Selective associations in one-day-old rats: taste-toxicosis and texture-shock aversion learning

One-day-old rats learned aversions to a novel taste paired with lithium-induced distress and to a tactile stimulus paired with brief electric shocks. However, aversions did not develop when taste was paired with shock or when the tactile stimulus was paired with lithium treatment. The aversions occurred only when lithium treatment immediately followed taste exposure and when shock was concurrent with exposure to the tactile stimulus. These findings indicate that selective associations in aversion learning are mediated by innate mechanisms that govern conditioning in the absence of extensive ontogenetic experience. The present research also shows that selective associations are sufficient for the occurrence of long-delay learning.     

Disrupting the conditioned stimulus preexposure effect in flavor-aversion learning: effects of interoceptive distractor manipulations

Rats exposed to a flavor prior to a conditioning trial involving that stimulus learn a significantly diminished flavor aversion relative to nonpreexposed control animals. A series of four experiments investigated the ability of the conditioned stimulus (CS) preexposure effect to be disrupted by the introduction of a distractor flavor stimulus between the preexposure and conditioning episodes. Experiment 1 demonstrated that the preexposure effect could be reduced by a distractor presented immediately following the preexposure. In Experiment 2, it was discovered that a novel distractor was more effective than a familiar distractor, even though both stimuli were sensorily equivalent. Experiment 3 further analyzed the distractor effect and demonstrated that the magnitude of disruption was more pronounced with immediate than with delayed (3 hr) distractor manipulations. Finally, Experiment 4 assessed the effects of the distractor in the absence of CS preexposure. The relation of the results from these experiments to general information theory is discussed.     

Note on aversion learning to the shape of food by monkeys

Vervet and grivet monkeys were repeatedly tested eating bar- and circle-shaped cookies. One subject was always injected with lithium immediately after eating cookies with the circle shape and learned to avoid the circular cookies while continuing to eat the bar-shaped cookies. Another subject received similar treatment except that lithium injections were always delayed 30 minutes after access to the circle-shaped cookies. She also acquired a discriminative aversion. Aversion learning was not observed with 60-minute delayed toxicosis or with lithium injections administered unpaired with access to the cookies. The two types of cookies differed only in shape, and conditioning and test sessions were conducted in total darkness to preclude the use of visual cues. Therefore, the avoidance observed in subjects conditioned with immediate and 30-minute delayed toxicosis represents a conditioned aversion to the shape of the cookies as revealed by tactile cues. These findings illustrate that monkeys can learn to select food on the basis of tactile stimuli when such stimuli are conditioned with delayed aversive stimulation.