Infants’ ability to respond to depth from the retinal size of human faces: Comparing monocular and binocular preferential-looking

To examine sensitivity to pictorial depth cues in young infants (4 and 5 months-of-age), we compared monocular and binocular preferential looking to a display on which two faces were equidistantly presented and one was larger than the other, depicting depth from the size of human faces. Because human faces vary little in size, the correlation between retinal size and distance can provide depth information. As a result, adults perceive a larger face as closer than a smaller one. Although binocular information for depth provided information that the faces in our display were equidistant, under monocular viewing, no such information was provided. Rather, the size of the faces indicated that one was closer than the other. Infants are known to look longer at apparently closer objects. Therefore, we hypothesized that infants would look longer at a larger face in the monocular than in the binocular condition if they perceived depth from the size of human faces. Because the displays were identical in the two conditions, any difference in looking-behavior between monocular and binocular viewing indicated sensitivity to depth information. Results showed that 5-month-old infants preferred the larger, apparently closer, face in the monocular condition compared to the binocular condition when static displays were presented. In addition, when presented with a dynamic display, 4-month-old infants showed a stronger ‘closer’ preference in the monocular condition compared to the binocular condition. This was not the case when the faces were inverted. These results suggest that even 4-month-old infants respond to depth information from a depth cue that may require learning, the size of faces.     

Infants’ sensitivity to the depth cue of shading

Five- and 7-month-old infants were tested for sensitivity to the depth cue of shading. Infants were presented with two displays: a surface in which a convexity and a concavity were molded and a photograph in which shading specified a convexity and a concavity. Each display was presented under both monocular and binocular viewing conditions. Reaching was observed as the dependent measure. Infants in both age groups reached preferentially for the actual convexity in both the monocular and binocular viewing conditions. In the monocular photograph condition, the 7-month-olds reached preferentially for the apparent convexity specified by shading, indicating that they perceived it to be an actual convexity. These infants showed no significant reaching preference in the binocular photograph condition. This finding rules out interpretations of the infants’ reaching not based on perceived depth. The results therefore suggest that the 7-month-olds perceived depth from shading. The 5-month-olds showed no significant reaching preferences when viewing the photograph; thus, they showed no evidence of depth perception from shading. These findings are consistent with the results of a number of studies that have investigated infants’ sensitivity to pictorial depth cues. Together, these studies suggest that the ability to perceive depth from pictorial cues may first develop between 5 and 7 months of age.     

A comparison of monocular and binocular depth perception in 5- and 7-month-old infants

Monocular depth perception was compared with binocular depth perception in 5- and 7-month-old infants. Reaching was used as the dependent measure. Two objects, identical except in size, were presented simultaneously to each infant. The smaller object was within reach for the infants while the larger object was just beyond reach. The two objects subtended equal visual angles from the infants' observation point. With binocular presentation, 96% of the 7-month-olds' reaches and 89% of the 5-month-olds' reaches were for the nearer object. With monocular presentation, 58% of the 7-month-olds' reaches and 65% of the 5-month-olds' reaches were for the nearer object. The reaching preferences observed in the monocular condition indicated sensitivity to monocular depth information (motion parallax, accommodation, and relative size information were available). Binocular viewing, however, resulted in a far more consistent tendency to reach for the nearer object. This result suggests that the infants' perception of the objects' distances was more veridical in the binocular condition than in the monocular condition.     

Binocular vision and spatial perception in 4- and 5-month-old infants

Four experiments investigated the relation between the development of binocular vision and infant spatial perception. Experiments 1 and 2 compared monocular and binocular depth perception in 4- and 5-month-old infants. Infants in both age groups reached more consistently for the nearer of two objects under binocular viewing conditions than under monocular viewing conditions. Experiments 3 and 4 investigated whether the superiority of binocular depth perception in 4-month-olds is related to the development of sensitivity to binocular disparity. Under binocular viewing conditions in Experiment 3, infants identified as disparity-sensitive reached more consistently for the nearer object than did infants identified as disparity-insensitive. The two groups' performances did not differ under monocular viewing conditions. These results suggest that, binocularly, the disparity-sensitive infants perceived the objects' distances more accurately than did the disparity-insensitive infants. In Experiment 4, infants were habituated to an object, then presented with the same object and a novel object that differed only in size. Disparity-sensitive infants showed size constancy by recovering from habituation when viewing the novel object. Disparity-insensitive infants did not show clear evidence of size constancy. These findings suggest that the development of sensitivity to binocular disparity is accompanied by a substantial increase in the accuracy of infant spatial perception.     

Three- to eight-month-old infants' catching under monocular and binocular vision

We report a cross-sectional and a longitudinal experiment that examined developmental changes in the relative contribution of monocular and binocular variables in the guidance of interceptive arm movements. Three- to eight-month-old infants were observed while presented with differently sized balls that approached frontally with a constant velocity under both monocular and binocular viewing conditions. Movement onset indicated that with age infants increasingly came to rely on binocular variables in controlling the timing of the interceptive arm movements. That is, from 7 to 8 months of age movement onset was independent from object size under binocular but not under monocular viewing. In contrast, binocular viewing enhanced the spatial accuracy of the interceptive arm movements at all ages. We concluded that attunement to binocular information is a key process in infants' gaining adaptive control of goal-directed arm movements. However, interceptive arm movements entail the formation of multiple on-line couplings between optic and movement variables, each of which appears to develop at its own pace.     

Infants’ perception of depth from cast shadows

Five- and 7-month-old infants viewed displays in which cast shadows provided information that two objects were at different distances. The 7-month-olds reached preferentially for the apparently nearer object under monocular-viewing conditions but exhibited no reaching preference under binocularviewing conditions. These results indicate that 7-month-old infants perceive depth on the basis of cast shadows. The 5-month-olds did not reach preferentially for the apparently nearer object and, therefore, exhibited no evidence of sensitivity to cast shadows as depth information. In a second experiment, 5-month-olds reached preferentially for the nearer of two objects that were similar to those used in the first experiment but were positioned at different distances from the infant. This result indicated that 5-month-olds have the motor skills and motivation necessary to exhibit a reaching preference under the conditions of this study. The results are consistent with the hypothesis that depth perception based on cast shadows first appears between 5 and 7 months of age.     

Infants' perception of depth from cast shadows

Five- and 7-month-old infants viewed displays in which cast shadows provided information that two objects were at different distances. The 7-month-olds reached preferentially for the apparently nearer object under monocular-viewing conditions but exhibited no reaching preference under binocular-viewing conditions. These results indicate that 7-month-old infants perceive depth on the basis of cast shadows. The 5-month-olds did not reach preferentially for the apparently nearer object and, therefore, exhibited no evidence of sensitivity to cast shadows as depth information. In a second experiment, 5-month-olds reached preferentially for the nearer of two objects that were similar to those used in the first experiment but were positioned at different distances from the infant. This result indicated that 5-month-olds have the motor skills and motivation necessary to exhibit a reaching preference under the conditions of this study. The results are consistent with the hypothesis that depth perception based on cast shadows first appears between 5 and 7 months of age.     

Infants' responsiveness to line junctions in curved objects

Several empirical studies demonstrate that infants under 6-7 months of age are unable to extract static-monocular depth information from their environment. The aim of this study was to extend these findings by using a three-dimensional structure indicated by curved Y junctions. Infants 5 and 8 months of age were habituated to the line drawing of a cylinder. During test trials, the infants viewed two displays, one in which a surface marking had been deleted from the habituation figure and one in which an edge had been erased. An ANOVA revealed that the 8-month-old subjects looked significantly longer at the dishabituation display lacking the edge, whereas the 5-month-olds did not. The results provide evidence that 8-month-old infants distinguish between lines indicating edges and lines indicating markings and that they are able to use line junctions to perceive line drawings as depictions of three-dimensional objects in the picture plane.     

Infants’ sensitivity to familiar size: The effect of memory on spatial perception

Two experiments investigated infants’ sensitivity to familiar size as information for the distances of objects with which they had had only brief experience. Each experiment had two phases: a familiarization phase and a test phase. During the familiarization phase, the infant played with a pair of different-sized objects for 10 min. During the test phase, a pair of objects, identical to those seen in the familiarization phase but now equal in size, were presented to the infant at a fixed distance under monocular or binocular viewing conditions. In the test phase of Experiment 1, 7-month-old infants viewing the objects monocularly showed a significant preference to reach for the object that resembled the smaller object in the familiarization phase. Seven-month-old infants in the binocular viewing condition reached equally to the two test phase objects. These results indicate that, in the monocular condition, the 7-month-olds used knowledge about the objects’ sizes, acquired during the familiarization phase, to perceive distance from the test objects’ visual angles, and that they reached preferentially for the apparently nearer object. The lack of a reaching preference in the binocular condition rules out interpretations of the results not based on the objects’ perceived distances. The results, therefore, indicate that 7-month-old infants can use memory to mediate spatial perception. The implications of this finding for the debate between direct and indirect theories of visual perception are discussed. In the test phase of Experiment 2,5-month-old infants viewing the objects monocularly showed no reaching preference. These infants, therefore, showed no evidence of sensitivity to familiar size as distance information.     

Sensitivity of 5- and 7-month-old infants to pictorial depth information

An Ames (1951, Psychological Monographs, 65(1, Whole No. 324)) static trapezoidal window, under monocular view, was used to test young infants' responsiveness to pictorial depth. When adults view this display monocularly with the smaller side of the window rotated toward them, they report that the orientation of the display becomes ambiguous: When the head is moved, the window may appear to be in the fronto-parallel plane or either side may appear closer. The 7-month-olds we tested appeared to experience a similar ambiguity; they reached to the near side of the rotated trapezoidal window with significantly less consistency or directedness than infants in a control group tested with a rotated object that lacked pictorial depth information. When 5-month-olds were tested, however, they reached with equal consistency to the closer side of the trapezoidal window and of the control display, apparently uninfluenced by the pictorial depth information available in the trapezoidal window. Thus, sensitivity to the pictorial information for depth that is present in the trapezoidal window appears to develop after the age of 22 weeks.     

INFANT MACAQUE MONKEYS RESPOND TO PICTORIAL DEPTH

Abstract— The studies described here are the first to demonstrate that a nonhuman primate species is capable of responding to pictorial depth information during infancy. In two experiments, pigtailed macaque (Macaca nemestrina) infants were tested for responsivity to the pictorial depth cites of texture gradient/linear perspective and relative size. The procedures were adapted from human studies and are based on the proclivity of infants to reach more frequently to closer objects than to objects that are farther away. The stimulus displays included two equidistant objects that, when viewed monocularly, appear separated in space because of an illusion created by pictorial depth cues. When presented with these displays, animals reached significantly more often to the apparently closer objects under monocular conditions than under binocular conditions. These findings suggest that infant macaques are sensitive to pictorial depth information, the implication being that this ability has ancient phytogenetic origins and ix not learned from exposure to the conventions of Western art.     

Sensitivity to binocular depth information in infants

In order to study infants' sensitivity to binocular information for depth, 11 infants, 20 to 26 weeks of age, were presented with real and stereoscopically projected virtual objects at three distances, and the infants' reaching behavior was videotaped. When the virtual object was positioned out of reach, infants tended to lean further forward and to reach less frequently than when the virtual object was positioned within reach. In addition, the proportion of reaches in which the infants patted, closed their hands, or brought their hands together was greater when the virtual object was within reach. However, no difference in the terminal location of the infants' reaches was found as a function of the virtual object's position. Examination of reaches to a near real object revealed that infants frequently did not contact the object or show appropriate hand shape or orientation. The effectiveness of the cue of retinal size and of binocular information for the depth of an object is discussed. It is concluded that 5-month-old infants are sensitive to binocular information for depth.     

Introduction: A Cognitive Science Slam in Honor of Guy Van Orden

Illusory depth perception experienced in driving simulators is afforded by monocular depth information contained in visual displays. Presumably binocular convergence and binocular disparity, though useful for depth perception in real environments, may poorly contribute to illusory depth in a driving simulator. Instead, they may generate conflicting information by revealing the distance of the display screen and its flatness. Nevertheless, illusory depth induced by monocular information contained in visual displays usually produces enough immersion and realism to create the illusion of driving in a real environment.

Many authors have noted improved depth perception in paintings, photographs, and even in drawings when viewed monocularly. However, this effect, known as monocular advantage, has never been explored in driving simulation. The purpose of this experiment was to assess whether the effect might exist in driving simulation. It was expected that drivers would perceive distances in depth better and more accurately with a monocular than with a binocular viewing of the display. Distance estimates were evaluated for two types of driving maneuvers referred to as alignment and bisection. Results showed that when significant performance differences between monocular and binocular viewing conditions occurred, target cars were perceived farther in depth and more accurately using monocular vision.

Alternative viewing conditions using both eyes are discussed at the end of the article.     

Infants' perception of pictorially specified interposition

Five- and seven-month-olds were tested for sensitivity to pictorial interposition in two experiments. Reaching was used as the dependent measure. Seven-month-olds gave evidence of sensitivity to pictorial interposition. In both experiments they showed a significant preference to reach for the pictorially nearer side of a flat interposition display which stimulated three overlapping surfaces and showed no reaching preferences when viewing control displays. Five-month-olds' reaching tendencies did not differ significantly between experimental (interposition) and control conditions in the second experiment. This result indicated that their responses may have been due to nonspatial proximal stimulus variables in the displays. Five-month-olds, therefore, gave no evidence of sensitivity to pictorial interposition. The finding that 7-month-olds are sensitive to pictorial interposition and the failure to find sensitivity in 5-month-olds is consistent with findings from other studies on infants' sensitivity to pictorial depth information. The cumulative results of these studies suggest that sensitivity to pictorial depth information first appears between 5 and 7 months of age.     

Combining binocular and monocular curvature features.

A study is reported of the perception of visual surfaces in wire-frame stimuli generated by combinations of monocular surface contours and binocular disparity that provide differing information about 3-D relief. Observers vary considerably in the relative contribution made by the binocular and monocular cues to the perception of overall 3-D form. Without training, many observers may entirely fail to perceive surface curvature from the binocular disparity patterns, interpreting the form of the surface only according to the monocular information. For other observers, both cues contribute to the end percept, with the monocular interpretation dominating where the disparity information indicates planarity and with disparity dominating where disparity information suggests curvature and the monocular interpretation suggests planarity. Where stereo and monocular interpretations indicate inconsistent surface curvature features at a common location, more complex resolution strategies are suggested.     

The ground is dominant in infants’ perception of relative distance

When making relative distance judgments, adults attend to information provided by the ground surface and generally ignore information provided by ceiling surfaces. In the present study, we asked whether this ground dominance effect is present in infancy. Groups of 5- and 7-month-old infants viewed a display depicting textured ground and ceiling surfaces. Two toys, which were attached to vertical rods, were affixed to the display. The toys/rods were positioned so that one toy was specified as being nearer by the ground surface but farther away by the ceiling surface, while the other toy was specified as being farther away by the ground surface but nearer by the ceiling surface. Under monocular viewing conditions, the infants in both age groups reached preferentially for the toy that was specified as being nearer by the ground surface. This effect was significantly stronger than that observed under binocular viewing conditions. The findings indicate that the infants responded to the distance information provided by the ground surface to a greater extent than to information provided by the ceiling.     

Children’s sensitivity to pictorial depth information

Children, ranging in age from 3 years, 4 months to 5 years, 4 months, were tested for sensitivity to interposition, height in field, linear perspective, and retinal size under either restricted (monocular, head motionless) or unrestricted (binocular, head free) picture surface viewing conditions. All of the subjects’ relative depth responses (near vs. far) to two toy houses were remarkably accurate with interposition and or height in field pictorial depth information. Retinal size had relatively little control over their responses, and the addition of linear perspective resulted in no significant improvement. Performance was nearly equivalent under the two viewing conditions, indicating young children’s ability to take a “pictorial attitude.”     

Infants’ responsiveness to pictorial depth cues in preferential-reaching studies: A meta-analysis

The findings of numerous preferential-reaching studies suggest that infants first respond to pictorial depth cues between 5 and 7 months of age. However, three recent preferential-reaching studies have found evidence of responsiveness to pictorial depth cues in 5-month-olds. We investigated these apparently contradictory results by conducting meta-analyses of the data from 5-month-olds who participated in preferential-reaching studies. The data from 16 samples, comprising 475 infants 5–5.5 months of age, were integrated. The results showed that the infants responded more consistently to depth relationships specified by pictorial cues under monocular than under binocular viewing conditions (p < .001), indicating that 5-month-old infants respond to pictorial depth cues. This effect remained significant (p < .001) when the individual experiments that had found significant results were omitted from the analysis. Although the majority of experiments were unable to find evidence of pictorial depth perception individually, this ability was clearly revealed when their results were combined.     

Monocular discs in the occlusion zones of binocular surfaces do not have quantitative depth--a comparison with Panum's limiting case

Da Vinci stereopsis is defined as apparent depth seen in a monocular object laterally adjacent to a binocular surface in a position consistent with its occlusion by the other eye. It is widely regarded as a new form of quantitative stereopsis because the depth seen is quantitatively related to the lateral separation of the monocular element and the binocular surface (Nakayama and Shimojo 1990 Vision Research 30 1811-1825). This can be predicted on the basis that the more separated the monocular element is from the surface the greater its minimum depth behind the surface would have to be to account for its monocular occlusion. Supporting evidence, however, has used narrow bars as the monocular elements, raising the possibility that quantitative depth as a function of separation could be attributable to Panum's limiting case (double fusion) rather than to a new form of stereopsis. We compared the depth performance of monocular objects fusible with the edge of the surface in the contralateral eye (lines) and non-fusible objects (disks) and found that, although the fusible objects showed highly quantitative depth, the disks did not, appearing behind the surface to the same degree at all separations from it. These findings indicate that, although there is a crude sense of depth for discrete monocular objects placed in a valid position for uniocular occlusion, depth is not quantitative. They also indicate that Panum's limiting case is not, as has sometimes been claimed, itself a case of da Vinci stereopsis since fusibility is a critical factor for seeing quantitative depth in discrete monocular objects relative to a binocular surface.     

The relative contribution of relative height, linear perspective, and texture gradients to pictorial depth perception in 7-month-old infants

In the current preferential-reaching experiments, 7-month-olds were tested for their ability to respond to a combination of relative height and texture gradients. The infants were presented with a display in which these pictorial depth cues specified that two toys were at different distances. The experimental displays differed from the textured surfaces employed in earlier studies in that linear perspective of the contours of the texture elements was omitted. Experiment A shows that the infants still preferred to reach for the apparently nearer toy under monocular, but not binocular, viewing conditions, indicating that they responded to the pictorial depth cues. In experiment B, relative height and texture provided the infants with conflicting information for depth. Here, relative height outperformed texture information. A statistical comparison between the experiments as well as systematic comparisons with experimental conditions from an earlier study (Hemker et al, 2010 Infancy 15 6-27) revealed that texture gradients, unlike linear perspective, neither enhanced nor weakened the effect exerted by relative height. In sum, 7-month-old infants are obviously more sensitive to relative height and to the linear perspective of the surface contours than to the texture gradients of compression, perspective, and density.