Sensory and cognitive components of visual information acquisition.

The authors describe a theory of visual information acquisition and visual memory. The theory has 2 major components. First, the visual system's initial sensory response to a short-duration, low-contrast stimulus is generated by a linear, low-pass temporal filter that operates on the stimulus's temporal waveform. Second, information is acquired from a stimulus through an independent-sampling process whose sampling rate at time t following stimulus onset is jointly proportional to (a) the magnitude by which the sensory response exceeds some threshold and (b) the proportion of still unacquired information. The theory was successfully tested in 5 variants of a digit recall task in which temporal waveform of the stimulus was systematically manipulated. In a final experiment, the theory simultaneously accounted for performance in detection and identification tasks. Implications for visual information processing, low-contrast detection, and binocular combination of information are discussed.

Binocular information acquisition and visual memory.

Mechanisms underlying the binocular combination of visual information were investigated within the context of a visual information acquisition theory proposed by Loftus, Busey, and their colleagues (e.g., as described by T.A. Busey & G. R. Loftus, 1994). A central assumption of the theory is that of a sensory threshold, which engenders an information loss such that information processing subsequent to the threshold is assumed to occur only when the magnitude of a sensory representation triggered by the stimulus exceeds the threshold. The presumed sensory threshold may be situated prior to or subsequent to the point at which the information from the two eyes combines. The location of this threshold was investigated in 3 experiments that provided conclusions about the location of the sensory thresholds and the mechanisms of binocular combination. It is concluded that a linear summation mechanism, an independent sampling information acquisition model, and both pre- and postcombinatorial sources of information loss are required to account for the data.

Localization and identification tasks rely on different temporal frequencies.

The temporal frequencies underlying character localization and identification tasks are measured, as suggested by a model that assumes that the two tasks are processed in different cortical pathways and receive contributions from different populations of visual cortical neurons. Data from two-pulse and temporal contrast sensitivity experiments demonstrate that character localization depends upon much higher temporal frequencies than character identification when both are tested in the periphery. Foveal presentations demonstrate that detection and identification tasks rely on the same temporal frequencies. In a control experiment, the letters were blurred to restrict the range of spatial frequencies. However, these stimuli replicated earlier results and demonstrates that the use of higher temporal frequencies by the localization tasks cannot be attributed to the use of different spatial frequencies for different tasks. In addition, near-foveal presentations of the localization task replicate findings from the far periphery, suggesting that the localization task may be processed differently from the detection task regardless of location on the retina. Finally, the temporal frequency differences persist when a single sine-wave grating is used in localization and identification tasks. The results are consistent with any anatomical model that assumes that the neural substrates underlying localization receive or maintain a higher range of temporal frequencies than areas responsible for identification. The findings demonstrate how the time-course of different stimulus attributes can be quantified, and have implications for theories of information processing in which different stimulus attributes are combined.

Accounts of blending, distinctiveness, and typicality in the false recognition of faces.

The false recognition of distractor faces created from combinations of studied faces has been attributed to the creation of novel traces in memory, although familiarity accounts are also plausible. In 3 experiments, participants studied parent faces and then were tested with a distractor that was created by morphing 2 parents. These produced high false-alarm rates but no effects of a temporal separation manipulation. In a forced-choice version, participants chose the distractor over the parents. R. M. Nosofsky's (1986) Generalized Context Model and variants could account for some but not all aspects of the data. A new model, SimSample, can account for the effects of typicality and distinctiveness, but not for the morph false alarms unless explicit prototypes are included. The conclusions are consistent with an account of memory in which novel traces are created in memory; alternative explanations are also explored.

Accounts of the confidence-accuracy relation in recognition memory.

Confidence and accuracy, while often considered to tap the same memory representation, are often found to be only weakly correlated (e.g., Bothwell, Deffenbacher, & Brigham, 1987; Deffenbacher, 1980). There are at least two possible (nonexclusive) reasons for this weak relation. First, it may be simply due to noise of one sort or another; that is, it may come about because of both within- and between-subjects statistical variations that are partially uncorrelated for confidence measures on the one hand and accuracy measures on the other. Second, confidence and accuracy may be uncorrelated because they are based, at least in part, on different memory representations that are affected in different ways by different independent variables. We propose a general theory that is designed to encompass both of these possibilities and, within the context of this theory, we evaluate effects of four variables--degree of rehearsal, study duration, study luminance, and test luminance--in three face recognition experiments. In conjunction with our theory, the results allow us to begin to identify the circumstances under which confidence and accuracy are based on the same versus different sources of information in memory. The results demonstrate the conditions under which subjects are quite poor at monitoring their memory performance, and are used to extend cue utilization theories to the domain of face recognition.

Temporal inhibition in character identification.

Models of information processing tasks such as character identification often do not consider the nature of the initial sensory representation from which task-relevant information is extracted. An important component of this representation is temporal inhibition, in which the response to a stimulus may inhibit, or in some cases facilitate, processing of subsequent stimuli. Three experiments demonstrate the existence of temporal inhibitory processes in information processing tasks such as character identification and digit recall. An existing information processing model is extended to account for these effects, based in part on models from the detection literature. These experiments also discriminate between candidate neural mechanisms of the temporal inhibition. Implications for the transient deficit theory of dyslexia are discussed.

Providing a sensory basis for models of visual information acquisition.

Our major goal is to account for some simple digit-recall data with a theory that integrates two models from two scientific traditions. The random-sampling model, founded in the memory and attention literature, holds that (1) stimulus features are randomly sampled throughout the course of stimulus presence and (2) proportion correct recall is equal to the ratio of sampled features to total features. The linear-filter model, founded in the vision and sensation literature, holds that the initial stages of the visual system act as a low-pass temporal filter on the input stimulus, resulting in a time-varying sensory response in the nervous system. We report two experiments in which a variable-duration, masked, four-digit string had to be immediately recalled. Experiment 1 was designed principally to replicate past data confirming the basic random-sampling model. Like others, we were able to confirm the model only by endowing it with an additional processing-delay assumption: that feature sampling does not begin until the stimulus has been physically present for some minimal duration. Experiment 2 was an extension of Experiment 1 in which the target stimulus was preceded, 250 msec prior to its onset, by a 50-msec pre-presentation of the same stimulus called a prime. The Experiment 2 results allowed the following conclusions. First, the initial processing delay found in Experiment 1 is immutably tied to stimulus onset; that is, if there are two stimulus onsets, separated even briefly in time, there are two associated processing delays. Second, processing rate is essentially unaffected by the prime's presentation. Third, being presented with a 50-msec prime is equivalent, in terms of memory performance, to increasing unprimed stimulus duration by approximately 30 msec; the prime can thus said to be worth 30 msec of additional exposure duration. This third conclusion seems superficially paradoxical, in the sense that one would expect that having seen a 50-msec prime would be equivalent to increasing exposure duration by at least the same 50 msec. However, both the initial processing delays and the 30-msec prime's worth are natural consequences of our theory that conjoins the random-sampling model with the linear-filter model.

Compensation is unnecessary for the perception of faces in slanted pictures.

In four experiments, we explored the perception of facial distortions seen in pictures viewed from the side or from above or below. In all four, however, we disguised the slant of the picture surface by using a double-projection technique that removed binocular and monocular cues: Faces were digitized, distorted to mimic a particular slant behind the image plane, cropped to a frame, and presented to viewers for their judgments. In the first experiment, we found that simulated rotations around a horizontal axis (pictures seen as if from above or below) created more noticeable distortions in faces than did simulated rotations around a vertical axis (pictures seen as if from the left or right). In the second experiment, pursuing a result from the first but with a between-subjects design, we found that pictured faces with a slant around a vertical axis of 22 degrees were seen as having no more distortion than unslanted faces. In the third experiment, we placed each image within a frame slanted either in the same way as or differently from the picture, and found no effect of frame. In the fourth experiment, we determined that viewers had little ability to match appropriately slanted frames with slanted pictures. Thus, we claim that part of the reason why one can look at moderately slanted pictures without perceptual interference is that the distortions in the image are subthreshold, or perhaps within the bounds of acceptability. These results contrast with the generally accepted theory that viewers mentally compensate for distortions in moderately slanted pictures.