In addition to the ethical considerations, faculties recruiting participants and inventing tasks that grab a child’s attention, cognitive developmental psychologist are facing greater challenges with investigating mental functions and processes that cannot be directly observed. Over the past century researcher’s on infant categorization abilities and the mental processes that lie behind its development was limited. This was due to the lack of adequate methods and technology to address the topic.
However, innovative techniques that are now being employed are allowing researchers to explore a child’s ability to organism the countless tumuli they encompass on a daily basis. This essay aims to assess the new research methods being employed and their contribution towards a deeper understanding surrounding the development of classes, categories, and concepts during infancy. Until the late twentieth century the common believe was that infants lack categorization abilities because they were unable to store information in their memory.
This view has changed after the preferential looking paradigm introduced by Fan (1963) in Ethel ass’s. In his studies on infant visual perception, he discovered that after multiple exposures to identical stimuli, infants’ become habituated and the duration of their gaze towards the stimuli declines. Faint (1963) also noticed that infants tend to look longer when presented with novel stimuli. R-anta (1963) findings provided strong evidence for the possibility of categorization abilities within infants.
Categorization refers to the alignment of object that share common features into classes and categories (Tastes et a’, 2004). Thus, organized and accessible storage of memory is essential for recognizing a stimulus as part of a particular category. In fact, habituation accounted for an infants’ ability to distinguish teens stimuli. Moreover, they have stored a memory of the object that was successfully retrieved and subsequently recognizes as familiar during a later stage in time.
Furthermore, the tendency of novelty preference discovered during Faint (1963) studies has become a basic building block for the development of new methods for investigating an infants development (Tastes et al, 2004). One method based on this tendency is the familiarization/novelty preference method, which has been developed in order to investigate what factors are involved in concept development. The method consists of familiarization/ evolve preference stages. In the familiarization stage, infants are presented with a number of familiarization trials in order to habituate a group of objects that belong to the same category.
Once habituated to a particular category, infants are simultaneously introduced to two unseen objects which include a member of the familiar category and a novel category exemplar. If an infant spends more time looking at the exemplar of a novel category, it is assumed that the infant has formed a category representation within their memory during the familiarization phase (Tastes et al, 2004). The familiarization/novelty preference method is a structured laboratory experimental condition in which the independent variables could be manipulated by the researcher.
For this reason the familiarization/novelty preference method is used not only to investigate the formation of category representation but also to explain the cognitive mechanisms behind it. For example, Younger and Godlier (1988) aimed to identify developmental changes in infants’ categorization abilities and how those memories are stored. In both experiments, infants were familiarized with a series of distorted forms of dot pattern prototypes. Similar studies have found that adults are able to individually memorize exemplars from the same category and distinguish between them effectively (Younger et al, 1988).
Therefore, if infants use the so called “exemplar memory,” when presented with a previously seen distortion during habitation together with a prototype of the same category, then they would treat the prototype as a novel stimuli and spend more time gazing at it. Through the above test condition, Younger and Godlier (1988) have found that depending on the experimental conditions, even infants as young as three months old use exemplar memory to store étagère representations. This suggests that category representation is a result of experimental progress or in other words categories are form through top-up processing (Tastes et a’, 2004)..
In experimental conditions, infants store a limited number of simple stimuli in memory and the exemplar memory model could be an effective way to do so. However, in everyday life infants perceive a myriad of stimuli that are more complex. For that reason, it is hypothesize for the existence of a different memory model called “prototype abstraction. ” Prototype abstraction is seen as an automatic recess in which experience with items that belong to a given category result in the formation of a summary representation (prototype) of all the items observed (Tastes et al, 2004).
This hypothesis could also be examined through the familiarization/novelty preference method. For example, in their study Quinn et al. (1994) chooses to habituate infants to more ecologically valid stimuli such as cats and dogs. In the novelty preference stage participant were presented with new exemplars to both the familiar and the novel category. Presumably, if prototype abstraction was not present in an infant’s desegregations, then they would treat both stimuli in the test condition as novel (Tastes et a’, 2004). Quinn et al. 1994) found that infants habituated to cats and treat dogs as novel during the preference test. Results suggest that infants can form a category for cats, which exclude dogs and they do so through a prototype abstraction memory model. The familiarization/novelty preference method has also been used to investigate whether infants can form more abstract concepts. One such study conducted by Quinn (1994). Suggested he inspected a three month old infants’ ability to categorize spatial relations using dots placed above and low a line. For the purpose of the study, infants were divided into two groups.
Half of them were familiarized with four models demonstrating a horizontal bar with a single dot in different positions above it. The other half of the participants viewed the same set of stimuli but with the dot placed below the line (Tastes et al, 2004). A preference test on both groups used a pair of novel exemplars, one of which had the dot placed in a position used during habituation and another in the novel opposite spatial position. As a result Quinn (1994) observed that infants show preference toward the novel sections of the dot, which suggested that they had formed a category representation for above and below (Tastes et al, 2004).
The familiarization/novelty preference method appears to be a useful measure of an infants cognitive development. However, it has been criticized for the lack of ecological validity due to the use of static two- dimensional images, which are not common in one’s everyday experience (Tastes et al, 2004). Other procedures with more realistic objects have been developed in order to address the above issue. For example, the sequential touching procedure involves infants being given an object-manipulation task in which a particular category contrast is tested.
Toys representing different categories in real- world objects are randomly placed in front of the infant. The infant is allowed to manipulate the objects for a set period of time and the order in which objects are touched is recorded. If infants touch the object Of one category before the other, it is assumed that categorization has taken place. This technique is used to determine the information used by infants during categorization (Tastes et alarm 2004). Within adults, categorization is a summary of concepts about an object insisting of both perceptual and conceptual attributes.
Perceptual attributes are associated with the visual features of an object size, shape, sound, and motion patterns. In contrast, conceptual attributes are not visible and require a level of experience and knowledge about the objects function and associated abstract information (Mandrel, 2000). However, young infants have not yet had the experience to acquire such knowledge about an object’s conceptual characteristics. Hence, they must rely on perceptual information when grouping things into categories (Tastes et al, 2004). As previously mentioned, exemplar memory is efficient only when there is limited number of stimuli.
In following this logic, one can conclude that it is not possible for an infant to remember each object’s perceptual features. Therefore, some perceptual information should be a cue when infants are grouping object into categories. Using a sequential touching procedure Arkansan and Buttonholer (1998) studied fourteen, twenty two month old infants, and set out to examine what perceptual cues they use to categorically discern animals from vehicles. In the experiment, infants were given toy objects covering basic car and vehicle disgorges.
Testing was comprised of normal category exemplars as well as modified versions of the exemplars with missing legs and wheels (Rakings et al, 1998) . The analysis of this study showed that infants only distinguish between normal category exemplars, but sequential touching was not observed with the modified versions. This result suggested that infants are able to for global level categories with the use of specific perceptual features (Rakings et al, 1998). A further investigation into the perceptual features used in an infant’s categorization pays attention to dynamic movement cues.
For example, Ratepayers and Bernstein (2002) were interested in the role that dynamic movement cues play in animal and vehicle categorization. A sequential touching procedure was conducted by presenting toy objects of animals and vehicles to three, six and nine month old infants. However, in contrast with the above experiment, dynamic point light displays were attached to the models. Results showed that infants can categorize animal and vehicle on the basis of their movement (Tastes et al, 2004). Ratepayers and Bernstein (2002) also found that nine months old infants transferred these category presentations into static objects.
Moreover, these results provide evidence for bottom-down processing (categorizing through experience) due to an increased mobility in older infants (Tastes et al, 2004). Progression with age from top-up to bottom-down processing suggests a developmental trend towards complexity and the formation Of mature adult concepts. While the familiarization/novelty preference method can measure global level categorization, other research methods designed to test older infants have provided evidence for their ability to form different levels of category representations(Tastes et al, 2004).
For example, an object examination method counts on realistic three-dimensional stimuli to test categorization in infants that are over seven months old. The experiment consisted of a fixed duration familiarization trial, in which infants are allowed to manipulate different toy exemplars from the same category that are presented in a random order with a test phase similar to the familiarization/ novelty preference method. Duration of active examination between novel instance from a familiar category, a novel instance from a category or a completely novel stimulus is measured to infer categorization.
In this procedure a careful manipulation Of the stimuli is presented to the infant and researchers are able to examine the infant’s ability to categorize on both a basic and specific level (Tastes et al, 2004). The research methods mentioned above are innovative techniques scientifically applied to develop theories on infants’ cognitive development. Nevertheless, it is worth acknowledging that each technique has advantages and limitations.
First, as a laboratory experiment the familiarization/novelty preference method allows researchers to manipulate independent variables ender controlled conditions and can be used to study infants at very early age. However, the main limitation as in most laboratory experiments is the lack of ecological validity. Infants are placed in an unfamiliar situation and presented with artificial stimuli (Tastes et al, 2004). In contrast, the sequential touching procedure and object examination method do not lack ecological validity.
In fact, they observe a child’s behavior towards realistic three-dimensional stimuli such as toys that are already part of an infants real life experiences. The main limitation is that they are unsuitable for very young infants that lack the ability to manipulate toys. In addition, the results from this kind of experiment are difficult to analyses and could be incorrectly interpreted (Houston-Price et a’, 2004). In a conclusion, it appears that the process of conceptual formation follows developmental trends from simple to complex.
There is also some support for movement from a global to a specific level of category representation with age. Researchers have found a presence of adult like memory processes such as exemplar memory and prototype abstraction in an infants categorization. Furthermore, research has proven that an infants remarkable ability to use perceptual information when grouping objects into categories, and regardless of each research methods limitations, research has provided valuable insight into an infants’ cognition, pushing forward the boundaries of developmental psychology.