PSY 211 1st Edition Lecture 7Outline of Current Lecture I. Sensation and PerceptionII. VisionIII. PsychophysicsCurrent LectureSensation and PerceptionSensation is the detection and translation of stimulus energy into neural activity. Perception is the organization and interpretation of sensation into a meaningful object or event. There isn’t a fine line between the two. An interesting question is the degree to which attention gets involved in the processes of sensation and perceptionStages of Sensation and Perception1. Stimuli (physical energy) activates sense receptors.2. Physical energy is translated into neural activity (transduction).3. Early neural processes organize the sensory input, separates from the ground, and extract critical feature via “feature detectors” (neurons that respond to basic or simple features of the world).4. Stimulus features are reconstructedinto holistic representations and compared to store representations (schemas and instances) in memory.5. Matching process results in perception—the recognition and interpretation of the stimulus. Five Senses1. Vision- rods and cones, electromagnetic energy2. Hearing-cochlea, mechanical energy (from sounds of pressure waves)3. Smell-Olfactory receptor cells, chemical compounds4. Taste- taste buds, chemical compounds5. Touch- free nerve endings and Meissner Corpuscle, mechanical energy (pressure).In addition to these fine “classic” senses, we also have processes devoted to the sensations of temperature, the position and movement of our bodies, pain and the passage of time.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.VisionThe Eye:Transduction of light into a coherent pattern of neuro-chemical and electrical activity. There are no photoreceptors at the optic disc, where the optic nerve exits the eyeball. This is what createsa “blindspot” in your vision.Photoreceptors- Rods- see in black and white, dim light, poor acuity, and periphery- Cones- see in color, bright light, detail, foveaBipolar Cells has information for integration and ganglion cells have dot detectors, axons form optic nerve, and the blindspot.Note that the temporal (outside) portion of the each retina projects ipsilaterally (same hemisphere), while the nasal (inside) portion projects contralaterally (to other hemisphere). Thus a stimulus in the left visual field (LVF) is projected to the right hemisphere (RH), and vice versa. Cortical Pathways: visual area and pattern of connectivity in the macaque monkey, single cell recording. Receptive Fields: area of space in which a stimulus will alter the activity of a neuron. As you go higher into the visual system the size of the receptive fields increase. Feature Detectors: cells in the primary visual cortex, simple and complex orientation-detection cells. PsychophysicsPsychophysicsis the study of relationships between conscious experience and the physical world. Absolute Thresholds- The lowest intensity allowing 50% detectionDifference Thresholds- The smallest differences that people can detect 50% of the time. ( called the Just Noticeable Difference or JND)- Weber’s Law of JNDs for any modality, JND’s will be a constant proportion of a standard intensity.o The more intense a stimulus, the larger the change will need to be for a difference to be noticed.o Weber’s Fraction: k= ∆I / Io It does fail when it comes to pain. Psychophysical research on absolute & difference thresholds clearly shows that a person's thresholds change as a function of multiple factors (including arousal/alertness, expectation, incentives, etc.).Signal Detection Theory was invented to separate a person’s ability to truly detect target stimuli, and their tendency to say “yes, I’ve detected it.” People differ in their ability to detect a stimulus and how often they say they’ve detected a stimulus. - Sensitivity - Person's true ability to discriminate targets (signal) from non-targets (noise).- Response Criterion (Bias) - Person's tendency to claim they have detected a signal ("yes").Subliminal Perception The thought and behavior can be influences by stimuli. - Blindsight – the ability to correctly identify or respond to visualstimuli, despite having noconscious awareness of them, usuallydue to damage to primary visual