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latent content In psychoanalytic interpretation, the actual wishes and concerns that a dream or behavior is intended to express; usually contrasted with manifest content.
latent learning Learning that occurs without being manifested by performance.
lateral geniculate nucleus An important neural waystation on the path from the eye to the brain; ganglion neurons on the retina send their signals to the lateral geniculate nucleus; from there, other neurons carry the signal to the visual cortex in the occipital lobe.
lateral inhibition The tendency of adjacent neural elements of the visual system to inhibit each other; it underlies brightness contrast and the accentuation of contours. See also brightness contrast.
lateralization An asymmetry of function of the two cerebral hemispheres. In most right-handers, the left hemisphere is specialized for language functions, while the right hemisphere is better at various visual and spatial tasks.
law of effect A theory that the tendency of a stimulus to evoke a response is strengthened if the response is followed by reward and is weakened if the response is not followed by reward. Applied to instrumental learning, this theory states that as trials proceed, incorrect bonds will weaken while the correct bond will be strengthened.
learned helplessness A condition created by exposure to inescapable aversive events. This retards or prevents learning in subsequent situations in which escape or avoidance is possible.
learned helplessness theory The theory that depression is analogous to learned helplessness effects produced in the laboratory. See also learned helplessness.
learned taste aversion A specialized form of learning in which an organism learns to avoid a taste after just one pairing of that taste with illness. For example, an animal will avoid a food that on an earlier occasion made it sick.
learning curve A curve in which some index of learning (e.g., the number of drops of saliva in Pavlov's classical conditioning experiment) is plotted against trials or sessions.
learning model As defined in the text, a subcategory of the pathology model that (1) views mental disorders as the result of some form of faulty learning, and (2) believes that these should be treated by behavior therapists according to the laws of classical and instrumental conditioning or by cognitive therapists who try to affect faulty modes of thinking. See also cognitive therapy.
learning theorists A group of theorists who argued that most learning can be understood in terms of a small number of principles that apply to all organisms and all situations.
lens The portion of the eye that bends light rays and thus can focus an image on the retina.
leptin A chemical produced by the adipose cells that seems to signal that plenty of fat is stored and that no more fat is needed. This signal may diminish eating.
lesions The damage incurred by an area of the brain.
lexical decision task A task in which the participant must decide as quickly as possible whether a stimulus (book, trup, filt) is or is not a word.
life-span development The process of change and development that can be observed across the entire span of life, from prenatal development to death.
limbic system A group of interconnected subcortical structures crucial for many emotional and motivaton activities, and many aspects of learning and memory. The limbic system includes the hypothalamus, the amygdala, and other structures.
linear perspective A cue for distance that can be portrayed on a flat surface, exploiting the fact that objects appear smaller if viewed from a distance, and that parallel lines seem to converge as they recede into depth.
line of best fit A line drawn through the points in a scatter diagram. It yields the best prediction of one variable when given the value of the other variable.
lobes Rounded substructures within a larger organ. The brain, for example, contains four major lobes — the frontal, parietal, temporal, and occipital.
localization of function The process of determining what each region of the brain contributes to which aspects of thinking and behavior.
local representations A model of cognitive organization, especially semantic memory, in which each concept is represented by a single node or, more plausibly, a group of nodes. See also distributed representations, node.
lock-and-key model The theory that neurotransmitter molecules will only affect the postsynaptic membrane if their shape fits into that of certain synaptic receptor molecules.
longitudinal fissure The front-to-back cleavage that divides the left and right hemispheres of the brain.
long-term memory Those parts of the memory system that are currently dormant and inactive, but have enormous storage capacity. See also stage theory of memory, working memory.
long-term potentiation (LTP) A form of cellular plasticity in which a postsynaptic neuron becomes more sensitive (potentiated) to the signal received from the presynaptic neuron. This potentiation is usually produced by a rapid and sustained burst of firing by the presynaptic neuron. The potentiation can then spread to other presynaptic neurons provided that they have fired in the past at the same time as the presynaptic cell that produced the potentiation in the first place. See also activity dependence.
loss aversion A strong tendency to regard losses as considerably more important than gains of comparable magnitude, and, with this, a tendency to take steps to avoid possible loss.
LTP See long-term potentiation.
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