Generality of interference by tonal stimuli in recognition memory for pitch

An investigation was made into the disruptive effects on pitch recognition produced by tones taken from beyond the octave from which the standard (S) and comparison (C) tones were taken. Pitch recognition was required after a retention interval during which eight other tones were played. Errors were compared for sequences in which the interpolated tones were taken from the same octave as were the S and C tones; in which they were taken from the octave above; in which they were taken from the octave below; and in which half of the intervening tones were taken from the octave above and the other half from the octave below, the order of choice of octave within the sequence being random. Large disruptive effects were produced by interpolated tones drawn from the higher and lower octaves, though these effects were slightly less than those produced by tones drawn from the same octave. The greatest disruptive effect occurred when the intervening tones in any one sequence were drawn from both the higher and the lower octaves. The implications of these findings are discussed.     

Improvement in memory with time

Groups of rats which had incompletely learnt to escape from shock into the lit arm of a Y-maze, were tested for retention of the habit at various times after training. These times ranged from 30 min. to 17 days. Retention was found to be poor from 30 min. to 5 days, showed a marked improvement at 7 to 10 days and a subsequent decrement after 14 days. These results parallel those previously found for the differential susceptibility to cholinergic drugs of habits of different age. They provide further evidence that memory strength increases with time up to a point, and then gradually decreases.     

The Hull-Leeper drive discrimination situation-a control experiment

An experiment was conducted testing the author's explanation of the discrepancy between results obtained by Hull and Leeper in a similar situation. Animals were run either hungry or thirsty to obtain the appropriate reward by making one response when hungry and another when thirsty. For all groups the reward was in the same goal-box. The first group (Leeper) had the goal-box divided with each side being accessible only if the animal had made the correct response initially. The second group (Hull) had the same goal-box for both rewards, but if the wrong path was taken the animal was prevented from reaching the goal by a block. The third group had the same goal-box for both rewards again, but the animal could reach the goal-box even if the wrong path was taken and discovered the unwanted reward in the goal-box. The results confirm the predictions made from the author's theory.