Sensation refers to the detection and discrimination of sensory information.
Perception involves the interpretation of those sensations, including recognition and identification.
Comparing Perspectives on Newborn Sensory Experience
John Locke (1690):
In his "Essay Concerning Human Understanding," Locke describes the newborn mind as a white page; all ideas and abilities are developed through learning and experience.
William James (1890):
He posits that the newborn is subject to a "blooming, buzzing confusion," overwhelmed by sensory inputs from all senses at once (eyes, ears, nose, skin, and intestines).
Modern Perspective:
Today, it is recognized that infants are born with numerous innate skills and they perform rapid learning as they engage with their surroundings.
Testing Methods in Vision
Importance of Vision:
Vision is crucial for humans and occupies nearly half of the cerebral cortex.
Infants' Visual Abilities:
Infants are born with relatively well-developed vision that improves significantly during the first months of life.
Testing Paradigms:
Preferential Looking: Assess if an infant can discriminate between two similar visual stimuli by measuring looking time; longer gazes indicate a preference or discrimination.
Habituation: Refers to the gradual decrease in response to a repeated stimulus; if looking time is similar for both stimuli, no preference or discrimination is observed.
Habituation in Infants
Definition of Habituation:
A gradual decrease in interest or response to a repeated stimulus.
Novelty Preference:
Humans show a preference for new or different stimuli.
Experimental Design for Habituation:
Present an infant with a stimulus to gauge initial attention/interest.
Continuously present the same stimulus until attention wanes, indicating habituation.
Introduce a different stimulus; increased attention indicates the infant can distinguish between the two.
Advantages of Habituation:
Infants will prefer a new stimulus regardless of its complexity, accommodating individual differences in the rate of habituation.
Visual Acuity in Infants
Infants can see at birth but lack visual acuity; this can be tested through preferential looking between narrow stripes and a plain field.
Best vision for stationary objects is at a distance of 20-25 cm. Vision rapidly improves within the first month as tracking and scanning abilities develop.
By 6 months, visual acuity reaches near-adult levels.
Color, Patterns, and Contrasts
Initial Color Vision Limitations:
Color vision develops as the retinal cones mature:
By 2-3 months, infants begin to perceive adult-like color categories.
By 4-5 months, they develop adult-like color preferences.
Pattern Recognition:
Requires higher-order cognitive processes; infants visual scanning evolves over time from a focus on single features to more comprehensive tracking of object details.
Development of Preferences:
As infants mature, they prefer more complex patterns, aiding in their understanding of object structure and boundaries.
Changes in Visual Preferences
Fantz (1961, 1963, 1965):
Infants show a preference for patterned surfaces over plain surfaces and favor faces over other patterns.
Reasons for Face Preference:
Faces are three-dimensional, moving, and exhibit high-and-low contrast areas, offering visual and auditory stimulation, which helps in regulating the infant's behavior.
Genetic predisposition?:
Research suggests a potential genetic component in infants' preference for faces (Pascalis & Kelly, 2009).
Subsequent Studies:
Dannemiller & Stephens (1988): Demonstrated a preference for one computer-generated figure over others, indicating an early tendency to favor complex patterns.
Evidence Supporting Preference for Faces
Previous notions indicated an initial general preference for face-like patterns, which later develop into a learned preference for faces. However, evidence suggests the specialness of faces:
Newborns (less than 3 days old) prefer adult female faces deemed attractive rather than non-attractive but similar faces (Slater et al., 2010).
Social Learning:
Increases face preferences within the first month, including a preference for faces of the same sex as their caregiver (Quinn et al., 2002; Slater et al., 2010) and the own-race effect, which emerges around 3 months and solidifies by 9 months.
Preference for Smiling Faces:
By 3 months, infants show a preference for smiling faces.
The Still Face Paradigm
Tronick (1975):
Demonstrated a robust paradigm where infants initially attempt interaction with an expressionless mother but eventually exhibit signs of distress and withdrawal.
Implications for Maternal Depression:
Normal interactions restore joy, highlighting the effect of maternal mood on infant emotional well-being.
Object and Depth Perception
Object Constancy:
The belief or perception that an object remains constant regardless of changes in appearance. This involves innate knowledge of shape constancy and size constancy, vital for maintaining a stable perceptual world.
Research Evidence:
Studies (e.g., Bower, 1965) have indicated the early development of object constancy in infants.
Conditioned Head-Turn Technique
Used for older infants;
Infants receive rewards for turning their head to one side and eventually only when a specific stimulus is presented.
Object Continuity:
Kellman & Spelke (1983) showed 4-month-olds habituated to a rod moving behind a block preferred a broken rod over a whole rod, indicating recognition of parts as part of a complete object.
Depth Perception
3D World Visualization:
Given that our retinas provide 2D images, depth perception requires infants to learn how to perceive distance, which begins to occur at 2-3 months. By 4 years, their perception of depth achieves adult-like proficiency.
Visual Cliff Experiment:
Gibson & Walk (1960); Campos (1970): Found that infants under 6 months are more curious and likely to cross the visual cliff, while 6- to 14-month-olds avoid crossing even with parental coaxing, indicating developed depth perception.
Adult Heart Rate Responses and Infant Development
Heart Rate Deceleration:
Occurs in response to novel or attractive stimuli and interesting but non-exciting stimuli.
Heart Rate Acceleration:
Triggered by potentially dangerous or aversive stimuli or highly stimulating events.
Similar physiological responses are noted in infants, providing a useful test method; however, it requires the infants to be awake and alert, and age differences may impact arousal levels.
Sensitivity to Depth Cues
Kinetic Cues:
Present from 1-3 months; consist of stimuli generated by the movement of objects or persons.
Binocular Depth Cues:
Develop from 4-6 months; arising from the disparity of images between the eyes, which is greater for objects close than far away.
Pictorial Distance Cues:
Emerge at 5-7 months, including linear perspective and texture gradient; tested through reaching studies.
Conclusion:
Infants gain significant knowledge about visual cues related to depth and distance within the first six months of life.
Auditory Perception
Hearing in Infants:
Equally as significant as vision, assessing auditory perception can be challenging. Various methodologies can be used, such as habituation paradigms to measure responses in head/eyes to sounds.
High-Amplitude Sucking (HAS) Methodology
Sucking behavior diminishes as the infant habituates to a sound, followed by increased sucking when a different sound is presented, indicating discrimination capabilities.
Eimas et al., 1971:
Investigated early auditory abilities in newborns using a method where sound plays in response to sucking.
Early Auditory Perception Insights
Fetuses can respond to sound as early as 24 weeks in utero, with external sounds learning from the womb.
At Birth:
Infants respond to sounds through reflexes like startle, and they show preferences for complex sounds over pure tones.
Age Insights:
By three days, infants can distinguish between two- and three-syllable words, happy versus negative speech, and ascending versus descending tones, which are crucial for social interaction and speech.
Music and Sound Perception
Infants begin to perceive musical structures early:
Newborns can detect rhythm, sensitivity to tempo and melody enhances by 6 months, and at 9 months, they show sensitivity to melody complexity with preferences for consonant music.
Olfactory and Gustatory Perception
Well-developed by the time of birth and initially influenced by experiences formed in utero.
Newborns exhibit age-dependent variations in taste preferences, stabilizing around 6 months.
Tactile Sensitivity
Touch Sensitivity:
Infants respond to touch as early as 8 weeks gestation, essential for environmental exploration and emotional development.
Haptic Perception:
Utilizes touch for object exploration, with oral manipulation being the most informative; manual manipulation capabilities develop significantly by 3 years.
Pain Perception in Infants
Infants express responses to pain through distress signals; reactions are influenced by environmental context, including caregivers' behavior.
Intermodal Perception
Definition:
Ability to combine sensory inputs into unified perceptions, crucial for understanding object events (e.g., lip movements paired with voice).
Classic Study (Meltzoff & Borton, 1979):
One-month-olds showed longer looking times at pictures that matched their tactile experience (smooth vs. bumpy dummy), indicating intermodal perception.
Support for innate intermodal skills that enhance with experience documented by Kay & Bower (1994).