Crawling-onset age predicts visual cliff avoidance in infants

Two experiments are reported that tested the effects of crawling-onset age, the amount of crawling experience, and testing age on avoidance of the deep side of a visual cliff apparatus by human infants. In Experiment 1, 49 infants ranging in age from 7 to 13 mo. were tested on the visual cliff after 1 or 2 mo. of crawling experience. Discriminant analysis revealed that crawling-onset age, and not crawling experience, discriminated between those infants who crossed and those infants who avoided the apparent drop-off. Infants who crossed the deep side were infants with an early crawling-onset age. In Experiment 2, 40 infants were tested on a visual cliff apparatus, half at 9 and half at 12 mo. of age. Discriminant analysis again found that crawling-onset age discriminated between infants who crossed the infants who would not cross the deep side, whereas testing age alone did not. These results call into question the idea that experience crawling is critical in inducing visually guided avoidance behavior in infants. It is argued that the crawling-onset age effect occurs because crawling during the tactile phase of infancy interferes with later visual control of locomotion.     

The visual cliff: cardiac and behavioral responses on the deep and shallow sides at five and nine months of age

Cardiac and behavioral reactions of 5- and 9-month-old infants placed directly atop the two sides of the visual cliff were studied. Evidence of a developmental shift in infant responses on the deep side of the cliff was obtained in heart rate, which shifted from the deceleration previously obtained with younger subjects, to the acceleration obtained with the 9-month-olds of the present study. Behaviorally, visual attention on the two sides was similar at 5 months, but differed at 9 months, being significantly greater on the deep side. Limb movement showed less of an increase on the deep side than on the shallow at both ages tested. Negative vocalization and positive vocalization recordings failed to show any significant effects. The cardiac data are interpreted as indicating a possible shift from attentiveness to fearfulness on the deep side with age.     

Depth perception in Mongolian gerbils (Meriones unguiculatus) and spiny mice (Acomys russatus and A. cahirinus)

Depth perception in gerbils and spiny mice was studied with a modified visual cliff which varied the height of a platform from 5.08 cm to 25.4 cm and presented animals with an apparent drop-off to a patterned or a white field. Time to descend from the platform and orienting response frequency were recorded. For gerbils neither measure varied significantly between the platforms. Both Acomys species increased descent time and orienting response frequency as platform height increased. The results suggest that both gerbils and spiny mice can perceive depth, though there appears to be a difference between the species' use of sensory cues in descending from a visual cliff. The spiny mice appear to rely more on visual cues than do the gerbils. The data also reveal subtle behavioral differences between the Acomys species that may relate to their successful sympatry. The results are discussed by alluding to ecological differences between these species in their natural habitats.     

Nature and nurture in own-race face processing

A standard visual preference task was used to examine 3-month-olds' looking times at own-race versus other-race faces as a function of environmental exposure to faces from the two categories. Participants were Caucasian infants living in a Caucasian environment, African infants living in an African environment, and African infants living in a predominantly Caucasian environment. The results indicate that preference for own-race faces is present as early as 3 months of age, but that this preference results from exposure to the prototypical facial environment.     

The effects of cross-fostering on the development of social preferences in meadow voles (Microtus pennsylvanicus)

To determine the role of the parental environment in the formation of species attachments in the meadow vole (Microtus pennsylvanicus), young of this species were fostered to either meadow vole parents (in-fostered young) or to prairie vole parents (M. ochrogaster; cross-fostered young). At 50 to 60 days of age, subjects were tested for social preference in an environment that simulated the conditions of a runway system. The testing design assessed the reaction of fostered animals to a novel species (M. pinetorum) as well as to the parental and biological species. The proportion of total test time spent near stimulus animals did not vary as a function of rearing condition. However, when compared to in-fostered controls, cross-fostered meadow voles displayed increased preference for prairie voles. Novelty did not appear to be a significant factor in test animal choice. These results suggest that in meadow voles, preference for the species of social partner is dependent on postnatal experience with parents.     

Fathers' versus mothers' social referencing signals in relation to infant anxiety and avoidance: a visual cliff experiment

Infants use signals from others to guide their behavior when confronted with novel situations, a process called ‘social referencing’ (SR). Via SR, signs of parental anxiety can lead to infant anxiety. Little is known about differences in the effect of paternal and maternal SR signals on child anxiety. Using a visual cliff paradigm, we studied whether SR processes between fathers and their infants differed from mothers and their infants. Eighty‐one infants aged 10–15 months were randomly assigned to conduct the visual cliff task with their father (n = 41) or mother (n = 40). The infant was placed on the shallow side of the cliff and the parent, standing at the deep side, was instructed to encourage the infant to cross. Results showed that although mothers showed more intense facial expressions of encouragement than fathers, no differences occurred in how fast, and with how much anxiety, infants crossed the cliff with fathers and mothers. However, path analyses showed that paternal, but not maternal, expressed anxiety was positively associated with infant expressed anxiety and avoidance. For infants who participated with their mother, infants' anxious temperament was negatively associated with infant avoidance of the cliff. Infant anxious temperament moderated the link between paternal expressed anxiety and infant avoidance: the higher the level of infant anxious temperament the stronger the positive association between paternal expressed anxiety and infant's avoidance of the cliff. Lastly, parental encouragement was unrelated to infant expressed anxiety and avoidance. Our results suggest that SR processes between fathers and their infants differ from those between mothers and their infants.     

The development of olfactory preferences for artificial odors briefly experienced by the precocial spiny mouse young

Groups of pups, aged 2, 4, 6, 12, 16, and 18 days of the precocial murid rodent spiny mouse (Acomys cahirinus), were each exposed for 1.5 h to one of the experimental odors, cinnamon or cumin, present in the surrounding environment. The odors were not contingent upon home-cage odors or any other reinforcers. This simple exposure produced a strong preference for the exposed odor in multichoice preference tests carried out 48 h after the exposure in pups from groups aged 2 through 16 days. Older pups exposed to cinnamon or cumin at Day 18 did not show a significant preference for the familiar odor. Both experimental odors used were found to be neutral for control experimentally naive pups within a tested age span. These results point at a stimulus familiarity, rather than associative learning in the development of olfactory preferences in young spiny mouse pups.     

Comparing statistical learning across perceptual modalities in infancy: An investigation of underlying learning mechanism(s)

Statistical learning (SL), sensitivity to probabilistic regularities in sensory input, has been widely implicated in cognitive and perceptual development. Little is known, however, about the underlying mechanisms of SL and whether they undergo developmental change. One way to approach these questions is to compare SL across perceptual modalities. While a decade of research has compared auditory and visual SL in adults, we present the first direct comparison of visual and auditory SL in infants (8–10 months). Learning was evidenced in both perceptual modalities but with opposite directions of preference: Infants in the auditory condition displayed a novelty preference, while infants in the visual condition showed a familiarity preference. Interpreting these results within the Hunter and Ames model (1988), where familiarity preferences reflect a weaker stage of encoding than novelty preferences, we conclude that there is weaker learning in the visual modality than the auditory modality for this age. In addition, we found evidence of different developmental trajectories across modalities: Auditory SL increased while visual SL did not change for this age range. The results suggest that SL is not an abstract, amodal ability; for the types of stimuli and statistics tested, we find that auditory SL precedes the development of visual SL and is consistent with recent work comparing SL across modalities in older children.     

THE VISUAL CLIFF'S FORGOTTEN MENAGERIE: RATS,GOATS, BABIES,AND MYTH‐MAKING IN THE HISTORY OF PSYCHOLOGY

Eleanor Gibson and Richard Walk's famous visual cliff experiment is one of psychology's classic studies, included in most introductory textbooks. Yet the famous version which centers on babies is actually a simplification, the result of disciplinary myth‐making. In fact the visual cliff's first subjects were rats, and a wide range of animals were tested on the cliff, including chicks, turtles, lambs, kid goats, pigs, kittens, dogs, and monkeys. The visual cliff experiment was more accurately a series of experiments, employing varying methods and a changing apparatus, modified to test different species. This paper focuses on the initial, nonhuman subjects of the visual cliff, resituating the study in its original experimental logic, connecting it to the history of comparative psychology, Gibson's interest in comparative psychology, as well as gender‐based discrimination. Recovering the visual cliff's forgotten menagerie helps to counter the romanticization of experimentation by focusing on the role of extrascientific factors, chance, complexity, and uncertainty in the experimental process.     

Figural preference and the visual field

Three experiments tested a hypothesis that the shape and relative dimensions of the binocular visual field determine a preference for rectangles possessing dimensions similar to those of the golden section. The results were that Ss horizontally oriented the rectangles they had drawn in correspondence with the shape of the binocular visual field but when Ss chose the most pleasing rectangles there was no significant preference for rectangles whose long side was horizontal. For all experiments there was little preference for rectangles whose ratio of short to long side approximated the golden section. There was some evidence that the placement of the rectangles with respect to the background affects preference.     

Behavioural characteristics of adolescence in young captive european rabbits,oryctolagus cuniculus

The territoriality of young, wild-type European rabbits, Oryctolagus cuniculus was studied in the laboratory. The experimental procedure was to introduce a strange animal into the pen (“home”) of another rabbit and to record the occurrence of the following forms of behaviour: approach, sniffing, following and chasing, aggression. Altogether 290 rabbits of the following age classes were used - 16 to 30, 31 to 60, 61 to 90, and 91 to 120 days old, and adult females and males The young rabbits were members of 62 separate litters Thirty tests were carried out for each of 21 age-class combinations giving a total of 630 separate tests each lasting 10 minutes. The data collected were subjected to statistical analysis using a multivariate parametric approach to paired comparisons The multiple discriminant analysis was used. The results indicated the preparedness of even the youngest rabbits to defend their own territory and the inhibiting effect of strange territory on all rabbits, except the 61–90-day-old subjects referred to as adolescents. The adolescents displayed aggression to younger as well as older rabbits. Within their own age group even a few days seniority of the introduced individual levelled the intensity of aggression of contestants. This behavioural characteristic was not present in the oldest age class (91–120 days old). The results are discussed in relation to information on the behaviour of free-living rabbits. The innate nature of territoriality of the species is emphasised.     

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.     

Japanese monkeys' cardiac responses to visual depth

The present study examined the heart-rate changes which occurred in the visual-depth situation of Japanese monkeys (Macaca fuscata). Four animals were tested over the first four weeks of age in the visual pitfall designed as a modification of the visual cliff. The infant monkeys showed heart-rate reduction in the depth condition. This reduction was observed from the first week and became remarkable at the third week. There were no differences in heart-rate change between monocular and binocular vision. These findings suggest that the Japanese monkey can discriminate visual depth shortly after birth and that the heart-rate reduction depends upon the fear of visual depth, not upon the novelty of the situation.     

Preference for consonance over dissonance by hearing newborns of deaf parents and of hearing parents

Behavioral preferences for consonance over dissonance were tested in hearing infants of deaf parents and in hearing infants of hearing parents when they were 2 days old. Using a modified visual-fixation-based, auditory-preference procedure, I found that both 2-day-old infants of deaf parents and those of hearing parents looked longer at a visual stimulus when looking produced the original version of a Mozart minuet as opposed to a version altered to contain many dissonant intervals. The relative magnitude of such preference did not significantly differ whether their parents were deaf or hearing. Infants prefer consonance over dissonance, and the preference is present from birth and is not dependent on any specific prenatal or early postnatal experience.     

The development of spatial location coding: Place learning and dead reckoning in the second and third years

There are two possible ways to code spatial location: viewer-referenced and externally referenced systems. The mature form of each system makes use of metric information (in forms of coding termed dead reckoning and place learning, respectively). Each system also exists in a simpler form not using metric information (termed response learning and cue learning, respectively). We report an experiment designed to examine the development of the two mature forms of spatial coding. Children aged 16 to 36 months were asked to search for objects hidden in a long rectangular sandbox, after they moved to the opposite side of the box, either with visual landmarks available or in a curtained environment. When moving in a curtained environment, and hence needing to rely primarily on dead reckoning, children across this age range performed at levels above chance but reliably less accurate than when they did not move. The size of the decrement due to movement did not decrease with age. Thus, the dead reckoning system may become available before 16 months but undergo no further improvement through 3 years. On the other hand, comparisons between children who moved in the curtained environment and children who moved with visual landmarks available showed that only children older than 21 months did better when external landmarks could be seen. This finding suggests a relatively late emergence of place learning.     

Shift of visual field preference for English words in native Hebrew speakers.

Lateralization for visual verbal material was tested with Hebrew and English stimuli presented to Israeli adolescents in their second, fourth, and sixth years of study of English as a second language. Seventy-two children, 12 male and 12 female subjects in each class, were tested by means of a target-word recognition task. Laterality scores derived from reaction-time measures resulted in: (1) a left visual field preference for the English stimuli in the youngest group which decreased with increasing age, becoming a right visual field preference in the oldest group, and (2) a significant and equal right visual field preference for Hebrew stimuli for all groups. The data suggest right hemisphere involvement in acquiring the reading skills of a new language.     

Infants’ recognition of objects using canonical color

We explored infants’ ability to recognize the canonical colors of daily objects, including two color-specific objects (human face and fruit) and a non-color-specific object (flower), by using a preferential looking technique. A total of 58 infants between 5 and 8 months of age were tested with a stimulus composed of two color pictures of an object placed side by side: a correctly colored picture (e.g., red strawberry) and an inappropriately colored picture (e.g., green-blue strawberry). The results showed that, overall, the 6- to 8-month-olds showed preference for the correctly colored pictures for color-specific objects, whereas they did not show preference for the correctly colored pictures for the non-color-specific object. The 5-month-olds showed no significant preference for the correctly colored pictures for all object conditions. These findings imply that the recognition of canonical color for objects emerges at 6 months of age.     

Active vision in passive locomotion: real‐world free viewing in infants and adults

Visual exploration in infants and adults has been studied using two very different paradigms: free viewing of flat screen displays in desk‐mounted eye‐tracking studies and real‐world visual guidance of action in head‐mounted eye‐tracking studies. To test whether classic findings from screen‐based studies generalize to real‐world visual exploration and to compare natural visual exploration in infants and adults, we tested observers in a new paradigm that combines critical aspects of both previous techniques: free viewing during real‐world visual exploration. Mothers and their 9‐month‐old infants wore head‐mounted eye trackers while mothers carried their infants in a forward‐facing infant carrier through a series of indoor hallways. Demands for visual guidance of action were minimal in mothers and absent for infants, so both engaged in free viewing while moving through the environment. Similar to screen‐based studies, during free viewing in the real world low‐level saliency was related to gaze direction. In contrast to screen‐based studies, only infants – not adults – were biased to look at people, participants of both ages did not show a classic center bias, and mothers and infants did not display high levels of inter‐observer consistency. Results indicate that several aspects of visual exploration of a flat screen display do not generalize to visual exploration in the real world.     

The costs of switching attentional sets

People prioritize those aspects of the visual environment that match their attentional set. In the present study, we investigated whether switching from one attentional set to another is associated with a cost. We asked observers to sequentially saccade toward two color-defined targets, one on the left side of the display, the other on the right, each among a set of heterogeneously colored distractors. The targets were of the same color (no attentional set switch required) or of different colors (switch of attentional sets necessary), with each color consistently tied to a side, to allow observers to maximally prepare for the switch. We found that saccades were less accurate and slower in the switch condition than in the no-switch condition. Furthermore, whenever one of the distractors had the color associated with the other attentional set, a substantial proportion of saccades did not end on the target, but on this distractor. A time course analysis revealed that this distractor preference turned into a target preference after about 250-300 ms, suggesting that this is the time required to switch attentional sets.     

Post-retrieval beta-adrenergic receptor blockade: effects on extinction and reconsolidation of cocaine-cue memories

Contexts and discrete cues associated with drug-taking are often responsible for relapse among addicts. Animal models have shown that interference with the reconsolidation of drug-cue memories can reduce seeking of drugs or drug-paired stimuli. One such model is conditioned place preference (CPP) in which an animal is trained to associate a particular environment with the rewarding effects of a drug. Previous work from this laboratory has shown that intra-nucleus accumbens core infusions of a MEK inhibitor can interfere with reconsolidation of these drug-cue memories. A question that remains is whether post-retrieval drug effects on subsequent memories represent an interference with reconsolidation processes or rather a facilitation of extinction. In this experiment, we explore the effect of post-retrieval injections of propranolol, a beta-adrenergic receptor antagonist, on reconsolidation and extinction of cocaine CPP. After acquisition of cocaine CPP, animals were given post-retrieval propranolol injections once or each day during a protocol of unreinforced preference tests, until the animals showed no preference for the previously cocaine-paired environment. Following a cocaine priming injection, the animals that received daily post-test propranolol injections did not reinstate their preference for the drug-paired side. In contrast, a single post-retrieval propranolol injection followed by multiple days of unreinforced preference tests failed to blunt subsequent cocaine reinstatement of the memory. These data suggest that daily post-retrieval systemic injections of propranolol decrease the conditioned preference by interfering with reconsolidation of the memory for the association between the drug-paired side and the reinforcing effects of the drug, rather than facilitating new extinction learning.