Matching to sample

In animal psychology, matching-to-sample refers to a specific experimental set-up with which memory functions are examined. The English term is also adopted in the German language and roughly means "to select the correct selection option corresponding to the example stimulus".

Simultaneous matching-to-sample

With simultaneous matching-to-sample , the example and target stimuli are presented at the same time.

example

Matching-to-sample experiments were especially popular with pigeons . The simplest experimental setup is shown in the following example: There are three small, illuminated buttons in front of the pigeon. The central button is illuminated in green. The outer buttons are also illuminated, with one also appearing green and the other a different color. It only receives an appetizing amplifier if it picks on the outer button that is the same color as the central one (here: green). The button in the middle represents the sample stimulus , according to which the pigeon must orient itself in its picking reaction. The outer button that has the same color as the example stimulus is called the target stimulus . The pigeon has to peck at him in order to be reinforced. Other stimuli presented together with the target stimulus are called distractor stimuli ( i.e. distraction stimuli , because the pigeon makes a mistake when it picks on them).

research object

The above experimental set-up represents an example of simultaneous matching-to-sample . Such experiments are used in particular to examine the discrimination limits of the organisms. For example, colored lights differ in their wavelength. One can now adjust the wavelengths of the example and target stimuli more and more until the pigeon can no longer distinguish between the two. In this way one can determine which wavelength differences of visible light a pigeon can still perceive. Such experiments also make it possible to find out which objects an organism can distinguish. For example, pigeons can not only distinguish between images of animals, things like tables and chairs, and human faces - they can even discriminate against the same faces with different moods. Another object of investigation is the generalization ability of organisms. So it is of interest how well organisms can transfer from one stimulus to another. For example, pigeons were shown as sample stimuli in various photographs on which water was depicted in some form (be it as a lake, as rain, as a stream, etc.). As target stimuli, new pictures were offered to the pigeon, on which water was also shown. Pigeons can recognize photographs with water very well and, for example, distinguish them well from pictures with blue tarpaulins or blue sky.

Delayed matching-to-sample

In a delayed matching-to-sample task, the sample and target stimuli are not presented simultaneously, but with a time delay ( delay: delay ). Thus memory functions can be examined.

example

There are three illuminated buttons in front of a dove. (As a rule, in animal experiments, the middle button is first briefly illuminated and the pigeon waits for it to peck to ensure that the pigeon directs its attention to the buttons.) The example stimulus is presented on the middle button. Then this is turned off for a certain period of time. After this interval, the two outer buttons are illuminated with the target and a distractor stimulus and the pigeon has to pick on the target stimulus, which must correspond to the example stimulus, in order to be amplified.

research object

The insertion of a time interval between the example and target stimulus enables the investigation of memory performance and function. It was observed that the proportion of correct matching decisions successively decreases as the time interval between the stimuli increases. At the same time, however, there is an interesting limitation of this finding: Different groups of pigeons were examined. During the training phase, the time interval between the example and target stimuli lasted differently in each of the experimental groups (between 2s and 20s). For a group, however, it was always the same. After that, test phases were carried out with the pigeons, in which the time interval from run to run was extended from 2s to 20s. According to the research results above, one would have to expect that the matching performance would generally deteriorate as the interval increases. However, it was observed that the time interval at which the pigeons showed the best performance was not the shortest, but the interval that was also used in training. If the pigeons were trained with a time interval of 10s between the stimuli, they showed the best matching performance at the 10s interval.

Another experimental variation of matching demonstrates deliberate forgetting (cued forgetting).