Relative judgment seems to be the key: revisiting the Beck effect.

In multiple-stimulus presentation, orientation disparity has been known to be more discriminable than disparity in line arrangement (e.g., J. Beck, 1972). The source of the effect and its locus were studied in 7 experiments. In different experiments a discrimination between an upright T and either a tilted T or an L, or a discrimination between a tilted T and an L, was required, either in a single stimulus presentation or in the context of upright Ts. Number of stimuli, location uncertainty, and adjacency between stimuli were manipulated. The results indicated that the effect is insensitive to these factors, which is incommensurate with predictions from several accounts of the effect. All the effect requires is that disparate stimuli are simultaneously presented, suggesting that relative judgment is a necessary condition for its manifestation. The effect surfaces when the task calls for procedures based on perception of homogeneity or salience.

A case of a dual frame of reference.

It is demonstrated that observers may relate to two parts of the same object by using two different frames of reference. Subjects were asked to indicate directions within a model of a hallway in which signs were posted on a single prism. The majority of subjects interpreted a sign frontally facing them as indicating the direction which is ahead of them, yet they interpreted an adjacent sign that was slanted with respect to the frontal plane as indicating a direction which is at the same side of the line of sight as the sign is. This manifests a mixture of an egocentric and an object-centred frame of reference, that is reminiscent of the mixture of local spatial interpretations in impossible pictures. It is suggested that frames of reference are not necessarily unique in a given percept, and that they are not derived from a global computation.

Testing a queue hypothesis for the processing of global and local information.

To test whether the advantage for global features in visual perception is stationary throughout the course of processing or is superseded by a local advantage, 6 experiments were conducted in which subjects responded to auditorially presented letter names, while viewing compound visual stimuli. The consistencies of the 2 levels of the compound letters with the auditory stimuli were varied. The requirement with respect to the visual stimulus was manipulated between experiments. The onset asynchrony (SOA) between the visual stimulus and the auditory one was randomized within blocks. Interaction of SOA with consistency of either of the globality levels with the auditory stimulus would indicate lack of stationarity. No such indication was found. Several findings suggest global advantage. The results hold across 3 exposure durations. Findings support the hypothesis of global precedence as well as the claim that it is stationary.

Role of outcome conflict in dual-task interference.

The traditional explanation for dual-task interference is that tasks compete for scarce processing resources. Another possible explanation is that the outcome of the processing required for one task conflicts with the processing required for the other task (e.g., cross talk). To explore the contribution of outcome conflict to task interference, we manipulated the relatedness of the tasks. In Experiment 1, subjects searched concurrently for names of boys in one channel and names of cities in another channel. Responses were significantly delayed when a nontarget on one channel belonged to, or was even just related to, the category designated as the target for the other channel. No comparable effects were found when the tasks were performed in isolation. Thus, the difficulty of the individual tasks is not the only determinant of how much they will interfere when combined, and there must be substantial interactions between processes carrying out the two tasks. In Experiment 2 subjects searched one channel for specific target letters and another channel for specific target digits. The nontargets in a channel were either from the same alphanumeric category as the targets for that channel or from the opposite category (i.e., the category of the targets for the other channel). It was found that although between-category search was more efficient than within-category search in single tasks, it was less efficient in dual tasks. Thus, there appear to be significant task interactions due to the confusability emerging when the nontargets of one task belong to the same category as the targets of the concurrent task. In addition, the congruence of target presence or absence on the two channels was found to have a sizeable effect. We suggest four potential sources of outcome conflict that may contribute to dual-task interference, and we conjecture that a great deal of the residual interference might result from other sorts of outcome conflict.

The role of carcinoembryonic antigen in surveillance of patients with choroidal malignant melanoma: a prospective study.

Serum carcinoembryonic antigen levels were measured in nine patients with choroidal malignant melanoma prior to enucleation and at three-month intervals thereafter for three years. Raised levels were found preoperatively in four of the nine patients. One of these patients had persistent and progressive elevation of serum carcinoembryonic antigen levels postoperatively, and clinical evidence of metastases subsequently became apparent. In the remaining eight patients, carcinoembryonic antigen levels remained at or returned to normal values and no clinical evidence of progression of the disease was detected. These results suggest that although serum carcinoembryonic antigen estimation is not a reliable diagnostic screening test for choroidal malignant melanoma, it may be useful for follow-up and monitoring of recurrences of the disease.

On separability of and interference between tracking dimensions in dual-axis tracking.

Time-shared tasks may conceivably be separable or integral. A case in which the question of separability seems quite relevant is dual-axis tracking. To test the interaction between tracking dimensions, we first studied whether they interfere with each other. Practiced subjects performed tracking on one or two axes, with or without feedback indicators and with or without a requirement to allocate resources unevenly between axes. They also performed with or without a concurrent binary classification of visually presented digits which were presented within a moving square that served as the target for tracking. Small deficits were found in the performance of both tracking and digit classification when performed together. However, the conditions of tracking did not have a discernible effect on either tracking or digit classification. Hence, the introduction of a second tracking axis probably does not have harmful consequences either on tracking itself or on any other task time-shared with tracking. Further studies were conducted to examine whether the absence of an effect of number of tracking axes is dues to their integrality. Ordinary position tracking was paired either with another similar task on the other axis or with a novel sort of tracking in which subjects had to continually match sizes of moving rectangles. Tasks were paired under both divided-attention and focused-attention instructions. No interference on position tracking was observed even when the types of task on the two axes differed, and no other evidence for integrality of the homogeneous task pairs was found.

Does global precedence really depend on visual angle?

Global advantage has been found in some studies to hold only in stimuli subtending no more than 7 degrees - 10 degrees of visual angle. We argue that those studies confounded globality and eccentricity. To avoid this confound we used stimuli with all their elements located along their perimeter (e.g., Cs and circles). These were presented in two visual angle conditions, small (2 degrees) and large (17.25 degrees). In Experiment 1 subjects had to indicate either the direction of an opening of a C made up of circles or of Cs that were the elements of a circle. Contrary to previous findings, global advantage was found for both large and small visual angle conditions. Results from a control condition seem to indicate that the major determinant of that global advantage was relative size. In Experiment 2 subjects responded to the global or local levels of right- or left-facing Cs made up of right- or left-facing Cs. For the small visual angle condition, the global level interfered with processing of the local level, but not vice versa. For the large visual angle, however, interference effects were smaller and symmetrical, even though a sizeable difference in mean reaction time was observed between the responses to the local and global levels. It is suggested that the time it takes to respond to a level when relevant and the level's effectiveness as a distractor when irrelevant are determined at two different stages of processing.

Bilateral optic atrophy associated with abnormality of chromosome No. 2.

A one year old female infant with mental and motor retardation and bilateral optic atrophy in association with pericentric inversion of chromosome No. 2 is described.

How many trees does it take to make a forest?

In order to study the relative perceptual availability of global and local features in very sparse patterns, subjects were asked to make 'same'/'different' judgments on pairs of geometrical figures and the times needed to detect global and local differences were compared. With triangular patterns a global precedence was found which could be attributed to size differences. With rectangular patterns global precedence was larger, not accounted for by size differences, and indifferent both to the number of elements and to their spacing. Thus it was demonstrated that global precedence may hold for patterns with as few as four elements. Patterns with smooth edges could be compared much more quickly than patterns with serrated eges. It is proposed that configurational properties of some of the patterns interfered with the encoding of their global structures or with comparing them. It is argued that the results support a principle of global addressability which postulates that visual schemata are mainly addressed through their global constituents.

Different difficulty manipulations interact differently with task emphasis: evidence for multiple resources.

To test the notion of multiple resources, a two-dimensional pursuit tracking task was paired with a letter-typing task, the difficulty of which was manipulated by varying cognitive (size of stimulus set) and motor (repetitiveness of finger chords) factors. In addition, task priority was manipulated. The latter factor had a large effect on the performance of the two tasks, which indicates that they compete for resources. Both types of typing difficulty manipulations affected typing performance, but only motor difficulty interacted with priorities. Since difficulty manipulations that tap resources common to both tasks are predicted to interact with priorities, the results are interpreted to indicate that in joint performance, typing and tracking compete mainly for motor-related concept, the letter-typing task is argued to require at least two kinds of resources.

Do attention and decision follow perception Comment on Miller.

In response to Miller's discussion of global precedence, I argue that (a)although perceptual precedence is not the only explanation for asymmetric interference, in some cases it is the most reasonable one; (b) since global precedence does not entail that local and global information cannot interact in their effects on responses, the finding that they do is not incompatible with global precedence; (c) it is dubious that attention or decision are applied just to the resultant of perception rather than determining it or constituting part of it. However, I share some of Miller's doubts about the unique contribution of asymmetric interference data in deciding the issue of global precedence.

Does integration produce masking or protect from it?

To examine the role of integration in pattern masking, possible disruptive effects of integration were minimized by using a mask that overlaid completely all targets. Exposure durations were 10 ms, so under energy summation the target area was much darker than the rest. In another condition the mask was red and targets were blue, so under energy summation the target area could also be distinguished by hue. Masking magnitude increased with delay of mask onset, and it was established by four independent criteria that integration was negligible in the condition which produced most masking. It is deduced that integration is not necessary for masking; furthermore it is suggested that integration never produces masking, but rather may or may not protect from a disruptive effect of interruption. The argument is that were the visual system to have better visual resolution, it would suffer more given the same masking parameters. It is argued that type B masking functions arise from a combination of the facilitatory effect of integration and the detrimental effect of interruption.

Myotonic dystrophy: pathological study of the eyes.

A 56-year-old patient with histopathologically established myotonic dystrophy is described. Gross pathological examination of the eyes revealed cataracts and peripheral retinal dystrophy as described previously. Lacy vacuolization of the pigment epithelium of the iris and vacuolization of the nonpigmentary ciliary epithelium were also found. These latter findings have, to our knowledge, not been hereto described in the literature.

Carcinoembryonic antigen in aqueous humor of patients with primary malignant choroidal melanoma.

Carcinoembryonic antigen levels were simultaneously determined in the aqueous humor and in the plasma of the 3 patients with primary choroidal malignant melanoma undergoing enucleation. An elevated carcinoembryonic antigen level was detected in the aqueous humor of 1 patient with no increase in plasma CEA level. In the other 2 patients no such elevation was found. A local increase of CEA levels produced by the tumor is likely to occur. Further studies are required of CEA levels of patients with primary malignant choroidal melanoma as an aid in diagnosis and treatment of this condition.