It is quite possible, then, that prior exposure to a pair cues might reduce the associability of each of them, but that performance on a discrimination task could be enhanced if the preexposure also engaged some other learning process that enabled the animal to tell them apart better.
My own attempt to do this (Hall, 2003) took as its starting point the observation that formal theories of learning, such as the Pearce-Hall (1980) model had two parameters associated with the stimulus (or at least with the CS): The associability parameter (discussed previously) and a salience parameter (S), the value of which was set by the intensity of the stimulus.
What is need for the future, therefore, is a precise specification of the (different) learning rules that govern changes in associability and in salience.
Whether the specific mechanism by which repeated exposure leads to retarded acquisition is loss of associability
, learned unattention or learned safety, cannot be decided based in our results and this is a theoretical issue that is beyond our present purposes.
According to that view, preexposure to spatial stimuli should affect their associability in a similar way to other stimuli--like tones and lights--routinely employed as conditioned or discriminative stimuli in standard classical and instrumental conditioning tasks.
However, when the subjects face a harder discriminative task, that is when they have to learn a discrimination between two similar stimuli sharing many features in common, preexposure facilities subsequent learning--a perceptual learning effect--due to the differential loss of associability between the common and the unique features of the stimuli (McLaren & Mackintosh, 2000).
When preexposure was to the intermediate ann, loss of associability should affect the elements common to the two locations between which the animal had to discriminate, thus increasing their discriminability.
Bingman, Jones, Strasser, Gagliardo, & Ioale, 1995) have suggested that the deficit in associability of sun-compass derived directional information may in turn account for the impairment of hippocampal pigeons in establishing the navigational map.
The work of Bingman and his colleagues leads to the following conclusions: first, the navigational map of homing pigeons is not located in the hippocampal formation; second, hippocampal pigeons show an impairment in the associability of sun-compass information, an impairment that may be the cause of the impaired acquisition of the navigational map seen in them; third, hippocampal pigeons rely more than intact birds upon specific local cues as opposed to more global distal 'location' cues.
More generally, the conclusion is that the impairments seen in navigation are not limited to 'spatial' impairments: although the hippocampal birds may show a shift in reliance from global to local cues, the impairment in associability of sun-compass information does not seem specifically spatial.
1975) A theory of attention: Variations in the associability
of stimuli with reinforcement.
A theory of attention: Variations of the associability
of stimuli with reinforcement.