements and the control of pointing responses. Of particular importance is the finding that even the largest distortions of vertex position were much smaller than the distortions of shaft extent. The results appear to provide evidence of the independence of perceived position from perceived extent in Müller-Lyer figures and to contradict all existing theories of the illusion.

Perceived movement of the afterimage during eye movements

The question of whether an afterimage viewed in a dark field appears to move during eye movement was studied by comparing recordings of eye movements with recordings of reports of perceived movement. The correlation was found to be quite good even under conditions where the eye movements were spontaneous rather than specifically directed. The results were taken to support the hypothesis that the behavior of the retinal image is “interpreted” by taking into account information concerning what the eyes are doing.