A test of color constancy in 4-month-old human infants

Forty-five 4-month-old infants were tested for color constancy using a familiarization, paired-comparison paradigm. Infants were familiarized and tested with colored stimuli under two conditions: (1) no change in the illuminant between familiarization and test and (2) a change in the illuminant between familiarization and test. Infants correctly recognized the familiarization color when tested with no change in the illuminant. Infants tested with a change in the illuminant correctly recognized the familiar color under some conditions yet failed to do so under others. Several explanations are considered for these results and it is concluded that color constancy operates immaturely at 4 months of age.     

Long-term retention in 3.5-month-olds: familiarization time and individual differences in attentional style

Using a paired-comparison procedure, we examined the effect of familiarization variables on 3.5-month-old infants' (n = 120) retention of dynamic visual stimuli after 1-min, 1-day, and 1-month delays. The proportion of total looking time to the novel stimulus revealed novelty, null, and familiarity preferences after 1-min, 1-day, and 1-month delays, respectively, for infants who were permitted 30 s of familiarization time. Twenty seconds of familiarization time was insufficient to produce novelty preferences. These results support models of infant retention in which the direction of attentional preferences (novel, familiar, or null) depends on memory accessibility. To examine the impact of individual differences in familiarization or attentional style on memory, infants were identified as long or short lookers according to their peak-look duration on pretest and familiarization trial measures. Compared to long lookers, short lookers showed better retention over time indicating that much of the variability in the infant group data could be accounted for by these individual differences.     

Categorization in infancy based on novelty and co-occurrence

Abstract categories (i.e., groups of objects that do not share perceptual features, such as food) abound in everyday situations. The present looking time study investigated whether infants are able to distinguish between two abstract categories (food and toys), and how this ability may extend beyond perceived information by manipulating object familiarity in several ways. Test trials displayed 1) the exact familiarized objects paired as they were during familiarization, 2) a cross-pairing of these same familiar objects, 3) novel objects in the same category as the familiarized items, or 4) novel objects in a different category. Compared to the most familiar test trial (i.e., Familiar Category, Familiar Objects, Familiar Pairings), infants looked longer to all other test trials. Although there was a linear increase in looking time with increased novelty of the test trials (i.e., Novel Category as the most novel test trial), the looking times did not differ significantly between the Novel Category and Familiar Category, Unfamiliar Objects trials. This study contributes to our understanding of how infants form object categories based on object familiarity, object co-occurrence, and information abstraction.     

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.     

Infants' discrimination of photographs of faces following redundant presentations

Infants' discrimination of photographs of faces, as indicated by fixation toward novel targets, was the criterion used to evaluate familiarization conditions designed to facilitate the exercise of selective attention. Groups of 19- and 23-week-old infants were shown either pictures of different faces of the same sex, differing poses of the same face, or repeated exposures of the face that served as a test stimulus. The older infants demonstrated differential attention to novel over familiar stimuli during subsequent recognition tests, and an examination of their responsiveness during familiarization presentations indicated differing trends of looking activity.     

Visual feature binding in early infancy

How does the developing brain of the human infant solve the feature-binding problem when visual stimuli consisting of multiple colored objects are presented? A habituation--dishabituation procedure revealed that 1-month-old infants have the ability to discriminate changes in the conjunction of a familiar shape and color in two objects. However, this good earlier performance was followed by poorer performance at 2 months of age. The performance improved again at 3 months of age. Detailed analysis of the oculomotor behaviors revealed that the age of 2 months was a period of drastic transition when the tendency to stay with the fixated objects disappeared and repetitive saccades between the two objects emerged. Our findings suggest that the ability to perceive conjunctions of features is available to infants very early, that the perceptual/neural basis at 1 and at 3 months of age may be fundamentally different, and that feature integration by vigorous eye movements or selective attention may be the key functional difference between the age groups.     

The influence of novelty and complexity on exploratory behavior in 12-month-old infants

This study investigated the influence of the novelty of the environment and the novelty and complexity of the objects (toys) it contained on the exploratory behavior of 12-month-old infants. Each infant was given a choice between novel and familiar toys located in two adjacent rooms (toy rooms). The novelty of the objects was manipulated by allowing the infants to play with one set of toys during a 5-min familiarization trial prior to the choice trial. The novetly of the environment was manipulated by allowing some infants to see, enter, and remain in the toy rooms during the familiarization trial. Finally, the complexity of the objects was manipulated by varying the number of familiar and novel toys; some Ss had four toys in each set (complex array) and some had only one (simple array). The results indicate that all three factors influenced the infants' exploratory behavior. Ss first approached, and spent more time manipulating, the novel than the familiar toys; they spent more time in the toy rooms if they were novel; and they spent more time manipulating the complex array of toys than the simple array.     

Six-month-olds’ ability to use linguistic cues when interpreting others’ pointing actions

The present research investigated whether six-month-olds who rarely produce pointing actions can detect the object-directedness and communicative function of others’ pointing actions when linguistic information is provided. In Experiment 1, infants were randomly assigned to either a novel-word or emotional-vocalization condition. They were first familiarized with an event in which an actor uttered either a novel label (novel-word condition) or exclamatory expression (emotional-vocalization condition) and then pointed to one of two objects. Next, the positions of the objects were switched. During test trials, each infant watched the new-referent event where the actor pointed to the object to which the actor had not pointed before or the old-referent event where the actor pointed to the old object in its new location. Infants in the novel-word condition looked reliably longer at the new-referent event than at the old-referent event, suggesting that they encoded the object-directedness of the actor’s point. In contrast, infants in the emotional-vocalization condition showed roughly equal looking times to the two events. To further examine infants’ understanding of the communicative aspect of an actor’s point using a different communicative context, Experiment 2 used an identical procedure to the novel-word condition in Experiment 1, except there was only one object present during the familiarization trials. When the familiarization trials did not include a contrasting object, we found that the communicative intention of the actor’s point could be ambiguous. The infants showed roughly equal looking times during the two test events. The current research suggests that six-month-olds understand the object-directedness and communicative intention of others’ pointing when presented with a label, but not when presented with an emotional non-speech vocalization.     

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.     

Recognition memory and cardiac vagal tone in 6-month-old infants

Individual differences in visual recognition memory and cardiac vagal tone were assessed in 14 6-month-old infants. A multi-dimensional problem was presented with the paired-comparison technique to assess recognition memory. Cardiac vagal tone was evaluated by quantifying the amplitude of respiratory sinus arrhythmia. Individual differences in spontaneous baseline cardiac vagal tone were correlated with two measures of visual recognition memory. Infants characterized by high cardiac vagal tone looked for shorter periods at the standard (i.e., familiar) stimulus during familiarization and looked for longer periods at the novel stimulus during the test trials. In response to the visual stimulus during the familiarization and test trials, heart rate decelerated only for the infants who performed well on the visual recognition memory task (i.e., those who looked longer at the novel stimulus than the familiar stimulus).     

Relational memory during infancy: evidence from eye tracking

Here we report evidence from a new eye‐tracking measure of relational memory that suggests that 9‐month‐old infants can encode memories in terms of the relations among items, a function putatively subserved by the hippocampus. Infants learned about the association between faces that were superimposed on unique scenic backgrounds. During test trials, infants were shown three faces presented on a familiar scene. All three faces were equally familiar; however, one had been presented with the test background earlier. Visual behavior was recorded continuously using a TOBII eye tracker. Infants looked preferentially at the face that matched the test background very early in the trial; however, the time course of this preferential looking effect varied as a function of delay. These results suggest that by 9 months of age infants can form memories that represent the relations among items and maintain them over short delays.     

Visual processing of stimulus compounds in newborn infants

An experiment is described in which newborn infants' processing of stimulus compounds was investigated. After familiarization to two alternately presented stimuli which differed in colour and orientation, the newborns showed significant preferences for a stimulus which had a novel colour/orientation combination: the novel stimulus was produced by recombining features of the stimuli used for familiarization. This finding argues against the view that infants initially process separate components, or parts, of visual stimuli and are only able to attend to the correlations between them after about 3 months of age. Rather, the ability to process and remember stimulus compounds is present at birth.     

Infants' sensitivity to differential luminance as information about depth

To what degree are young infants able to perceive differential shadowing and to what degree are they able to utilize this stimulus parameter as information about depth? Two habituation experiments were performed. In Experiment 1, a group of 5-month-old infants were habituated to a low frequency, vertical, and approximately sinusoidal luminance grating superimposed on a flat colored surface. This display induced stable 3-D perception in adult subjects. After habituation, the infants viewed two test displays at alternating trials. One was made up of real half cylinders matching the light distribution of the habituation display and the other was made up of a square wave grating of the same spatial frequency as in the habituation one. Adults perceived the latter display as flat. Results showed that both test displays were treated as new ones by the infants habituated to the sinusoidal grating. Experiment 2 was identical to Experiment 1, except that the subjects were 3 1/2-month-old. These infants treated the half cylinders as familiar and the square wave grating as new. The results indicate that infants at both age levels (3 1/2 and 5 months of age) were sensitive to the difference between sharp and gradual change in luminance which is a prerequisite for perceiving form from luminance. However, neither age group seemed to utilize gradual change in luminance as information about space.     

The cocktail party effect in infants

Most speech research with infants occurs in quiet laboratory rooms with no outside distractions. However, in the real world, speech directed to infants often occurs in the presence of other competing acoustic signals. To learn language, infants need to attend to their caregiver’s speech even under less than ideal listening conditions. We examined 7.5-month-old infants’ abilities to selectively attend to a female talker’s voice when a male voice was talking simultaneously. In three experiments, infants heard a target voice repeating isolated words while a distractor voice spoke fluently at one of three different intensities. Subsequently, infants heard passages produced by the target voice containing either the familiar words or novel words. Infants listened longer to the familiar words when the target voice was 10 dB or 5 dB more intense than the distractor, but not when the two voices were equally intense. In a fourth experiment, the assignment of words and passages to the familiarization and testing phases was reversed so that the passages and distractors were presented simultaneously during familiarization, and the infants were tested on the familiar and unfamiliar isolated words. During familiarization, the passages were 10 dB more intense than the distractors. The results suggest that this may be at the limits of what infants at this age can do in separating two different streams of speech. In conclusion, infants have some capacity to extract information from speech even in the face of a competing acoustic voice.     

Do 9-month-old infants expect distinct words to refer to kinds?

In 3 experiments, 9-month-old infants' expectations for what distinct count noun labels refer to were investigated. In Experiment 1, a box was opened to reveal 2 objects inside during familiarization: either 2 identical objects or 2 different objects. Test trials followed the same procedure, except before the box was opened, the contents were described using 2 distinct labels ("I see a wug! I see a dak!") or the same label twice ("I see a zav! I see a zav!"). Infants who heard a label repeated twice looked longer at 2 different objects versus 2 identical objects, whereas infants who heard 2 distinct labels showed a different pattern of looking. Experiments 2 and 3 presented infants with object pairs that only differed in shape or color, and it was found that infants expected the different-shaped (but not the different-colored) objects to be labeled by distinct count nouns. Because the property of shape is a cue to kind membership and the property of color is not, these results suggest that even at the beginning of word learning, infants may expect distinct labels to refer to distinct kinds of objects.     

Infants' learning,memory, and generalization of learning for bimodal events

Study 1 investigated whether infants 3 and 7 months of age show differential learning of and memory for sight-sound pairs depending on whether or not temporal synchrony was present; memory was assessed after a 10-min and 1-week interval. Study 2 examined whether 7-month-olds show generalization of learning when they encounter novel bimodal events that are similar (changes in size, orientation, or color, and spectral sound properties) to the sight-sound pairs learned 1 week earlier based on temporal synchrony. For Study 1, infants received a familiarization phase followed by a paired-comparison preference procedure to assess for learning of the sight-sound pairs. One week later a memory test was given. Results confirmed that 7-month-olds had no difficulty learning auditory-visual pairings regardless of whether or not events were temporally synchronous, and they remembered these 10 min and 1 week later. In contrast, 3-month-olds showed poorer learning of sight-sound associations in the no-synchrony than synchrony conditions, and memory for sight-sound pairs 1 week later was shown only for the synchrony conditions. Results for Study 2 revealed generalization of learning of bimodal pairings under all stimulus conditions after a 1-week interval at 7 months of age. Implications of these findings for development of intersensory knowledge are discussed.     

Metameric intransitivity

There are two kinds of afterimages. In negative afterimages, looking at a blank field after staring at a colored figure gives a figure whose color is complementary to that of the original figure. Less well understood and studied is the phenomenon of induced positive afterimages, in which staring at a colored area surrounding a small white test patch produces an afterimage in which the hue of the surround is transferred into the previously white area. Using these differences between positive and negative afterimages and also simultaneous color contrast, which has an effect on a test patch different from either of the afterimage effects, we describe a new effect, metameric intransitivity, in which perceptually similar images can generate markedly different afterimages, whereas perceptually different images can generate indistinguishable afterimages. Supplemental figures depicting the stimuli, results, and method for generating the intransitive metamers in this study may be downloaded from http://app.psychonomic-journals.org/content/supplemental.     

When do infants expect hands to be connected to a person?

A violation-of-expectation paradigm was used to test whether infants infer a person based on the presence of hands alone. Infants were familiarized to a pair of hands that extended out from a curtain to play with a rattle, after which the curtain was opened to reveal either a real person or a mannequin. Infants’ looking at these outcomes was compared with baseline looking at the person and the mannequin. Experiment 1 showed that 9-month-olds looked significantly longer at the mannequin than at the person after familiarization to hands. Experiment 2 ruled out a low-level feature matching interpretation by showing the same looking pattern in 9-month-olds even when the hands were covered with silver gloves. In Experiment 3, 6-month-olds showed no differential looking at the mannequin and person after familiarization to hands. Taken together, these experiments suggest that infants acquire the expectation that hands are connected to a person between 6 and 9 months of age. This finding has implications for how infants’ attribute goals to manual actions.     

Across space and time: infants learn from backward and forward visual statistics

This study investigates whether infants are sensitive to backward and forward transitional probabilities within temporal and spatial visual streams. Two groups of 8‐month‐old infants were familiarized with an artificial grammar of shapes, comprising backward and forward base pairs (i.e. two shapes linked by strong backward or forward transitional probability) and part‐pairs (i.e. two shapes with weak transitional probabilities in both directions). One group viewed the continuous visual stream as a temporal sequence, while the other group viewed the same stream as a spatial array. Following familiarization, infants looked longer at test trials containing part‐pairs than base pairs, although they had appeared with equal frequency during familiarization. This pattern of looking time was evident for both forward and backward pairs, in both the temporal and spatial conditions. Further, differences in looking time to part‐pairs that were consistent or inconsistent with the predictive direction of the base pairs (forward or backward) indicated that infants were indeed sensitive to direction when presented with temporal sequences, but not when presented with spatial arrays. These results suggest that visual statistical learning is flexible in infancy and depends on the nature of visual input.     

Twelve‐ to 14‐month‐old infants can predict single‐event probability with large set sizes

Previous research has revealed that infants can reason correctly about single‐event probabilities with small but not large set sizes ( Bonatti, 2008 ; Teglas et al., 2007 ). The current study asks whether infants can make predictions regarding single‐event probability with large set sizes using a novel procedure. Infants completed two trials: A preference trial to determine whether they preferred pink or black lollipops and a test trial where infants saw two jars, one containing mostly pink lollipops and another containing mostly black lollipops. The experimenter removed one occluded lollipop from each jar and placed them in two separate opaque cups. Seventy‐eight percent of infants searched in the cup that contained a lollipop from the jar with a higher proportion of their preferred color object, significantly better than chance. Thus infants can reason about single‐event probabilities with large set sizes in a choice paradigm, and contrary to most findings in the infant literature, the prediction task used here appears a more sensitive measure than the standard looking‐time task.