Psych 311 -
Psychophysical Development
OUTLINES
Chapter 8
Learning & Memory
Rev. 2/4/03
Return to Syllabus
I. Introduction
A. Survival depends greatly on an organism’s ability to acquire behaviors that allow it to meet challenges posed by the ever-changing environment.
B The ability to acquire behavior is present to birth or hatching.
C. Learning vs. Performance
1. Learning
a. Definition: a theoretical concept that cannot be directly measured. Instead, it is inferred from a subject’s performance.
2. Problem
a. Difficult to determine whether a given factor affects learning or performance, whether it influences the organism’s capacity to modify its behavior or its ability to perform the appropriate response.
3. It is more difficult for younger animals to perform than older animals.
III. Acquisition
A. Classical Conditioning
1. With regard to learning and memory, classical conditioning is looked at in a new way.
2. The conditioned stimulus (CS) allows the organism to anticipate and prepare for the arrival of the unconditioned stimulus (UCS) that will reflexively evoke an unconditioned response (UCR).
B. Data from Nonhumans
1. Caldwell and Werboff (1962)
a. Earliest demonstration of classical conditioning in young animals
b. Results showed that young rats elicited similar responses to adults when delivered electrical shocks.
c. Findings suggest that the rat’s capacity to display classical conditioning is present at birth at a level comparable to that of an adult.
2. Hyson and Reidy (1984)
a. Their study revealed that age is a decisive factor in determining the effectiveness of CS-UCS pairings.
b. Found that increasing the intensity of the CS does not facilitate conditioning.
3. Moye & Rudy (1985) and Vogt & Rudy (1984)
a. Presented similar findings regarding visual and gustatory system.
b. 6 day old pups can discern the presence of sucrose, the ability to associate its taste with illness produced by injections of Lithium Chloride and thus eventually avoid sucrose, a phenomenon referred to as taste aversion learning, does not emerge until day 12.
c. Learning depends on a relevant sensory system development, a process that proceeds in a caudal to rostral direction.
4. Caldwell & Werboff (1962)
a. Successful Classical Conditioning of one-day-olds with a tactile CS by using a vibrating rod in the chest.
5. Possibility that disparity involves differential Maturation Rates of sensory systems.
a. Gottlieb (1971) & Scherrer (1968)
1) Report sensory systems subserving touch and kinesthesis do mature earlier than modality systems.
6. Rudy & Cheatle (1977)
a. Reported that odor aversion learning was learned on day 8, when first testing started on 2 day old rats.
b. Odor aversion learning is generally the case that the ability to bridge a delay interval increases with advancing age.
1) This does not mean that subjects younger than a certain age are unable to acquire any information when a delay is imposed between CS and UCS.
7. Miller, Molina, & Spear (1990)
a. Important observation that 4-day-old rats do not avoid an odor when a 15 minute delay is imposed between its cessation and the imposition of an illness producing UCS.
1) They do, at a later time, avoid another stimulus that has been paired with that odor.
C. Data from Humans
1. Bogen
a. Studied 3 ½ year old child whose esophagus was constricted as a result of ingesting lye.
1) Used a fistula to collect gastric secretions.
2) Had to directly place food and drink in stomach.
3) Chewing and swallowing meat produced gastric secretions.
4) Gastric secretion also found when child observed or talked about meat.
5) A trumpet paired with meat or food conversation later made the child have gastric secretion when only the trumpet was sounded.
2. Early investigations heralded Classical Conditioning in human infants.
a. Influenced by Pavlov’s work.
b. As a negative, they dealt almost exclusively with UCS’s, thereby limiting CR’s and URC’s.
3. Aversive UCS
a. Watson and Raynor (1920)
1) Famous study of UCS
a) 11 month year old boy, Albert
b) Confronted with a white rat and strikes a steel bar with a hammer
c) Noise frightened Albert
d) Procedure repeated, after one week Albert did not reach for white rat
2) Watson and Raynor believed they had conditioned child’s fear of rat (CS) with loud noise (aversive UCS)
3) Church argued that this was instrumental conditioning because child was exposed to aversive stimulus after he touched the rat
a) Therefore, instrumental punishment made him fear the rat
b) The conditioning in this experiment was a combination of classic and instrumental procedures
b. Little, Lipsitt and Rovee-Collier (1984)
1) Paired a tone with a puff of air to an infant’s eye
2) Infants as young as 10 days showed “eye blink” conditioning
4. Temporal Conditioning
a. Marquis (1941)
1) Used infants on a 3-hour feeding schedule for 9 days
2) Changed them to a 4-hour feeding schedule
3) After change infants displayed increased fussiness and crying 30 minutes before 4 hour feeding
4) The 3-hour time passage served as CS, expectancy of milk the CR
b. Krachkovskia (1959)
1) Studied elevation of leukocytes
2) Leukocytes are related to maturation of infant’s digestive processes and occur within the first week of life
3) Subject to temporal conditioning
a) Elevated leukocyte count after feeding is due to physical factors
b) Elevated “L” count before feeding is a CR due to time passed between meals
c) Tested infants that were changed from 3-hour to 4-hour feeding schedule
d) 1st day white blood cells appeared before what would be the 3 –hour feeding
e) 2nd day “L” count increased before new 4-hour feeding
5. Conclusions
a. Infants can be classically conditioned using positive and aversive UCS
b. Temporal conditioned response depends on the nature of the CR
c. Young of most mammalian and avian species have the ability to learn the timing of specific events and to anticipate them has immediate and direct survival implications
6. Effect of age
a. Non-human subjects capacity to acquire a CR soon after birth depends on the level on maturation of the sensory system corresponding to the modality of the CS.
b. Blass, Ganchrow, and Steiner (1984)
1) Demonstrated that infants 2 to 48 hours old can acquire a conditioned response.
2) The CS consisted of stroking the middle of the infant’s forehead with the index finger once per second for 10 seconds, and the UCS was delivery of a sucrose solution directly into the mouth. The UCS elicited UCR’s termed “head-orient” and “pucker-suck”.
3) Head-orienting and pucker-suck reactions of the experimental group generally anticipated the UCS and thus were considered CR’s.
c. Sullivan et al. (1991)
1) Performed classical conditioning on 1-day-olds; finding after repeated pairings the CS came to elicit head-turning toward the source of the odor
2) Humans, like nonhumans, appear to be capable of acquiring a CR soon after birth
D. Instrumental Conditioning
1. Instrumental conditioning is the “comprehension” of a relation between a response and reinforcement.
2. Data from Nonhumans
a. Appetitive Conditioning
1) Amsel and associates demonstrated that rats as young as 17 days can be trained to transverse a straight alley.
2) Pre-weaning animals respond in an adult manner to the schedule of reinforcement
3) It was also found that responding in the face of non-reward is inversely related to age
4) Amsel, Burdette, and Letz (1976) used nipple attachment to study the instrumental learning capacity of animals much younger than those that attained the ability to ingest solid food.
5) Kenney and Blass (1977) trained rats in a Y maze; found that animals as young as 7 days learned to discriminate between the right and left arms of the maze
6) Johanson and Hall (1979) found that 1-day-old rats are capable of acquiring and instrumental response when reinforcement is of the appetitive type
b. Avoidance Conditioning
1) Riccio and Schulenburg
a) Used passive avoidance procedure
b) 10, 15, 20, 30, & 100 day old rats shocked when they stepped from one side of the apparatus to the other.
c) Trained to remain on “safe side” for 180 seconds or for 7 trials
d) Conclusions
(1) 100 day old rats met criterion with one trial
(2) 20 to 30 day old rats required two shocks
(3) 10 day olds required six punishments
(4) 15 day old rats never met the criterion
e) The ability to acquire passive avoidance response improves with age in the rat but even young rats are capable
2) Blozovski and Cudennec
a) Animals placed in chamber cooled to 23oC (discomfort)
b) They could cross to another chamber warmed to 27oC – but doing so led to shock
c) Tested for max. of 10 trials or until they stayed in cool chamber for 300 sec
d) Other animals treated similarly except shock wasn’t delivered
e) Findings
(1) Conditioning, although at a low level, begins to appear at day 11 and increases from that time on
3) Myslivecek and Hassmannova
a) Animals goaded to enter shock chamber by passing stream of air over them
b) Animals prefer to avoid shock by staying still
c) Findings
(1) Passive avoidance learning improves with age
(2) Rats only hours old did meet learning criterion
(3) But criterion was only 60 sec – less than other experiments
(4) Argued that previous experiments reporting inferior passive avoidance learning in young rats is due to strict criteria of learning
4) Campbell and Campbell
a) Acquisition of a task requiring 18-day-old rats to move from one side – in which they’d been shocked – to safe side did not differ from 100 day olds
5) Other Data
a) 25 day old rats learned to cross to safe side in response to light signaling shock at a similar rate to 60 and 70 day old rats
b) Attests to the fact that young rats learn as well as adults when confronted with avoidance problem requiring an active response
c. Why do young appear to be on par with adults in acquiring active avoidance but inferior when challenged with avoidance task necessitating the withholding of behavior?
1) The cholinergic neurotransmitter system
a) Hypothesized to facilitate transmission among neurons involved in suppression of behavior
b) B/c young possess an immature system they are deficient in response inhibition
c) Support for this
(1) This system matures gradually
(2) Significant increases in acetylcholine are found in rat brain from birth to week 3
(3) Functional analyses reveal the system matures by the third week of life
2) Wilson and Riccio
a) Administration of a drug (scopolamine) blocking the central cholinergic transmission – increased # of trials required by 18, 21, and 30 day old rats to acquire passive avoidance response
b) 15 day olds not affected – suggesting the system matures significantly by day 18
3) Later Investigations
a) Placed anticholinergic compounds into nuclei of the developing rat brain – attempting to localize sites involved in response inhibition
b) Blozovski et al. argue that both the amygdala and hippocampus play a major role
4) Future studies should determine if deficits in young are related to response inhibition or to inhibition due to aversive stimuli
a) This could be addressed by making positive reinforcement contingent on the inhibition of behavior
c. Facilitation of Instrumental Conditioning
1) Two factors: stimulation from home environment and nursing experience
2) Stimulation from home environment
a) 16 day old rats show enhanced acquisition of a passive avoidance response if trained in presence of soiled bedding
b) Similar effect for active avoidance task
c) Even a non-typical nest odor during acquisition (such as banana) can be facilitative if the animal has been previously exposed to it
d) How stimulation from home environment is facilitative is not understood
e) Smith and Spear
(1) When removed from safe nest environment, emotional arousal increases
(2) This interferes with ability to pay attention
(3) Introduction of familiar stimuli (such as odor) may facilitate learning by decreasing arousal levels
3) Nursing Experience
a) Cramer, Pfister, Haig
(1) Proposed if demands of a conditioning task are similar to those of nursing situations, the acquisition of the instrumental response should be facilitated
(2) They found similarities between the demands of suckling and those of the radial arm maze
(3) Similarities led them to predict that animals that had restricted nipple-shifting experience should exhibit poor radial arm maze learning
4) Nursing can affect instrumental learning
a) Cramer, Pfister, Haig (1988) proposed that demands of conditioning tasks are similar to nursing situation.
(1) They analyzed between suckling and behavior of rat in arm maze.
(2) The suckling rat maximized intake by withdrawing the milk from nipple and then moving to the next.
(3) The maze supplies spatial array of food and there is a limited supply.
(4) Returning immediately to either the arm or the nipple is not rewarding.
(5) The demand for suckling and the radial maze led to predict that animals that had had restricted relatively poor radial maze learning.
b) Group of 5 day old were given to foster mother having 12 nipples or to mothers having 4 nipples
(1) Day 22 pups were given training in maze
(2) Pups exposed to many nipples during suckling period learning maze more quickly.
c) Cramer et al. addressed the issue of what nipple- shifting experiments contributed to conditionability.
(1) The influence of nipple- shifting may be specific to spatial learning because exposure to differential numbers of nipple affected neither the acquisition of a food reinforced lever pressing response nor visual crimination.
(2) It seems the experience gained by moving from nipple to nipple in an attempt to maximize the availability of milk can facilitate the learning of a task that also requires movement from place to place.
3. Data from Humans
a. Free operant procedure
1) When infant is permitted to control its response rate and thus moderate the amount of reinforcement contained within a fixed time.
2) Results revealed that stimuli of many types can serve as reinforcement for a variety of responses such as head turning panel pressing, and vocalizing.
3) Rewards have included sugar water, milk, music, nonnutritive sucking, and sight of adult.
4) Infants can be instrumentally conditioned beginning soon after birth.
4. Conjugated Reinforcement Procedure
a. Conjugated is the relation between response and reward.
1) It is believed that the conjugated schedule more accurately mirrors the normal pattern of interaction between the infant and its environment.
b. Lipsih, Pederson, DeLucia (1966)
1) 12 month olds placed in front of darkened box.
2) They were permitted to observe a rotating colorful clown by pressing a panel.
3) Increased response rate up to 2 or 3 presses/sec. Produce gradual increase in frequency and intensity of illumination.
c. Kalnins and Brune (1973)
1) Made the clarity of a silent colored motion picture contingent on the sucking rate of 5 week old infants
2) 12 infant exposed to blurred image could gradually be brought into view by sucking.
3) 12 infants exposed to a clear picture that can be made blurry by sucking.
4) Infants given blurred image displayed rapid increase in sucking rate.
5) Subjects given clear images did not increase rate of sucking.
d. Siqueland (1969)
1) Gave 1 month old infants access to colorful triangles.
2) When color of triangle changed, response rate increased.
e. Conjugated reinforcement also has been used in conjunction with kicking-produced changes in visual stimulation.
f. “Mobile” conjugated reinforcement has been confirmed many times with infants
1) Davis and Rovee- Collier reported that 8 weeks is about the earliest which infants can be conditioned.
IV. Retention
A. An organism must retain the associations learned between aspects of its environment and behavior
B Data from Non-human subjects
1. Misanin, Nagy, Keiser, and Bowen’s seminal report on the ontogeny of memory
a. Rats at 5, 7, 9 and 11 days old were placed in a straight alley in which electrical shock was delivered through the metal grind
b. Dependent measure was how many times rat turned 180 degrees away from goal.
c. Escape from shock required that the rat touch the end wall of the goal compartment
d. Rats of all ages showed improvement throughout days trials
e. Only rats 9 and 11 days old showed further improvement on days 2 and 3
f. Rats 5 an 7 days old behaved as if they had never been in the maze before
g. Concluded that the capacity to retain information across a 24 hour period emerges on about day 9 of life
1) Also reported that younger animals can retain information but they have a much shorter retention span than other animals
2. Nagy, Newman, Olsen and Hinderliter (1972)
a. Reported that 9 day olds can retain information for at least 96 hours, whereas it is much shorter for younger animals – less than 6 hours for 5 and 7 day olds
3. Nagy and Mueller (1973)
a. Gave 7 and 9 year old mice 0, 10, 25 or 40 trials in the straight alley escape task and then tested 24 hours later
1) None of the 7 day old rats exhibited retention
2) Retention was displayed by the 9 day old rats even in those given only 10 acquisition trials
b. Suggests that the superior performance exhibited by the 9 day olds is due to the emergence of the capacity to remember information over a 24 hour time span
4. Campbell and Alberts (1979) retention of taste aversion
a. Used 10, 12, 15 and 20 day old rats and tested them after intervals of 5, 10 and 15 days
b. All displayed some level of retention of the learned taste aversion
1) Less retention displayed in the 10 and 12 day old pups vs. the 15 and 20 day olds
5. Stehouwer and Campbell (1980)
a. Assessed retention following the acquisition of a passive avoidance task in which rats received a shock when they made contact with the cage walls
b. Retention increased from 6 hours in 10 day olds to 5 days in 15 day olds
c. Difference of time of retention between studies leads to the notion that a major determinant of memory span seems to be task specific
6. Bachevalier and Blozovski (1980) – supports notion of memory being task specific
a. Classically conditioned a leg flexion response using a vibrotactile CS and shock UCS in 0, 2, 3, and 4 day old rats
b. All rats, even those less then a day old retained the CS-CR association for 24 hours
7. Conclusion of 3 main factors affecting memory retention
a. Depends on the attainment of a minimal level of neurological maturation
b. Characteristics of the task determine length of time information is retained
c. Task complexity is a relevant dimension
C Infantile Amnesia
1. Dudycha and Dudycha (1941)
a. Describe five studies with human subjects in which the average ages of the earliest reported memories are 3, 3, 3.5, 3.7, and 3.8 years of age
2. Mare
a. Reviewed 270 autobiographies
b. Only 3 authors reported memories prior to the age of 2, and only 13 authors discussed events taken place prior to age 3
c. Exaggerated loss of memories of events occurred early in life is referred to as infantile amnesia
D. Alleviation of infantile Amnesia
1. Campbell and Jaynes (1966)
a. reinstatement concept - denote a small amount of an experience over the developmental period, which is enough to maintain an early learned response, but is not enough to produce any effect in animals, which have not had the early experience
b. 25 day old rats acquired an association between a stimulus and electrical shock
1) placed rats in a compartment which was part black and the other white
2) shock was not delivered when animals in the white compartment
3) two groups of animals placed in black compartment-shock was administered in 2-second bursts about every 20 seconds for 5 minutes
4) control group was treated identically except no shock was given
5) shock and reinstatement was give 7, 14, and 21 days after the original training
6) animals spent time in white compartment either before or after reinstatements
7) at 53 days of age animals tested by placing them in black compartment with the door removed enabling them to run into the white compartment
8) those that had early experience with shock and reinstatements remembered the black with punishment
a) reinstatement stimulus by itself is incapable of establishing the learned fear response
c. infantile amnesia can be alleviated by exposing animals to a truncated form of the original conditioning experience by “reminding” them about the event
2. also can be alleviated by ensuring that stimuli present within the context of the original learning situation are also present during later testing (known as contextual matching)
3. Solheim, Hensler, and Spear (1980)
a. young animals trained to perform an active avoidance response in the presence of an odor and tested in the presence of a different odor exhibit a retention deficit relative to animals that were trained and tested in the presence of the same odor
b. contextual matching is effective
4. Richardson, Riccio and Jonke (1983)
a. 21 day old rats injected with pentobarbital
1) exhibited better retention when tested after pentobarbital treatment than animals that received the drug during acquisition and saline during testing
5. as described by Skinner context associated with reinforced responding acts as a “setting event” (discriminative stimulus) that signals the availability of reinforcement
a. responding occurs only when the discriminative stimulus is present
E. Data from Humans
1. Visual Attention Studies
a. infants from 2 to 12 month are believed to retain information for only a matter of minutes
b. infants are briefly exposed to a stimulus and after a delay are presented with the same stimulus and a novel stimulus
1) infants will have habituated to the familiar stimulus during initial presentation therefore preferring to gaze at the novel stimulus
c. by delaying the presentation of the original plus the novel stimulus one can determine the infants retention capacity
d. Delayed response task
1) varies the time between the presentation of a visual stimulus and reinforcement
2) Diamond and Doar (1989)-attracted the attention of an infant by holding up a toy
a) toy placed in one of two hiding wells
b) after a delay of 0 to 12 seconds the infant was allowed to reach for it and if successful they could play with the toy
c) it is shown that infants have a short retention capacity – only 50% of 12 month olds were able to reach the learning criterion with a delay of 8 seconds, none tolerated the delay of 12 seconds
3) infants lack the capacity to retain information for periods longer than a few minutes
2. Conditioning studies
a. Greco et al. (1986) and Sullivan, Rove-Collier and Tynes (1976)
1) using the kicking-produced “mobile” conjugate reinforcement technique
2) 2 and 3 month old infants to 2- 15 minute acquisition sessions on consecutive days followed later by a 15 minute long term retention session
3) 3 month olds exhibited significant retention after as long as an 8 day delay between acquisition and retention
b. Results
1) showed that infants are able to retain information for much longer time then they previously been reported form visual retention research
2) within the context of a conditioning analysis human infants possess the capacity to retain information about an event for periods of time well beyond the few seconds of minutes reported by investigators who assess memory with visual attention tasks.
3. Instrumental conditioning techniques
a. Allows the infant to control its environment and “that the greater the degree of control infants are allowed to exert over their sources of environmental stimuli on the more robust are the demonstrations of their learning and memory prowess
III. Conclusions
A. At a very early age humans and nonhumans alike possess the ability to form associations between stimuli and between responses and their outcomes
B. most associations formed during early life are eventually forgotten a phenomenon called infantile amnesia
1. A functional analysis of infantile amnesia although a difficult undertaking may add to our understanding of the ontogeny of learning and memory