Infants’ perception of curved illusory contour with motion

Recently, Masuda et al. (submitted for publication) showed that adults perceive moving rigid or nonrigid motion from illusory contour with neon color spreading in which the inducer has pendular motion with or without phase difference. In Experiment 1, we used the preferential looking method to investigate whether 3–8-month-old infants can discriminate illusory and non-illusory contour figures, and found that the 7–8-month-old, but not the 3–6-month-old, infants showed significant preference for illusory contour with phase difference. In Experiment 2, we tested the validity of the visual stimuli in the present study, and whether infants could detect illusory contour from the current neon color spreading figures. The results showed that all infants might detect illusory contour figure with neon color spreading figures. The results of Experiments 1 and 2 suggest that 7–8-month-old infants potentially perceive illusory contour from the visual stimulus with phase-different movement of inducers, which elicits the perception of nonrigid dynamic subjective contour in adults.     

Frames of reference for anticipatory action in 4-month-old infants

The spatial representations of 4-month-old infants were examined in two experiments using a modified version of the visual expectation paradigm (VExP). The experiments were designed in order to determine what spatial frames of reference were available to infants for making anticipatory saccades. In Experiment 1, we found that infants most often used a retinocentric frame of reference that did not take into account their current eye position in making an anticipatory saccade. However, Experiment 2 revealed that under certain conditions infants are more likely to make anticipatory saccades consistent with a body- or object-centred frame of reference. The main difference between the two experiments was the degree to which the featural properties of the stimuli varied. The results shed light on the development of spatial representations for action in infancy.     

Developmental changes in visual scanning of face and nonface patterns by infants

The eye movements of infants, aged 4–5, 7–8, and 10–11 weeks, were recorded while they viewed either a representation of a face or a nonface stimulus. Presentation of the visual stimulus was paired with the presentation of an auditory stimulus (either voice or tone) or silence. Attention to the visual stimulus was greater for the older two groups than for the youngest group. The effect of the addition of sound was to increase attention to the visual stimulus. In general, the face was looked at more than the nonface stimulus. The difference in visual attention between the face and the nonface stimulus did not appear to be based solely on the physical characteristics of the stimuli. A sharp increase in the amount of looking at the eyes of the face stimulus at 7–8 weeks of age seemed to be related to a developing appreciation of the meaning of the face as a pattern.     

Effects of multimodal presentation and stimulus familiarity on auditory and visual processing

Two experiments examined the effects of multimodal presentation and stimulus familiarity on auditory and visual processing. In Experiment 1, 10-month-olds were habituated to either an auditory stimulus, a visual stimulus, or an auditory-visual multimodal stimulus. Processing time was assessed during the habituation phase, and discrimination of auditory and visual stimuli was assessed during a subsequent testing phase. In Experiment 2, the familiarity of the auditory or visual stimulus was systematically manipulated by prefamiliarizing infants to either the auditory or visual stimulus prior to the experiment proper. With the exception of the prefamiliarized auditory condition in Experiment 2, infants in the multimodal conditions failed to increase looking when the visual component changed at test. This finding is noteworthy given that infants discriminated the same visual stimuli when presented unimodally, and there was no evidence that multimodal presentation attenuated auditory processing. Possible factors underlying these effects are discussed.     

The development of orientation categories between 2 and 4 months of age

Recent research has indicated that infants are capable of responding to stimuli in a manner indicating that they categorize them. Infant perception of orientation was examined within a framework of categorization. In one experiment, it was shown that 4-month-old infants generalized habituation from one range of oblique grating stimuli to another, consistent with the interpretation that any two oblique stimuli were perceived as more similar than a vertical and an oblique. Four-month-old infants' generalization was not due to a simple inability to discriminate between obliques (Experiment 2) so the results of Experiment 1 reflect in large part true categorization behavior and not categorical perception. Results for 2- and 3-month old infants suggest that "vertical" serves as a reference stimulus in infant orientation perception such that gross distinctions between vertical and nonvertical precede the development of the "oblique" category. The category boundary between oblique and vertical did not successfully predict better between-than within-category discrimination in 4-month-old infants (Experiment 3) under the conditions of these experiments.     

Judgments of synchrony between auditory and moving or still visual stimuli.

The flash-lag effect is a visual illusion wherein intermittently flashed, stationary stimuli seem to trail after a moving visual stimulus despite being flashed synchronously. We tested hypotheses that the flash-lag effect is due to spatial extrapolation, shortened perceptual lags, or accelerated acquisition of moving stimuli, all of which call for an earlier awareness of moving visual stimuli over stationary ones. Participants judged synchrony of a click either to a stationary flash of light or to a series of adjacent flashes that seemingly bounced off or bumped into the edge of the visual display. To be judged synchronous with a stationary flash, audio clicks had to be presented earlier--not later--than clicks that went with events, like a simulated bounce (Experiment 1) or crash (Experiments 2-4), of a moving visual target. Click synchrony to the initial appearance of a moving stimulus was no different than to a flash, but clicks had to be delayed by 30-40 ms to seem synchronous with the final (crash) positions (Experiment 2). The temporal difference was constant over a wide range of motion velocity (Experiment 3). Interrupting the apparent motion by omitting two illumination positions before the last one did not alter subjective synchrony, nor did their occlusion, so the shift in subjective synchrony seems not to be due to brightness contrast (Experiment 4). Click synchrony to the offset of a long duration stationary illumination was also delayed relative to its onset (Experiment 5). Visual stimuli in motion enter awareness no sooner than do stationary flashes, so motion extrapolation, latency difference, and motion acceleration cannot explain the flash-lag effect.     

Discrimination of color and pattern novelty in one-month human infants

Visual discrimination of novel colors and patterns by one-month infants was studied in two experiments where visual reinforcers were presented contingent upon infants' rate of nonnutritive, high-amplitude sucking. Discrimination was measured by recovery of sucking to the presentation of novel visual reinforcing stimuli following decrements in sucking to familiar visual stimuli. In Expt 1, following decrement to familiar stimuli, independent groups received either a change in color, pattern, both color and pattern, or no stimulus change. Reliable recovery was demonstrated for the three stimulus novelty groups relative to the no-change control. Experiment 2, employing achromatic visual reinforcers also showed reliable recovery to pattern change relative to no-change controls. These findings with one-month infants indicate discrimination between familiar and novel visual reinforcers on the basis of color and pattern differences and an increase due to novelty in the reinforcing effectiveness of visual stimuli. Individual subject differences in response decrement magnitude during familiarization were positively correlated with amount of response recovery to novelty.     

Effects of gaze‐aversion on visual‐spatial imagination

Research suggests that averting gaze from an interlocutor can improve both children's and adults' performance in a range of cognitive tasks. With the present experiments, we investigated the effect of gaze aversion on adults' visual‐spatial imagination, using a methodology adapted from Kerr (1987). Participants mentally kept track of a pathway through an imaginary matrix, while either maintaining eye‐contact with the experimenter, closing their eyes, gazing at a static or a dynamic visual stimulus (in Experiment 1), or fixating an upright or inverted image of the experimenter's face (in Experiment 2). The results show that whereas maintaining eye‐contact with another person disrupts accurate imagination of this pathway, averting gaze or looking at other visual stimuli does not. We conclude that gaze aversion benefits cognitive performance, not just by disengaging visual attention from irrelevant visual information, but also by interrupting social interaction processes involved in face‐to‐face communication.     

Pre-verbal infants perceive emotional facial expressions categorically

Adults perceive emotional expressions categorically, with discrimination being faster and more accurate between expressions from different emotion categories (i.e. blends with two different predominant emotions) than between two stimuli from the same category (i.e. blends with the same predominant emotion). The current study sought to test whether facial expressions of happiness and fear are perceived categorically by pre-verbal infants, using a new stimulus set that was shown to yield categorical perception in adult observers (Experiments 1 and 2). These stimuli were then used with 7-month-old infants (N = 34) using a habituation and visual preference paradigm (Experiment 3). Infants were first habituated to an expression of one emotion, then presented with the same expression paired with a novel expression either from the same emotion category or from a different emotion category. After habituation to fear, infants displayed a novelty preference for pairs of between-category expressions, but not within-category ones, showing categorical perception. However, infants showed no novelty preference when they were habituated to happiness. Our findings provide evidence for categorical perception of emotional expressions in pre-verbal infants, while the asymmetrical effect challenges the notion of a bias towards negative information in this age group.     

S-R compatibility effects due to context-dependent spatial stimulus coding

Responses are faster with spatial S-R correspondence than with noncorrespondence (spatial compatibility effect), even if stimulus location is irrelevant (Simon effect). In two experiments, we sought to determine whether stimuli located above and below a fixation point are coded as left and right (and thus affect the selection of left and right responses) if the visual context suggests such a coding. So, stimuli appeared on the left or right eye of a face’s image that was tilted by 90° to one side or the other (Experiment 1) or varied between upright and 45° or 90° tilting (Experiment 2). Whether stimulus location was relevant (Experiment 1) or not (Experiment 2), responses were faster with correspondence of (face-based) stimulus location and (egocentrically defined) response location, even if stimulus and response locations varied on physically orthogonal dimensions. This suggests that object-based spatial stimulus codes are formed automatically and thus influence the speed of response selection.     

Multimodal events and moving locations: eye movements of adults and 6-month-olds reveal dynamic spatial indexing

The ability to keep track of locations in a dynamic, multimodal environment is crucial for successful interactions with other people and objects. The authors investigated the existence and flexibility of spatial indexing in adults and 6-month-old infants by adapting an eye-tracking paradigm from D. C. Richardson and M. J. Spivey (2000). Multimodal events were presented in specific locations, and eye movements were measured when the auditory portion of the stimulus was presented without its visual counterpart. Experiment 1 showed that adults spatially index auditory information even when the original associated locations move. Experiments 2 and 3 showed that infants are capable of both binding multimodal events to locations and tracking those locations when they move.     

Stimulus control and the growth of the infant’s effective visual field*

The size of the infant’s effective visual field was studied weekly in infants starting at 2 weeks of age until they were 10 weeks old, The field was initially quite small, 15 deg to either side of their line of regard. Over the 2-month period of the study, it more than doubled for stimulus conditions in which the peripheral event was in motion and the fixation object static, and it remained approximately the same size when motion was present in the fixation event and the peripheral object was static. As with adults, the infant’s effective visual field is directly related to the stimuli available.     

Infants’ representations of same and different in match- and non-match-to-sample

Three experiments investigated the representations that underlie 14-month-old infants’ and adults’ success at match-to-sample (MTS) and non-match-to-sample (NMTS) tasks. In Experiment 1, 14-month-old infants were able to learn rules based on abstract representations of sameness and/or difference. When presented with one of eighteen sample stimuli (A) and a choice between a stimulus that was the same as the sample (A) and a different stimulus (B), infants learned to choose A in MTS and B in NMTS. In Experiments 2 and 3, we began to explore the nature of the representations at play in these paradigms. Experiment 2 confirmed that abstract representations were at play, as infants generalized the MTS and NMTS rules to stimuli unseen during familiarization. Experiment 2 also showed that infants tested in MTS learned to seek the stimulus that was the same as the sample, whereas infants tested in NMTS did not learn to seek the different stimulus, but instead learned to avoid the stimulus that was the same as the sample. Infants appeared to only use an abstract representation of the relation same in these experiments. Experiment 3 showed that adult participants, despite knowing the words “same” and “different”, also relied on representations of sameness in both MTS and NMTS in a paradigm modeled on that of Experiment 2. We conclude with a discussion of how young infants may possibly represent the abstract relation same.     

The perception of identity by 6 1/2-month-old infants.

In Study 1, sixteen 6 1/2-month-olds were habituated to a Reversible stimulus (an upright face that could be perceived as an entirely different upright face when it was rotated 180 degrees) and to a Nonreversible stimulus (a face that could be perceived as upright in only one orientation). Following habituation for each type of stimulus, test trials paired the habituated face with a novel stimulus (an inversion of the same face). For both Reversible and Nonreversible stimuli, the physical difference between the old and new test stimuli was the same (a 180 degrees rotation); however, infants devoted more visual attention to the 180 degrees rotation only when it was a Reversible face, suggesting that the identity change was detected. Experiment 2 ruled out the explanation that infants might have failed to dishabituate to the inversion of the Nonreversible stimulus because they could not remember it. Results are interpreted as evidence that 6 1/2-month-old infants are not limited to face recognition based on similarity in pattern arrangement alone, but are capable of processing faces at a representational level.     

Relative mislocalization of briefly presented stimuli in the retinal periphery

We studied the ability to localize flashed stimuli, using a relative judgment task. When observers are asked to localize the peripheral position of a probe with respect to the midposition of a spatially extended comparison stimulus, they tend to judge the probe as being more toward the periphery than is the midposition of the comparison stimulus. We report seven experiments in which this novel phenomenon was explored. They reveal that the mislocalization occurs only when the probe and the comparison stimulus are presented in succession, independent of whether the probe or the comparison stimulus comes first (Experiment 1). The size of the mislocalization is dependent on the stimulus onset asynchrony (Experiment 2) and on the eccentricity of presentation (Experiment 3). In addition, the illusion also occurs in an absolute judgment task, which links mislocalization with the general tendency to judge peripherally presented stimuli as being more foveal than they actually are (Experiment 4). The last three experiments reveal that relative mislocalization is affected by the amount of spatial extension of the comparison stimulus (Experiment 5) and by its structure (Experiments 6 and 7). This pattern of results allows us to evaluate possible explanations of the illusion and to relate it to comparable tendencies observed in eye movement behavior. It is concluded that the system in charge of the guidance of saccadic eye movements is also the system that provides the metric in perceived visual space.     

Infant sensitivity to figural coherence in biomechanical motions

Two experiments assessed infant sensitivity to figural coherence in point-light displays moving as if attached to the major joints of a walking person. Experiment 1 tested whether 3- and 5-month-old infants could discriminate between upright and inverted versions of the walker in both moving and static displays. Using an infant-control habituation paradigm, it was found that both ages discriminated the moving but not the static displays. Experiment 2 was designed to clarify whether or not structural invariants were extracted from these displays. The results revealed that (1) moving point-light displays with equivalent motions but different topographic relations were discriminated while (2) static versions were not, and (3) arrays that varied in the amount of motion present in different portions of the display were also not discriminated. These results are interpreted as indicating that young infants are sensitive to figural coherence in displays of biomechanical motion.     

Where does attention go when you blink?

Many studies have shown that covert visual attention precedes saccadic eye movements to locations in space. The present research investigated whether the allocation of attention is similarly affected by eye blinks. Subjects completed a partial-report task under blink and no-blink conditions. Experiment 1 showed that blinking facilitated report of the bottom row of the stimulus array: Accuracy for the bottom row increased and mislocation errors decreased under blink, as compared with no-blink, conditions, indicating that blinking influenced the allocation of visual attention. Experiment 2 showed that this was true even when subjects were biased to attend elsewhere. These results indicate that attention moves downward before a blink in an involuntary fashion. The eyes also move downward during blinks, so attention may precede blink-induced eye movements just as it precedes saccades and other types of eye movements.     

Fixation disengagement and eye-movement latency

We examined eye-movement latencies to a target that appeared during visual fixation of a stationary stimulus, a moving stimulus, or an extrafoveal stimulus. The stimulus at fixation was turned off either before target onset (gap condition) or after target onset (overlap condition). Consistent with previous research, saccadic latencies were shorter in gap conditions than they were in overlap conditions (the gap effect). In Experiment 1, a gap effect was observed for vergence eye movements. In Experiment 2, a gap effect was observed for saccades directed at a target that appeared during visual pursuit of a moving stimulus. In Experiment 3, a gap effect was observed for saccades directed at a target that appeared during extrafoveal fixation. The present results extend reports of the gap effect for saccadic shifts during visual fixation to (a) vergence shifts during visual fixation, (b) saccadic shifts during smooth visual pursuit, and (c) saccadic shifts during extrafoveal fixation. The present findings are discussed with respect to the incompatible goals of fixation-locking and fixation-shifting oculomotor responses.     

Perception of internal elements of compound figures by one-month-old infants

Previous research has shown that infants younger than 2 months frequently concentrate their attention on peripheral or external features of visual stimuli and that they do not appear to process the internal elements of a compound visual stimulus composed of a simple geometric figure enclosed in a larger figure. A visual habituation-dishabituation paradigm was used to determine whether 1-month-old infants would process internal information if the internal elements of the stimulus were patterns often found to be preferred by young infants. Four groups of eight infants each were habituated to a compound stimulus consisting of a square or triangle surrounding a checkerboard or bull's-eye. Following habituation each group was presented with one of four types of stimulus: the identical stimulus (control group), a stimulus differing only in the internal component, a stimulus differing only in the external component, or a stimulus differing in both components. The results of the present study suggest that when the internal element of a compound stimulus is a highly preferred or salient stimulus, the young infant will process information about its characteristics.     

Different effects of eyelid blinks and target blanking on saccadic suppression of displacement

Displacements of visual stimuli during saccadic eye movements are often not noticed. We have demonstrated that saccadic suppression of image displacement can be eliminated by blanking the stimulus for a short period during and after the saccade (Deubel, Schneider, & Bridgeman, 1996). Here we report an experiment in which target visibility was interrupted after the saccade, either by distal target blanking or by voluntary eyeblink. The data show that the effect of blinking is different from blanking; interruption of vision due to a blink did not enable subjects to detect target displacements any better than they had done in the no-blank condition. The results provide evidence for an extraretinal signal that distinguishes between endogenous and exogenous sources of temporary object disappearance after the saccade.