PropertyValue
is nif:broaderContext of
nif:broaderContext
is schema:hasPart of
schema:isPartOf
nif:isString
  • A total of 106 infants were tested. Infants had no reported birth complications, as well as no visual or auditory impairment. Seventy-nine infants were included in the final analysis (M age = 12.36 months, SD =.42, age range: 11.69 to 13.40 months; 42 males) as the remaining 27 participants were excluded due to fussiness (n = 17), throwing toys (n = 8), and parental interference (n = 2). The experimental procedures were approved by the Human Research Ethics Committee of Concordia University, and all the parents involved were informed and consented (in written form) to let their child participate prior to data collection. All participants were free to withdraw from the experiment at any time. Human Biological Motion Prime. The human point-light walker video was composed of 11 point-light dots placed on all the major joints of the body. The walker moved rightward with no horizontal translation, 20 steps (10 gait cycles). In the creation of the human walker, eleven marker positions were used to capture the subject’s motion at all the major joints of the body. These markers convey important information about both the structure of the body (where the various joints and bones are located) and the dynamic movements of each part (e.g., the velocity of the arm swing vs. the stability of the trunk) [33]. The final video consisted of one 15-second trial, containing 30 complete gait cycles (0.5 seconds/cycle). Schematic Motion Prime. The stimulus presented in this video was adapted from Michotte’s [27] schematic, non-rigid, caterpillar motion. A blue square (1.5 cm x 1.5 cm) expanded towards the right, while the left side remained still, forming the shape of a rectangle (1.5 cm x 3.5 cm). Next, the rectangle contracted wherein the right side remained still and the left side moved until the shape returned to its original form. The overall motion pattern of the schematic form was a rightward horizontal translation. This expansion-contraction motion was repeated six times for a trial duration of 15 seconds. At the beginning of each new trial, the square reappeared on the left side of the screen and moved rightward. Random Motion Control Prime. The random motion control video used the same 11 point-light dots as the human biological motion display. Each dot was given a smooth line of trajectory and a fixed speed using VPixx© software [34]. None of the dots contained animate cues, such as the ability to change direction, change speed, or move contingently with other dots. The direction of the point-light dots was also controlled by having the same amount of dots moving to the right, left, up, or down. Infants were randomly assigned to the human biological motion prime condition (n = 25), the schematic motion condition (n = 28), or the random motion control condition (n = 26). Infants viewed the video prime on a 61 cm x 36 cm screen placed at eye level, approximately 100 cm from the infant. Infants’ gaze was filmed and displayed on a computer monitor. Looking times were coded live using Habit 2000 software [35]. At the beginning of each trial, an attention getter (e.g., moving shape with sound) was used to orient infants’ gaze to the screen. This same stimulus also appeared when the infant looked away for more than two seconds. Each trial was 15 seconds in duration and infants were given a maximum of 14 trials to habituate. Infants were considered habituated once they reached the criterion, defined as three successive trials where the infants’ looking time was less than half of their looking time on the first three trials [36]. Sequential Touching Task. The sequential touching task is an implicit measure of infants’ ability to differentiate categories by measuring infants’ sequence of touches toward an array of toys from contrasting categories. Categorization is typically inferred if the infant touches objects from the same category in sequence before touching objects from the other category [37]. This procedure is considered appropriate for children between the ages of 13 and 30 months [38]. Infants were given a tray of eight toys containing four exemplars from two contrasting categories. The experimenter instructed infants by saying, “Look at all these toys. These toys are for you!” as a sweeping motion was made over the toys. Infants were given the opportunity to explore the toys without constraint for two minutes [39]. If infants dropped a toy on the ground, the experimenter simply placed the toy back on the tray. Two sequential touching trials were administered in counterbalanced order: animal-vehicle and furniture-vehicle. The animal-vehicle tray was comprised of four animals (pig, lion, duck, dolphin) and four vehicles (boat, tractor, car, truck). The furniture-vehicle tray was comprised of four pieces of furniture (grandfather clock, desk, chair, TV stand) and four vehicles (train, sports car, bus, plane). During the testing session, participants were placed in a high chair and their parent sat behind them. Parents were advised to not direct their child’s attention to any toys (e.g., pointing or labeling). After the participants viewed the priming videos, the sequential touching task was administered. Coding and Reliability. The sequences of touches to objects on both trays were coded for each participant. Thus, infants received separate scores for the animal-vehicle and furniture-vehicle trays. A touch was considered only if the infant coordinated touching using his/her hand, finger, or another object with eye gaze toward the object. Therefore, the following behaviors were not counted as a touch: if the infant accidentally touched an object without coordinated gaze or if the infant touched an object immediately after it was placed back on the tray (if dropped). Furthermore, to ensure that the infant was actively associating the objects touched in sequence, a delay between touches of 10 seconds or more was coded as a break in the run. Simultaneous touching of two objects from the same category was considered a single touch, while simultaneous touches of objects from different categories did not constitute a touch. Additionally, infants had to touch at minimum of one toy from each category, and throw fewer than three toys per categorization tray in order to be included. A mean run length (MRL) for each tray of objects was calculated by dividing the total number of touches across categories by the total number of runs (i.e. touches to objects of the same category). The MRL for both trays was compared against chance (1.75). Chance is calculated using a formula that takes into account the total number of categories (2) and objects used (n) in the procedure [37]. A MRL of 1.75 or lower indicates that the infant touched the objects in a random order or in alternation; however, a MRL statistically above 1.75 is interpreted to indicate that infants performed successive touching. It has been argued that successive touching (above chance) reflects infants’ processing of within-category similarity. In contrast, alternating touching (below chance) reflects attention to between-category differences. Successive touching is considered a more advanced form of categorization that emerges later in infancy [40]. Since we predicted that priming would facilitate a mature form of categorization consisting of above chance performance (i.e. statistically greater than 1.75), one-tailed t-tests were used. An independent observer blind to the priming condition coded 25% of the sample to assess inter-rater reliability. A Pearson correlation was computed as r = 0.93 for the human biological motion condition, r =.88 for the schematic motion condition, and r =.93 for the random motion condition. Although MRL analyses are informative to assess the categorical abilities of groups of individuals, this type of analysis tells us little about an individual child’s knowledge of categories, nor of the type of touching that took place. Therefore, an additional approach for analyzing children’s sequential touching was employed. This was to ascertain whether a child’s touches were primarily aimed toward either category or equally toward both categories. As outlined by Dixon, Price, Watkins, and Brink [41], children’s sequential touching was coded for “special” runs, which consist of touching a minimum of three different objects from the same category (either animal or vehicle) in succession. Based on these ‘special runs’, each participant was then classified as a noncategorizer, a single categorizer, or an exhaustive (dual) categorizer. Noncategorizers refer to those participants with no special runs in either category. Single categorizers refer to those participants with at least one special run in only one category (animal or vehicle). Finally, exhaustive categorizers refer to participants with at least one special run in both categories (animal and vehicle). The entire sequence of touches for each participant that contains the special runs was then entered into a Monte Carlo program (TouchStat 3.0) [41] to determine if they were likely to have occurred by chance. The program then simulated 10,000 random touch sequences in order to determine the frequency of occurrence of these special runs. Based on Mandler et al. [37], a probability lower than.10 (p <.10) signified that the participant’s run was unlikely to be due to chance alone. Based on the probability results, we determined whether each participant still qualified for their single categorizer or exhaustive categorizer status. The percentage of participants in each category was then calculated using the results of the Monte Carlo analyses.
rdf:type