“A Further Analysis of Reasoning in Rats: 1. The Influence of Trace-Aggregation on Problem Solving”, 1937-08 ():
When white rats were given 5 successive daily trials on the Maier 3-table reasoning test, their 3 final trials were much lower in accuracy than the two first trials. The decrease in accuracy amounted to 25.6%. Rats with cortical injuries evidenced a reduced accuracy of 42.2% after the first trials.
These results indicate that “giving several tests in succession increases the qualitative complexity of a problem.” Decreased accuracy after the second daily trial is attributed to the rats’ difficulty in choosing between the last position of a food table and its previous positions. It is only after two tables have become associated with food that such “confusion” arises.
“The Gestalt theory of memory traces is used to explain the nature of this confusion. According to this theory, similar memory traces tend to form aggregates. Repeated testing… may reduce the uniqueness of the memories of the tables in only one way. This occurs when a choice between two tables, both of which have been food tables at different times, is presented to the rat. Since on the first tests of the day the choice is between a food and a no-food table, the memory traces at this time are more unique.”