Jay A. Edelman

Information Processing during Face Recognition: The Effects of Familiarity, Inversion, and Morphing on Scanning Fixations:

Where we make ocular fixations when viewing an object likely reflects interactions between ‘external’ object properties and internal ‘top - down’ factors, as our perceptual system tests hypotheses and attempts to make decisions about our environment. These scanning fixation patterns can tell us how and where the visual system gathers information critical to specific tasks. We determined the effects of the internal factors of expertise, experience, and ambiguity on scanning during a face-recognition task, in eight subjects. To assess the effects of expertise, we compared upright with inverted faces, since it is hypothesized that inverted faces do not access an orientation-dependent face-expert processor. To assess the effects of experience, we compared famous with novel faces, as famous faces would have stronger internal representations than anonymous ones. Ambiguity in matching seen and remembered faces was manipulated with morphed faces. We measured three classes of variables: (i) total scanning time and fixations; (ii) the spatial distribution of scanning; and (iii) the sequence of scanning, using first-order Markov matrices for local scan structure and string editing for global scan structure. We found that, with inverted faces, subjects redistributed fixations to the mouth and lower face, and their local and global scan structure became more random. With novel or morphed faces, they scanned the eyes and upper face more. Local scan structure was not affected by familiarity, but global scan structure was least random (most stereotyped) for novel upright faces. We conclude that expertise (upright faces) leads to less lower-face scanning and more predictable global patterns of information gathering. Experience (famous faces) leads to less upper-face scanning and more idiosyncratic global scan structures, suggesting a superseding influence of facial memories. With morphed faces, subjects return to the upper face to resolve ambiguity, implying a greater importance of this region in face recognition.

Inhibition of voluntary saccadic eye movement commands by abrupt visual onsets.

Saccadic eye movements are made both to explore the visual world and to react to sudden sensory events. We studied the ability for humans to execute a voluntary (i.e., nonstimulus-driven) saccade command in the face of a suddenly appearing visual stimulus. Subjects were required to make a saccade to a memorized location when a central fixation point disappeared. At varying times relative to fixation point disappearance a visual distractor appeared at a random location. When the distractor appeared at locations distant from the target virtually no saccades were initiated in a 30- to 40-ms interval beginning 70-80 ms after appearance of the distractor. If the distractor was presented slightly earlier relative to saccade initiation then saccades tended to have smaller amplitudes, with velocity profiles suggesting that the distractor terminated them prematurely. In contrast, distractors appearing close to the saccade target elicited express saccade-like movements 70-100 ms after their appearance, although the saccade endpoint was generally scarcely affected by the distractor. An additional experiment showed that these effects were weaker when the saccade was made to a visible target in a delayed task and still weaker when the saccade itself was made in response to the abrupt appearance of a visual stimulus. A final experiment revealed that the effect is smaller, but quite evident, for very small stimuli. These results suggest that the transient component of a visual response can briefly but almost completely suppress a voluntary saccade command, but only when the stimulus evoking that response is distant from the saccade goal.

Antisaccade velocity, but not latency, results from a lack of saccade visual guidance

Antisaccades are slower in peak velocity, more dysmetric, and longer in latency than prosaccades. This study used a novel visually guided antisaccade task to determine how visual target presence affects antisaccade metrics. The results showed that peak velocity and endpoint error of visually guided antisaccades were more similar to prosaccades than to traditional antisaccades, whereas their latencies were similar to those of traditional antisaccades. The velocity of prosaccades, and to a lesser extent that of antisaccades, were boosted by the sudden appearance of a target. These results suggest that the lower velocity and increased dysmetria of traditional antisaccades result from the absence of a visual target, but their longer latency is more likely a result of suppressing a prosaccadic reflex.

The influence of object-relative visuomotor set on express saccades

Express saccades are considered to have the shortest latency (70-110 ms) of all saccadic eye movements. The influence of visuomotor set, preparatory processes that spatially affect a sensorimotor response, on express saccades was examined by instructing human subjects to make a saccade to one of two simultaneously appearing spots defined by its position relative to the other. A temporal gap between fixation point disappearance and target appearance was used to facilitate the production of express saccades. For all subjects, the instruction influenced the vector of express saccades without increasing saccade latency. The effect on express saccades was only slightly weaker than that for longer latency saccades. Saccade curvature was minimal and did not depend strongly on task. Further experiments demonstrated that the effect of instruction on express saccade vector was much weaker when saccades were instructed to be made to one side of a single small spot, that the effect of instruction was equally strong when directing saccades to the less salient of two stimuli, and that an instruction could not only determine the direction of the effect but also modulate the effects magnitude. The effect of instruction on saccade vector was no higher when blocked than when varied across trials. These results suggest that express saccades are influenced by object-relative spatial preparatory processes without increasing their reaction time and, thus, that high-level cognitive processes can influence the most reflexive of saccadic eye movements.

Scan patterns during the processing of facial identity in prosopagnosia

The scan patterns of ocular fixations made by prosopagnosic patients while they attempt to identify faces may provide insights into how they process the information in faces. Contrasts between their scanning of upright versus inverted faces may index the presence of a hypothesized orientation-dependent expert mechanism for processing faces, while contrasts between their scanning of familiar versus novel faces may index the influence of residual facial memories on their search for meaningful facial information. We recorded the eye movements of two prosopagnosics while they viewed faces. One patient, with acquired prosopagnosia from a right occipitotemporal lesion, showed degraded orientation effects but still with a normal distribution of fixations to more salient facial features. However, the dynamics of his global scan patterns were more chaotic for novel faces, suggesting degradation of an internal facial schema, and consistent with other evidence of impaired face configuration perception in this patient. His global scan patterns for famous faces differed from novel faces, suggesting the influence of residual facial memories, as indexed previously by his relatively good imagery for famous faces. The other patient, with a developmental prosopagnosia, showed anomalous orientation effects, abnormal distribution of fixations to less salient regions, and chaotic global scan patterns, in keeping with a more severe loss of face-expert mechanisms. The effects of fame on her scanning were weaker than those in the first subject and non-existent in her global scan patterns. We conclude that scan patterns in prosopagnosia can both reflect the loss of orientation-dependent expert mechanisms and index the covert influence of residual facial memories. In these two subjects the scanning data were consistent with other results from tests of configuration perception, imagery, and covert recognition.

The dependence of visual scanning performance on search direction and difficulty.

Phillips and Edelman [Phillips, M. H., & Edelman, J. A. (2008). The dependence of visual scanning performance on saccade, fixation, and perceptual metrics. Vision Research, 48(7), 926-936] presented evidence that performance variability in a visual scanning task depends on oculomotor variables related to saccade amplitude rather than fixation duration, and that saccade-related metrics reflects perceptual span. Here, we extend these results by showing that even for extremely difficult searches trial-to-trial performance variability still depends on saccade-related metrics and not fixation duration. We also show that scanning speed is faster for horizontal than for vertical searches, and that these differences derive again from differences in saccade-based metrics and not from differences in fixation duration. We find perceptual span to be larger for horizontal than vertical searches, and approximately symmetric about the line of gaze.

Prepare for conflict: EEG correlates of the anticipation of target competition during overt and covert shifts of visual attention.

When preparing to make a saccadic eye movement in a cued direction, perception of stimuli at the target location is enhanced, just as it is when attention is covertly deployed there. Accordingly, the timing and anatomical sources of preparatory brain activity accompanying shifts of covert attention and saccade preparation tend to exhibit a large degree of overlap. However, there is evidence that preparatory processes are modulated by the foreknowledge of visual distractor competition during covert attention, and it is unknown whether eye movement preparation undergoes equivalent modulation. Here we examine preparatory processes in the electroencephalogram of human participants during four blocked versions of a spatial cueing task, requiring either covert detection or saccade execution, and either containing a distractor or not. As in previous work, a typical pattern of spatially selective occipital, parietal and frontal activity was seen in all task versions. However, whereas distractor presence called on an enhancement of spatially selective visual cortical modulation during covert attention, it instead called on increased activity over frontomedial oculomotor areas in the case of overt saccade preparation. We conclude that, although advance orienting signals may be similar in character during overt and covert conditions, the pattern by which these signals are modulated to ameliorate the behavioral costs of distractor competition is highly distinct, pointing to a degree of separability between the overt and covert systems.

The Influence of Motor Training on Human Express Saccade Production

Express saccadic eye movements are saccades of extremely short latency. In monkey, express saccades have been shown to occur much more frequently when the monkey has been trained to make saccades in a particular direction to targets that appear in predictable locations. Such results suggest that express saccades occur in large number only under highly specific conditions, leading to the view that vector-specific training and motor preparatory processes are required to make an express saccade of a particular magnitude and direction. To evaluate this hypothesis in humans, we trained subjects to make saccades quickly to particular locations and then examined whether the frequency of express saccades depended on training and the number of possible target locations. Training significantly decreased saccade latency and increased express saccade production to both trained and untrained locations. Increasing the number of possible target locations (two vs. eight possible targets) led to only a modest increase of saccade latency. For most subjects, the probability of express saccade occurrence was much higher than that expected if vector-specific movement preparation were necessary for their production. These results suggest that vector-specific motor preparation and vector-specific saccade training are not necessary for express saccade production in humans and that increases in express saccade production are due in part to a facilitation in fixation disengagement or else a general enhancement in the ability of the saccadic system to respond to suddenly appearing visual stimuli.

The Relationship between Biology Classes and Biological Reasoning and Common Heath Misconceptions

Abstract This study investigates the relationship among (1) college major, (2) knowledge used in reasoning about common health beliefs, and (3) judgment about the accuracy of those beliefs. Seventy-four college students, advanced biology and non—science majors, indicated their agreement or disagreement with commonly believed, but often inaccurate, statements about health and explained their reasoning. The results indicated that while the direct impact of college-level biology coursework on judgment accuracy was minimal, biology major was associated with increased reliance on advanced biological reasoning, which mediated judgment accuracy. However, the overall association of advanced biological reasoning with judgment accuracy was small. The discussion calls for strengthening the science—daily life connection in biology education for majors and nonmajors.

The effect of object-centered instructions in Cartesian and polar coordinates on saccade vector

Express saccades (ES) are the most reflexive saccadic eye movements, with very short reaction times of 70–110 ms. It is likely that ES have the shortest saccade reaction times (SRTs) possible given the known physiological and anatomical delays present in sensory and motor systems. Nevertheless, it has been demonstrated that a vector displacement of ES to spatially extended stimuli can be influenced by spatial cognition. Edelman, Kristjansson, and Nakayama (2007) found that when two horizontally separated visual stimuli appear at a random location, the spatial vector, but not the reaction time, of human ES is strongly influenced by an instruction to make a saccade to one side (either left or right) of a visual stimulus array. Presently, we attempt to extend these findings of cognitive effects on saccades in three ways: (a) determining whether ES could be affected by other types of spatial instructions: vertical, polar amplitude, and polar direction; (b) determining whether these spatial effects increased with practice; and (c) determining how these effects depended on SRTs. The results demonstrate that both types of Cartesian as well as polar amplitude instructions strongly affect ES vector, but only modestly affect SRTs. Polar direction instructions had sizable effects only on nonreflexive saccades where the visual stimuli could be viewed for several hundred milliseconds prior to saccade execution. Short- (trial order within a block) and long-term (experience across several sessions) practice had little effect, though the effect of instruction increased with SRT. Such findings suggest a generalized, innate ability of cognition to affect the most reflexive saccadic eye movements.