Positive and negative patterning after CS preexposure in flavor aversion conditioning

Abstract

Three experiments examined rats' ability to discriminate a compound conditioned stimulus (CS) from the individual elements of that compound in a flavor aversion conditioning paradigm. In Experiment 1, presentations of a compound of sucrose and saline solutions were followed by lithium chloride injections, but presentations of those elements individually were nonreinforced (positive patterning). Conversely, in Experiments 2 and 3, presentations of the individual elements were followed by lithium chloride injection, but compound presentations were nonreinforced (negative patterning). The discriminations were acquired in all three experiments. In addition, all three experiments investigated the effects of preexposure of the discriminative stimuli on subsequent acquisition of the patterned discriminations. In positive patterning, preexposure had no measurable effect on the acquisition of responding (suppression) to the reinforced compound stimulus, but slowed the loss of suppression to the nonreinforced elements. In negative patterning, preexposure slowed the acquisition of suppression to the reinforced elements but had little effect on the loss of suppression to the nonreinforced compound.

Spontaneous configuring in conditioned flavor aversion.

“…Within the context of flavor aversion conditioning, 20 con-ditioning trials is a substantial number. Further, Forbes and Holland (1980) noted substantial compound-element differentiation in patterned discriminations in as few as three compound presentations.…”

“…Conversely, Experiments 1 A , 1 B , and 4 found no evidence for spontaneous compound-element differentiation after extended reinforced presentations of a compound stimulus. Although it is possible that more training would generate such differentiation, it is worth noting that 36 flavor-toxin pairings represent considerable training, especially considering that patterned discriminations in this preparation are acquired in as few as three presentations of the compound (Forbes & Holland, 1980). Further, in Experiment 3 the compound-element differentiation engendered by nonreinforced exposure to the compound was destroyed by subsequent extended reinforced presentation of that compound.…”

“…In apparent contradiction to this summation assumption are observations that under certain circumstances animals can respond to a stimulus compound quite differently than they respond to the separate elements of that compound. For example, animals can be taught to respond to a reinforced stimulus compound (AB) but withhold responding to the separately nonreinforced elements (A and B) of that compound, or to respond to A or B when those elements are reinforced separately but not when they are presented together and nonreinforced (e.g., Forbes & Holland, 1980; Rescorla, 1972, 1979; Woodbury, 1943).…”

“…The experiments reported here examined the effects of the extended presentation of compound stimuli on compound-element differentiation in flavor aversion conditioning in rat subjects. We chose this preparation because previous evidence indicated that rats readily learn to differentiate a compound from its elements in patterned discriminations of the form AB+, A−, B− or A+, B+, AB− (Forbes & Holland, 1980). Experiment 1 examined the effects of extended reinforced compound presentations on compound-element differentiation.…”

Evidence for a unique cue in positive patterning

“…For example, animals can be taught to respond to a consistently reinforced compound stimulus (AB) but to withhold responding to the separately nonreinforced elements (A and B) of that compound, or to respond to the separately reinforced elements A and B but to withhold responding to the nonreinforced compound AB (e.g., Forbes & Holland, 1980;Rescorla, 1972;Woodbury, 1943). Similarly, there have been several recent reports (e.g., Forbes, 1981; Gillette & Bellingham, 1982) that extended nondifferential experience with stimulus compounds may also result in progressive behavioral differentiation of the compound and its separate elements.…”