discrimination and categorisation Flashcards
what is successive discrimination
present one of the stimuli and see how the animal responds
• One at a time
what is simultaneous discrimination
present two stimuli and see which the animal approaches
• Easier, two things you discriminate between occurs together. Easier because you can compare
what is conditional discrimination
reinforce different responses (or different stimulus-response associations) in the presence of different stimuli
• E.g. blue and yellow circle. Need to go for blue circle with sound. When theres a light, yellow circle.
Examples of apparatus used for discrimination
– Discrimination boxes (mazes with discriminative stimuli added)
– Lashley’s jumping stand
– Harlow’s Wisconsin General Test Apparatus (WGTA)
– Skinner boxes in many variants
– Use of colour slides, video and computer displays, and touch screens
what is generalisation
some response occurs to stimuli that are physically similar to S+ but not identical to it
what is Generalization decrement
response to other stimuli is less than that to S+ itself; a graph relating generalized responding to values on a stimulus dimension is called a generalization gradient
what is Peak shift
Responding may be greater to a stimulus other than S+ (S’), on the “other side” of S+ from S- on the stimulus dimension
what is Transposition
If a discrimination between S+ and S- is trained, and then S’ is tested vs. S+, S’ may be chosen
what does Transfer along a continuum (TAC) mean
Training an easy discrimination on a dimension can help the animal acquire a difficult one more than simply practicing that difficult discrimination
how did Hanson et al 1959 demonstrate peak shift
• Just S+
o Gave pigeons projective key light. The black curve shows this. The pigeon learns to love the key light so pecks at it
o As you get to red or blue, generalisation decrement occurs
• S+ and S-
o In the dash line curve, the s+ (same as before) and now a s- too. This is yellower than the s+
o They trained the discrimination and were then tested
o The peak of s+ has a shifted value away from s-
o This is a peak shift
o Narrower, sharper generalisation gradient
Interacting excitatory and inhibitory generalisation gradients produce the result - as long as their shape is chosen correctly.
Excitatory and inhibitory gradients explains this phenomenon.
The theory makes the prediction that peak shift works best with similar (near) S+ and S- (true) and that the shift is greatest in this case (also true).
what did Wills and Mackintosh’s 1998 study on artificial experiment w pigeons
The icons were in fact white on black in the experiment, not black on white as shown here. The experiment was performed with pigeons.
Their results showed that a good peak-shift could be obtained with an artificial dimension constructed in this way.
How do humans show peak shift
Humans also show peak-shift, which could have consequences for choice behaviour.
What did Wills and Mackintosh 1999 show about transposition
Ps are shifted to two different gradients: the near ones (similar shades) and the far ones.
On the near discrimination there is a transposition ratio of about .75. They choose darker most of the time.
There is a drop off in the far condition. It should be just as easy as the near.
In the light condition, they solve the near one- they are transposed to the new discrimination. But at the far one, they have gone down to 0.55, barely choosing one stimulus over the other.
who first explored transfer along a continuum
Lawrence 1952 using rats
how did Lawrence 1952 explore transfer along a continuum
E+ and E- have a great difference at each end of the spectrum. It is easy to know which stimuli to go to. When transferred to H+ and H-, the grap between the H’s above the 3rd grey is much greater than the gap between the Es.
Therefore, those trained for E had a better understanding.
Training on the easy problem (E+ vs. E-) exploits the bigger difference between the curves for this problem. Training on the hard problem gives hardly any difference between H+ and H- (lots of generalisation), that’s why it’s hard!
