Learning Approaches

Behaviourism developed largely out of dissatisfaction with the psychodynamic approach and earlier theories of consciousness. John Watson (he of Watson & Raynor fame and Little Albert) wanted a theory of behaviour that was testable. The problem was in the early decades of the twentieth century there was no way of recording brain activity let alone mental processes. Result … ignore the workings of the brain, treat it as a black box, receiving information from the environment (stimulus) and creating a reaction (response). At its simplest behaviourist psychology is simply that: stimulus-response (S-R) psychology.

Behaviourists therefore believe that we are a product of our environment. At birth we are a ‘tabula rasa’ or blank slate. Our genetic make-up is largely ignored. Our personality, intelligence, achievements and behaviour are shaped by the environment in which we are reared. Behaviourism is therefore at the extreme nurture of the nature-nurture debate. However, like the psychodynamic theory it is determinist, seeing our outcomes as under the control of our environment rather than of our unconscious minds.

Behaviourism: Classical Conditioning

Pavlov noticed that his dogs would start to salivate when they heard the footsteps of the research assistant who they knew was going to feed them. Pavlov realised that the dogs had learned to associate food with the footsteps and wondered if this association would extend to other things, most famously the ringing of a bell.

Although the terminology seems daunting, if you just remember that conditioning refers to learning it helps.

The NEUTRAL STIMULUS (NS) is something that you would typically have little to no reaction to, in Pavlov’s case it is the BELL. The UNCONDITONED STIMULUS (UCS) is something that would usually create some form of response, in Pavlov’s case the unconditioned stimulus in the FOOD. The UNCONDITIONED RESPONSE (UCR) is one that does not require learning, such as a reflex. In Pavlov’s case it is SALIVATION. You do not learn to salivate to food, it happens naturally from birth. When the NS is paired with the UCS this produces the UCR. This pairing can happen once, or many times, either can lead to a conditioned behaviour. If the association has been conditioned. The NS now becomes the CONDITIONED STIMULUS (CS) and the UCR now becomes the CONDITIONED RESPONSE (CR). In Pavlov’s case, every time the dog hears the bell (CS) it leads to salivation (CR).

Watson carried out a study which wanted to investigate if a fear could be learned through the process of classical conditioning. Watson decided to use a young baby called Albert as the participant.

In the case of Little Albert, the NS was the rat and this was paired with the UCS of a loud bang and the UCR is being frightened. Once the NS and the UCS was paired again and again, this lead to the rat becoming the CS and being frightened as the CR. Albert was then terrified whenever he was in the presence of a rat. He even became scared of things that were fluffy and white and this is known as GENERALISATION.

Watch the video below to see footage of both the little Albert study and Pavlov’s study:

The cruelty of Pavlov

Despite the jokes, ‘that rings a bell’ etc. and Pavlov’s fluffy image as a man that made his dogs salivate to the sound of a bell, his research was quite unpleasant. The dogs were clearly mistreated and fitted with surgically fitted catheters to collect every drop of saliva.

Practice identifying the NS, UCS, UCR and CS and CR.

This is a typical exam question that you will be asked, and it is essential that you use behaviourist terminology. The answers are at the bottom of this blog page.

Suzy goes outside to play in her tree house. A swarm of bees has nested near her house, and she gets stung several times when she climbs up to the tree house. This happens 3 times in a week. Suzy then becomes afraid to go near the tree and cries violently when her dad tries to get her to climb up to the tree house.
Jerry’s wife, Mary, gets a new nightgown and wears it whenever she is in the mood for sexual relations. After a month, the sight of the nightgown alone is enough to excite Jerry
A student went on holiday and was eating some peanuts on the plane. Whilst he was eating the peanuts, the plane malfunctioned and crashed. The student survived the plane crash, but whenever the student sees peanuts, he gets anxious.
While caring for a friend’s dog, you notice that it displays a fear-like posture as you roll up a newspaper. You try this several times more and become convinced that this dog is generally afraid of rolled-up newspapers. You must infer on your own what happened to make this dog afraid of rolled-up newspapers.
Joan, an animal trainer, has been phobic about monkeys since an earlier attack. However, because of the money, she has agreed to work with monkeys for a movie studio. At first, just going anywhere near the cages makes Joan tense, sweaty and apprehensive. Lately, though, things have changed. Working with such cuddly, affectionate, human-like creatures is causing Joan to wonder why she ever felt such extreme distress. Identify what original NS, UCS, UCR, CS, and CR were to make Joan afraid of the monkeys. In addition, identify the processes of counter-conditioning (what made her no longer afraid of monkeys).
Bill visited a restaurant in the beginning of November and ordered the chicken. Afterwards, he became extremely sick and nauseated. Ever since then, he has been unable to even think about chicken without becoming nauseated. He went to his mums for dinner who had cooked a turkey. He was quite surprised to find that he felt slightly nauseated to the smell and sight of the turkey. However, he didn’t feel nauseated to the smell or sight of the roasted duck his cousin brought to the dinner. Identifying all of the processes, you should also be able to identify at least 2 principles.

Behaviorism: Operant Conditioning

Burrhus Frederick Skinner is known for developing a theory called operant conditioning. Skinner carried out research on rats and pigeons in his Skinner boxes to support his theory.

Students are often confused about the difference between these two forms of conditioning.

Classical conditioning is simply the associative learning = Pavlov

Operant conditioning involves learning through consequences = Skinner

To discover the precise effect of reinforcement and punishments on behaviour Skinner would observe animals in laboratory conditions where environments could be tightly controlled.

Operant conditioning: Positive Reinforcement

Skinner showed how positive reinforcement worked by placing a hungry rat in his Skinner box. The box contained a lever on the side, and as the rat moved about the box, it would accidentally knock the lever. Immediately it did so a food pellet would drop into a container next to the lever.

The rats quickly learned to go straight to the lever after a few times of being put in the box. The consequence of receiving food if they pressed the lever ensured that they would repeat the action again and again.

Positive reinforcement is where a reward encourages a behaviour.

Typically positive reinforcement is used to encourage desirable behaviour. For example, giving my dog a treat every time he waits at the curb before he crosses the road. However, sometimes positive reinforcement can encourage undesirable behaviours. For example, if a toddler is screaming and having a tantrum in a supermarket and the parent gives the child a sweet to be quiet. The child will be encouraged to have a tantrum in the hope that they will be given a sweet again!

In this video we see an example of positive reinforcement with Penny and punishment with Lenard.

Operant Conditioning: Negative Reinforcement

Negative reinforcement doesn’t always mean that something bad happens. A negative reinforcer is something that takes away an unpleasant consequence in order to encourage a behaviour. For example, taking paracetamol that takes away a headache. The removal of the unpleasant headache makes the behaviour that preceded it, taking paracetamol, more likely in future.

Skinner showed how negative reinforcement worked by placing a rat in his Skinner box and then subjecting it to an unpleasant electric current which caused it some discomfort. As the rat moved about the box it would accidentally knock the lever. Immediately it did so the electric current would be switched off. The rats quickly learned to go straight to the lever after a few times of being put in the box. The consequence of escaping the electric current ensured that they would repeat the action again and again.

Extinction

This is when a previous learned behaviour is unlearned. Skinner found that after the rats had learned to press the leaver to receive food, he could get the rats to unlearn this behaviour. Skinner stopped feeding the rat when it pressed the lever. After the rat had experienced no food after pressing the lever several times, the rat eventually stopped pressing the lever. The rat eventually learned that the behaviour had no reward, and therefore stopped doing it.

The difference between Reinforcement and Punishment

Reinforcement: anything that increases the chances of a behaviour being repeated

Punishment: anything that discourages and decreases the likelihood of a behaviour being repeated

Types of reinforcers:

Primary reinforcers are ones that satisfy a biological need, for example food, drink, sex.

Secondary reinforcers are reinforcers that we have come to associate with primary reinforcers.

Money: will buy us primary reinforcers
Promotion: will get us more money so we can buy primary reinforcers
Exam success: will help us get promotion so we have more money…

Other secondary reinforcers would include smiles, compliments, gifts etc. Secondary reinforcers are every bit as powerful as primary reinforcers.

Evaluation of the behaviourist approach

Point: A key limitation of the behaviourist approach is the issue of generalisability from Skinner’s research using animals to human behaviour. Evidence: Skinner’s operant conditioning studies were conducted in highly controlled laboratory environments using rats in a Skinner Box, where extraneous variables were minimised and behaviour was shaped through reinforcement. Explain: While this allowed for precise measurement and the establishment of cause-and-effect relationships, critics argue that such artificial conditions lack ecological validity and do not reflect the complexity of real-life human behaviour. Human actions are influenced by cognitive processes, emotions, and social contexts, which are largely ignored in behaviourist explanations. This suggests that behaviour cannot be fully understood through simple stimulus-response associations alone. Consequence: Consequently, the findings from animal studies may only provide a partial explanation of human behaviour, limiting their external validity. Challenge: However, it could be argued that the use of animals allows researchers to control variables that would be ethically and practically impossible with humans, meaning that such studies are valuable for establishing basic learning principles. Therefore, although Skinner’s research offers important insights into behavioural processes, its ability to generalise to the complexity of human behaviour is restricted.
Point: There is research to support behaviourism. Evidence: Skinner carried out am experiment with caged rats, where he rewarded the rats with food, every time they pushed a lever. Eventually this behaviour became more frequent and deliberate. Explain: This demonstrates positive reinforcement as it shows that the reward of food, encouraged the rat to repeat the new behaviour of pushing a lever. Consequence: Consequently, due to having supporting research, the behaviourist approach can be seen as more credible. This allows researchers to more confidently apply behaviourism to society to make positive change. For example, teachers using positive reinforcement in schools to encourage good study habits. Challenge: However, whilst the study supports operant conditioning, the use of animals to support behaviourism may reduce the applicability to human behaviour. Although there is some evidence that behaviourism applies to humans, it is clear that humans are far more complex, so behaviourism may not provide a full explanation of human behaviour.
Point: A key limitation of the behaviourist approach is that it is overly deterministic. Evidence: Behaviourism suggests that behaviour is entirely shaped by environmental stimuli and reinforcement histories, leaving little room for free will. Explain: This environmental determinism implies that individuals have no control over their actions, which is a reductionist and arguably unrealistic view of human behaviour. In reality, people actively process information and make conscious decisions, as highlighted by the cognitive approach. Consequence: Therefore, behaviourism may provide an incomplete explanation of behaviour by ignoring the role of internal mental processes. Challenge: Additionally, behaviourism has difficulty explaining behaviours that involve no obvious reinforcement history. For example, language acquisition cannot be fully explained by operant conditioning alone. This suggests that behaviourism fails to account for biological predispositions, further weakening its completeness as a theory of behaviour.
Point: One strength of the behaviourist approach is that the principles of classical conditioning have clear real-world applications, particularly in the treatment of phobias. Evidence: Behavioural therapies such as systematic desensitisation and flooding are based on the idea of forming new associations with a feared stimulus, replacing the conditioned fear response with a more relaxed or neutral response. Explain: These therapies have been shown to be highly effective in reducing phobic anxiety, demonstrating the practical value of behaviourist principles. Consequence: This increases the external validity of the approach, as findings from controlled research have been successfully applied to real-life problems, improving individuals’ wellbeing and ability to function in everyday life. Furthermore, the success of these treatments provides empirical support for the role of conditioning in the development and treatment of abnormal behaviour. Challenge: However, it could be argued that such therapies may not address the underlying cognitive causes of phobias, meaning that behaviourism may only treat the symptoms rather than the root cause. Therefore, while classical conditioning offers significant practical benefits, its explanatory power may be limited when used in isolation.
A further limitation of the behaviourist approach is that it is highly reductionist, as it simplifies complex human behaviour to basic stimulus–response associations. For example, Pavlov’s theory of classical conditioning suggests that behaviour is learned through forming associations between stimuli, and his research relied on isolating variables in tightly controlled experiments to demonstrate this process. While this allows for precise scientific study, it ignores the influence of cognitive processes and social context on behaviour. Human actions are not purely automatic responses, but are shaped by thoughts, expectations, and social interactions, which are emphasised by approaches such as the cognitive and social learning theories. This means that behaviourism may provide an oversimplified explanation of behaviour, limiting its explanatory power. However, it could be argued that a reductionist approach is beneficial in psychology because it allows researchers to isolate variables and identify general laws of behaviour in a scientific and systematic way. Therefore, although behaviourism has contributed to the development of psychology as a science, its reductionist nature means it cannot fully account for the complexity of human behaviour.

Social Learning Theory (SLT)

SLT burst onto the scene in the early 1960s, half a century after Watson and co had established behaviourism as a major force in psychology. The founding father was Albert Bandura who believed that we learn by imitating others and that learning takes place in a social context. Bandura believed that behaviour was a result of observing a role model and imitating their behaviour. He aimed to prove his theory using his Bobo doll experiment.

Some key ways that SLT builds and differs from Behaviourism:

Behaviour is learned through observation and imitation, not just direct reinforcement – Bandura really wanted to support the idea that learning can occur without direct reinforcement!
It acts as a bridge between behaviourism and the cognitive approach
Learning involves mental processes, not just stimulus–response

The next section will cover the key aspects of SLT that you will need to know for your exams, and these include:

Vicarious Reinforcement
Mediational Processes
Identification
Bandura’s Bobo Doll study

Vicarious Reinforcement:

There is also a type of reinforcement for Social Learning Theory called Vicarious reinforcement. Be really careful with this in your exams. Students have often confused this with positive reinforcement and negative reinforcement. If you notice the exam question talking about observing another person being rewarded, this is vicarious reinforcement.

Vicarious reinforcement occurs when (a) an individual observes another person behave in a certain way and experience a consequence perceived as desirable/undesirable by the observer, and (b) as a result, the observer behaves as the model did. For example, a student who hears the teacher praise a classmate for effort on a 16 mark essay, she particularly loves the use of the PEECC structure. The student who overhears may then put a great deal of effort into their next 16 mark essay in the hope that they will also receive praise from their teacher.

Mediational Processes:

A good acronym to explain the mediational processes of SLT is ARRM:

The first process is attention, which refers to how much the individual notices the behaviour. For example, people are more likely to pay attention to models who are attractive, high status, or similar to themselves.
The second process is retention, which involves remembering the behaviour. This may involve storing a mental image or verbal description so that the behaviour can be recalled later.
The third process is reproduction, which is the ability to physically and mentally carry out the behaviour. For example, a person must have the necessary skills and capabilities to imitate what they observed.
Finally, motivation determines whether the behaviour is actually imitated. This is influenced by expected rewards, including vicarious reinforcement, where individuals are more likely to imitate a behaviour if they see the model being rewarded.

A classic question that AQA LOVES to ask about mediational processes, is an application question. For example: Use your knowledge of mediational processes to explain why some teenagers imitate aggressive behaviour they see on social media while others do not. (6 marks)

Model answer:

Firstly, attention is important. Teenagers are more likely to notice and focus on aggressive behaviour if the person displaying it is popular or high status, such as an influencer. Secondly, retention determines whether they remember the behaviour. If the behaviour is memorable, for example because it is dramatic or repeated frequently, it is more likely to be stored and recalled later. Thirdly, reproduction affects whether the teenager is able to imitate the behaviour. Some may lack the confidence or physical ability to act aggressively, so they do not copy it. Finally, motivation is crucial. Teenagers are more likely to imitate aggression if they see the influencer being rewarded, such as gaining likes or attention. This is known as vicarious reinforcement. However, if they see negative consequences, they will be less likely to imitate. Therefore, not all teenagers copy aggressive behaviour because these cognitive processes influence whether imitation occurs.

Identification:

Identification is when an individual adopts the attitudes or behaviours of a model because they want to be like them. It is more likely when the model is: Likeable or admirable, Similar (e.g. same age, gender), Attractive or High status (e.g. celebrities, influencers).

It is really important to understand the difference:

Imitation = copying behaviour
Identification = the reason why you choose to imitate

See if you can link all the 3 aspects of SLT e.g. Mediational Processes, Vicarious Reinforcement and Identification to the Bandura study outlined below.

Bandura – Lab Experiment:

Albert Bandura and the Bobo doll (1961)

Research method: This was a laboratory experiment which used an matched-pairs design.
The independent variables (IVs) were:
(i) Whether the child witnessed an aggressive or a non-aggressive adult model in the first phase of the experiment (a control group was not exposed to an adult model).
(ii) The sex of the model (male or female).
(iii) The sex of the child (boy or girl). The dependent variable (DV) was the amount of imitative behaviour and aggression shown by the child in phase three.

Sample: 72 children (36 boys, 36 girls), aged 37-69 months (mean 52 months), from Stanford University Nursery School. Participants were matched through a procedure which pre-rated them for aggressiveness. They were rated on four, five-point rating scales by the experimenter and a nursery school teacher, both of whom were well acquainted with the children.

Procedure:

Phase 1:
Children in the experimental conditions were individually taken into a room and sat at a table to play with potato prints and picture stickers for 10 minutes whilst:
– The aggressive model began by assembling a tinker toy set but after about a minute turned to a Bobo doll and spent the remainder of the period physically and verbally aggressing it using a standardised procedure.

– The non-aggressive model assembled the tinker toys in a quiet manner, totally ignoring the Bobo doll.
– The control group did not participate in Phase 1.

Phase 2:
All the children were then taken individually to an another room and subjected to mild aggression. Initially they were allowed to play with some very attractive toys including a fire engine, doll set and spinning top, but after about two minutes the experimenter took the toys away saying they were reserved for other children.

Phase 3:
Children were then taken individually into a third room which contained both aggressive and non-aggressive toys e.g. 3ft high Bobo doll, a mallet, dart guns and non-aggressive toys e.g. tea set, cars, dolls. They were observed through a one-way mirror for 20 minutes whilst observers recorded behaviour with inter-scorer reliability of .90 i.e. A very high concordance rate – therefore high reliability.

Results:

Children in the aggressive condition showed significantly more imitation of physical and verbal aggressive behaviour and verbal responses than children in the non-aggressive or control conditions.
Children in the non-aggressive condition showed very little aggression, although results were not always significantly less than the control group.
Boys imitated male models more than girls for physical and verbal aggression, non-imitative aggression and gun play.
Girls imitated female models more than boys for verbal imitative aggression and non-imitative aggression.
Overall boys produced more imitative physical aggression than girls.

Evaluation of Bandura:

Strengths:

Used a lab experiment and therefore very standardised reducing the chance of extraneous variables. All participants went into the same rooms, used the same toys and were in each room for the same amount of time.
Quantitative data was collected and therefore is was easy to compare the level of imitated aggression across the conditions i.e. same sex model (control, aggressive, non-aggressive) opposite sex model (control, aggressive, non-aggressive) etc.
The experiment was set out as a play room, very similar to their own nursery, therefore increased ecological validity.
From this study there is a great understanding of how easily aggressive behaviours are imitated. This could lead to practical applications such as putting violent TV programmes to later times at night or changing age certificates on certain films etc.

Weaknesses:

Due to the use of a lab the study lacked realism, hitting a Bobo doll is very different from hitting a person and therefore the researchers should be cautious when applying results to real life.
Only collecting quantitative data meant that the researchers were not able to understand what the children were thinking or feeling during the study.
Use of children can raise ethical issues as they cannot give consent and they find it more difficult to withdraw. Consent was gained from the school as they were doing activities usual of nursery day to day life. However, children were deliberately annoyed by researchers as part of the second stage of the experiment, this could raise potential issues of distress.
Playing with a strange adult in an unfamiliar room is not a typical everyday task, ecological validity can be questioned.
The study had a large sample size, however, when they were broken down into the conditions, there are only 6 participants, any confounding variables could have quite a large effect on the validity of the results.

Evaluation of Social Learning Theory:

Within these PEECC’s notice that SLT terminology that is highlighted in bold. This is something I tend to see students forget to do.

Point: A strength of social learning theory is that it is supported by empirical research. Evidence: For example, Bandura exposed nursery-aged children to aggressive, non-aggressive, or no models, carefully controlling for variables such as the child’s initial level of aggression through pre-testing and matching participants. The findings showed that children were significantly more likely to imitate the behaviour of a same-sex model, highlighting the importance of identification in learning. Explain: This supports SLT because it demonstrates that behaviour is not simply learned through direct reinforcement, but through the observation of others and the influence of mediational processes such as identification and vicarious reinforcement. Consequence: As a result, this increases the internal validity of SLT, suggesting it provides a credible explanation of how behaviours, including aggression, are acquired. This has important real-world applications, for instance in using positive role models in education and media to encourage prosocial behaviour. Challenge: However, Bandura’s study was conducted in highly controlled laboratory conditions using an artificial task (interacting with a Bobo doll), which may have led to demand characteristics, as children may have inferred that aggressive behaviour was expected. Therefore, it is less certain whether these findings can be applied to more complex, real-world social environments, thereby limiting the extent to which SLT can fully explain behaviour outside the laboratory.
Point: A limitation of social learning theory is that it may offer an incomplete explanation of behaviour, as it neglects important biological influences. Evidence: For example, the biological approach would argue that the greater levels of aggression shown by boys in Bandura’s study could be explained by higher levels of testosterone, which is associated with increased aggressive behaviour. Explain: This suggests that behaviour may not be solely the result of observing and imitating role models, but instead arises from an interaction between innate biological factors and environmental influences. Consequence: Therefore, SLT can be criticised for being environmentally deterministic, as it overemphasises the role of learning through observation while underestimating the role of nature. This reduces the explanatory power of SLT, as it cannot fully account for individual differences in behaviour that may have a biological basis. Challenge: However, social learning theory is not entirely environmentally deterministic, as it incorporates mediational processes such as attention and motivation, meaning individuals actively process and evaluate behaviour before imitating it. This suggests that behaviour is not simply a result of environmental exposure, but also involves cognitive decision-making. Therefore, although SLT does not directly explain biological mechanisms, it can still contribute to a more holistic explanation of behaviour when considered alongside biological factors.
Point: A strength of social learning theory is its wide range of practical applications in real-world settings. Evidence: For example, Ansager et al. (2006) found that individuals who identify with characters in anti-alcohol campaigns are more likely to model the behaviour presented. Explain: This supports SLT by demonstrating the importance of identification and modelling, suggesting that behaviour can be influenced through exposure to appropriate role models. This highlights how SLT can be used to design effective interventions, such as promoting healthier lifestyle choices or encouraging positive behaviours through media representation. Consequence: Consequently, this increases the practical value of the theory, as it can be applied to address social issues and influence behaviour in a controlled and beneficial way. Therefore, SLT is not only theoretically significant but also useful in producing meaningful improvements in society, such as reducing harmful behaviours and promoting prosocial norms. Challenge: However, the practical applications of social learning theory may be overstated, as there is mixed evidence regarding the long-term effectiveness of modelling interventions. For example, exposure to positive role models in media campaigns may be less effective if individuals do not strongly identify with those models, limiting the impact of the intervention. This suggests that SLT may oversimplify the complexity of real-world behaviour, as it assumes that exposure to appropriate models is sufficient to produce change.

Other arguments you could make:

Research to support: Bandura’s Bobo doll into imitation of aggression. Bandura also replicated research where children watched aggression on a TV, and imitation still occurred. In addition, Fox and Bailenson (2009) found that humans were more likely to imitate computer-generated ‘virtual humans’ who were similar to themselves. These studies demonstrate support for different aspects of SLT, including modelling and vicarious reinforcement, adding credibility to the key principles of this theory.
Soft Determinism: A strength of social learning theory is that it adopts a soft deterministic perspective, which recognises the role of both environmental influences and individual cognitive processes in shaping behaviour. Unlike strict behaviourist approaches, which suggest behaviour is entirely determined by external reinforcement.

Answers for the scenarios:

Suzy: NS = Tree house, UCS = Getting stung; UCR = Pain (fear of getting stung); CS = Tree house; CR = Fear.
Jerry: NS = Nightgown, UCS = Sexual activity; UCR = Arousal because Mary is in the mood for sex; CS = nightgown; CR = Arousal.
Student: NS = peanuts, UCS = Plane Crash; UCS = Fear because of plane crash; CS = peanuts; CR = fear.
Friends dog: Your friend is hitting the dog with a rolled-up newspaper. NS = rolled up newspaper, UCS = Getting Hit; UCR = pain (fear) of getting hit; CS = rolled up newspaper; CR = fear.
Joan: Original Conditioning: NS = Monkeys, UCS = Attack; UCR =Pain (fear of attack); CS = monkeys; CR = fear of monkeys. Counterconditioning: UCS = Affection and Cuddling; UCR = good feeling because of affection and cuddling; CS = monkeys; CR = good feeling toward monkeys.
Bill: NS = chicken, UCS = Food poisoning; UCR = becoming sick due to poisoning; CS = chicken; CR = becoming nauseated at thought of chicken. Bill is experiencing stimulus generalisation because the turkey is very similar to his original CS of chicken. However, the duck is not similar enough to chicken to produce stimulus generalisation and therefore, Bill is experiencing stimulus discrimination with the duck.