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Serial feature negative training to a target unconditioned stimulus
Behavioural Processes 47 (1999) 153 – 159 www.elsevier.com/locate/behavproc
Serial feature negative training to a target unconditioned stimulus Murray J. Goddard * Department of Psychology, Uni6ersity of New Brunswick, P.O. Box 5050, Saint John, NB, Canada E2L 4L5 Received 15 January 1999; received in revised form 7 June 1999; accepted 10 June 1999
Abstract In serial feature-negative (SFN) training to a target unconditioned stimulus (US), eight rats received two types of intermingled trials: (1) trials in which a tone was followed by the delivery of a single food pellet US, and (2) trials in which the delivery of a single food pellet US was followed by three additional food pellets. Following SFN training, the tone showed little transfer to a partially reinforced light cue and the tone’s negative modulation was eliminated after tone extinction. Implications for theories of occasion-setting are discussed. © 1999 Elsevier Science B.V. All rights reserved. Keywords: Occasion-setting; Rats; Stimulus
1. Introduction In occasion-setting, an organism must learn that a target conditioned stimulus (CS) will, or will not, be followed by an unconditioned stimulus (US) when preceded by a feature cue. For example, in a serial feature-positive (SFP) discrimination, organisms receive F−T + , T − trials and must learn that a target cue (T) is only reinforced when preceded by a feature cue (F). In a serial feature-negative (SFN) discrimination, organisms receive F−T − , T+ trials and must learn that a target cue is only reinforced when not preceded by a feature cue.
* Tel.: + 1-506-6485640; fax: + 1-506-6485780.
Normally, in occasion-setting, relatively neutral cues (such as tones or lights) serve as the feature and target cues. Recently, however, we have examined occasion-setting in which a US served as the feature cue in a SFP (Goddard and Holland, 1996) and SFN (Goddard and Holland, 1997) discrimination. The use of a US feature cue has provided important insights into modulatory learning and has uncovered some important differences between the modulatory ability of US
Fig. 1. An illustration of the experimental design.
0376-6357/99/$ - see front matter © 1999 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 6 - 6 3 5 7 ( 9 9 ) 0 0 0 6 3 - 7
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M.J. Goddard / Beha6ioural Processes 47 (1999) 153–159
and CS features (Skinner et al., 1998). For example, in a SFP discrimination, a CS feature shows occasion-setting transfer to a target trained with another CS feature (Rescorla, 1985; Holland, 1992; Schmajuk et al., 1998). However, in a SFP discrimination, a US feature shows little occasionsetting transfer to a target trained with a CS feature and a CS feature shows little occasion-setting transfer to a target trained with a US feature (Goddard and Holland, 1996). Limited occasionsetting transfer between US and CS features suggests occasion-setting transfer may be restricted to events possessing certain shared attributes (Goddard and Holland, 1996). In a SFN discrimination, the present study further explored occasion-setting in which a US served as the target (rather than feature). In a SFN discrimination, eight rats received two types of intermingled trials: (1) trials in which a tone was followed by the delivery of a single food pellet US, and (2) trials in which the delivery of a single food pellet US was followed by three additional food pellets (please see Fig. 1). The use of a SFN training procedure with a target US was theoretically interesting for several reasons. First, note that on a tone-food trial sequence, the tone must simultaneously acquire negative modulation (‘on this occasion, the single food pellet will not be followed by additional food’) and feature excitation (since the tone is itself paired with food). This importantly differs from serial feature-negative patterning (F+ , T+ , F− T− ) (for example, see Rescorla, 1991) or feature conditioning following serial feature-negative training (for example, see Holland, 1984, 1992), where the feature presumably acquires excitation on F + trials and negative modulation on F− T − trials. Thus, the present experiment provides the first test of whether a feature can simultaneously acquire excitation and negative modulation in a single trial sequence. In addition, the use of a SFN training procedure with a target US was theoretically interesting because it was possible that the feature’s negative modulation might be based upon feature excitation. Indeed, Swartzentruber has shown that the excitatory properties of a feature may importantly contribute to the solution of a SFN and SFP
discrimination (Swartzentruber, 1998; see also Rescorla, 1991). If negative modulation was importantly based upon feature excitation, in the present study, subsequent feature extinction might eliminate negative modulation. Note that the effects of feature extinction on negative modulation would be contrary to established conventions in which the effects of feature conditioning on negative modulation, or the effects of feature extinction on positive modulation, are normally examined (for example, see Holland, 1984, 1989; Morell and Holland, 1993). Finally, the use of a SFN training procedure with a target US was theoretically interesting because subsequent modulatory transfer could be examined. Recall that Goddard and Holland (1996) showed little modulatory transfer, in an operant SFP discrimination, when a US feature was paired with a target previously trained with a CS feature (or a CS feature was paired with a target previously trained with a US feature). In the present study, modulatory transfer was examined to a target CS that had been partially reinforced; any increases or decreases in an intermediate level of responding could then be measured. 2. Method
2.1. Subjects The subjects were eight individually housed female Sprague–Dawley rats obtained from the Charles River Company, St. Constant, Que., Canada. The subjects were about 120-days-old at the beginning of the experiment and had not been involved in previous research. The animal holding room was maintained on a 14–10 h, light–dark cycle with the lights on at 06:00 h and off at 20:00 h. Subjects were maintained at 80% of their ad libitum weight, by measured feedings of Purina Rat Chow at the end of a session, and had continuous access to water.
2.2. Apparatus The experimental chambers consisted of four identical boxes measuring 31× 26.5×36 cm. The
M.J. Goddard / Beha6ioural Processes 47 (1999) 153–159
two side walls were clear acrylic while the two end walls and top were aluminum. The floor consisted of 16 steel bars, each 0.5 cm in diameter, spaced approx. 1.5 cm apart. The front end wall contained a centrally located magazine, a triple cue lamp module, and a lever. The 3.5 × 4 cm magazine was recessed into the front end wall, with the bottom edge about 2 cm above the floor. A photocell circuit automatically recorded magazine entries and a solenoid operated feeder, located behind the front end wall, delivered a 45-mg dustless precision food pellet. The lever was approx. 3.5 cm wide and was located near the right edge of the front end wall and approx. 2.5 cm above the floor. The triple cue lamp module was centered 5 cm. above the lever and consisted of three lights colored red, yellow, and green. An identical triple cue lamp module was located on the right edge of the back end wall. In addition, the back end wall contained a centrally located magazine and a liquid dipper that could deliver 0.01 cc of liquid. Responses to the lever were not recorded and the triple cue lamp modules, and dipper, were not used in this experiment. Outside the chamber, and mounted above the top right corner of the front end wall, was a speaker that could deliver a 1500-Hz, 84 dB(A) tone. An open-fronted wooden cabinet, separated into four compartments, housed the chambers in a 2 ×2 design. A fan mounted on the back of each compartment provided air circulation and a constant masking noise of 66 dB. On the floor of each compartment, mounted outside the bottom left floor of the chamber, was a houselight. In addition to providing the only source of illumination, the houselight provided an additional CS when flashed at the rate of 0.2 flashes/s. A videocamera was mounted approx. 1 m in front of the chambers, encompassing all four chambers in its view. In an adjacent room was a videocassette recorder, a monitor connected to the camera, and an IBM-compatible computer that controlled the four chambers.
2.3. Procedure Subjects first received magazine training. Two food pellets were placed into the magazine (before
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a subject was put in the chamber), and subjects were simply left undisturbed for 10 min. After 10 min, 10 additional food pellets were delivered at 1.5 min interfood intervals, in the remainder of the 30-min session. After 30 min, the houselights were turned off (in all phases of this experiment, the houselights were turned off to end a session). In the next 50 sessions, subjects received SFN training to a target US. In SFN training, subjects received two types of intermingled trials: (1) trials in which a 5 s tone was followed, after 5 s, by the delivery of a single food pellet US, and (2) trials in which the delivery of a single food pellet US was followed, after 10 s, by three additional food pellets. Discrimination performance was measured by magazine entries in the 10 s interval after the delivery of the single food pellet US. In each daily 20 min session, subjects received one tone-food (T− F− ) and one food-triple food trial (F+ ), with the order counterbalanced across days according to a repeating + − − + schedule (foodtriple food trial first on day 1, tone-food trial first on days 2 and 3, and food-triple food trial first on day 4). There was a fixed 8 min delay between the beginning of a session and the first trial and between the first and second trial. Following SFN training, subjects received test sessions 1 and 2. In each daily 20 min test session, subjects received one tone-food, and one foodalone test trial, using similar parameters as used in training. Discrimination performance was measured by magazine entries in the 30 s interval after the delivery of a single food pellet. Following test sessions 1 and 2, subjects received six retraining sessions. In each retraining session, subjects received one tone-food and one food-triple food trial (as in original training), in addition to receiving one reinforced and one nonreinforced flashing houselight trial (to later measure occasion-setting transfer). On a flashing houselight trial, the flashing houselight was presented for 5 s, followed, after a 5 s delay, by either the delivery of three additional pellets (on a reinforced trial) or nothing (on a nonreinforced trial). Events were randomly ordered in each daily 20 min session, with the constraint that there was a fixed 4 min interval between the start of the session and the first event and between each event.
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Following the six retraining sessions, subjects received test sessions 3 and 4. In each test session, subjects received one of five events. These five events included a tone-food and food-alone trial (to measure original occasion-setting performance), a tone-alone and houselight-alone trial (to measure the excitatory strength of the feature and transfer target, respectively), and, of most interest, a tone-houselight trial (to measure occasion-setting transfer). Events were randomly ordered in each daily 20 min session, with the constraint that there was a fixed 3 min interval between the start of the session and the first event and between each event. Magazine entries were recorded 30 s after the delivery of a single event, or 30 s after the delivery of the second of two events. Subjects then received 10 retraining sessions (identical to the first six retraining sessions) followed by test sessions 5 and 6. Test sessions 5 and 6 were identical to test sessions 3 and 4. Following test sessions 5 and 6, the excitatory strength of the tone was extinguished. In each of five daily 20 min extinction sessions, subjects received 5 tone-alone presentations with a fixed 3 min interval between the start of the session and the first tone-alone presentation and between each tone-alone presentation. Magazine entries were recorded 30 s after each tone-alone presentation. Finally, after tone extinction, subjects received test sessions 7 and 8. Test sessions 7 and 8 were identical to test sessions 3 and 4. Nonparametric inferential statistics were used with a criterion level of P 50.05, two-tailed.
Fig. 2. Magazine entries/min in the first 50 sessions of discrimination training. Subjects received tone-food (T −F −) and food-triple food (F + ) trials. Magazine entries were recorded 10 s after a single food pellet.
subjects made at least one magazine entry simply to retrieve the food pellet on T− F− trials. Following discrimination training, subjects received two test sessions. Responding, averaged over test sessions 1 and 2, is shown in Fig. 3. In test sessions 1 and 2, subjects showed greater responding on F+, in comparison to T− F− trials; unfortunately, this difference was just short of statistical significance (T (8)= 5).
3. Results Responding during the first 50 sessions of discrimination training are shown in Fig. 2. Discrimination difference scores were small in magnitude but were reliable in the ninth (T (8)= 0) and tenth (T (7) = 0) block of training. It was likely that the 10 s time interval (to record magazine entries) prohibited showing larger differences in responding between the tone-food (T − F−) and food-triple food (F+) trials, as
Fig. 3. Average magazine entries/min in test sessions 1 and 2 to the tone-food (T − F−) and food-alone (F +) trials. Magazine entries were recorded 30 s after a single food pellet.
M.J. Goddard / Beha6ioural Processes 47 (1999) 153–159
Fig. 4. Average magazine entries/min in test sessions 3 and 4 to the tone-food (T −F − ), food-alone (F + ), tone-alone (T), tone-houselight (T-HL), and houselight-alone (HL) trials. Magazine entries were recorded 30 s after the delivery of a single event, or 30 s after the delivery of the second of two events.
Subjects then received retraining and houselight conditioning prior to test sessions 3 and 4. Responding, averaged over test sessions 3 and 4, is shown in Fig. 4. In test sessions 3 and 4, subjects showed 21.4 magazine entries/min on F +, and 8.1 magazine entries/min on T− F −, trials (T (8) =0). Responding to the tone-alone was 14.8 magazine entries/min; tone-alone responding did not differ significantly from responding on either F+ , or T− F− , trials (T’s\5). Occasion-setting transfer was not shown in test sessions 3 and 4; responding on T-HL trials was somewhat higher than responding on HL-alone trials; this difference, however, was not reliable (T (7) = 7.5). One difficulty, though, was that responding on HL-alone trials was small and any negative modulation may have been obscured by a floor effect. Therefore, all subjects were given 10 additional retraining sessions (with additional reinforced and nonreinforced houselight trials) prior to test sessions 5 and 6. Following the 10 additional retraining sessions, subjects received test sessions 5 and 6. Responding, averaged over test sessions 5 and 6, is shown in Fig. 5. In test sessions 5 and 6, subjects showed 21.3 magazine entries/min on F+, and 10.3 magazine
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entries/min on T− F−, trials (T (8) = 0). Responding to the tone-alone was 12.4 magazine entries/min; tone-alone responding was significantly lower than responding on F+ (T (8)= 2), but did not differ significantly from responding on T−F − (T (8)= 14), trials. As in test sessions 3 and 4, occasion-setting transfer continued to be absent; responding on T-HL trials did not differ significantly from HLalone trials (T (7)= 7). Following test sessions 5 and 6, the tone feature was extinguished. In extinction, responding to the tone declined from 8.0 magazine entries/min in session one to 5.4 magazine entries/min in session five (T (8)=0). Following tone extinction, subjects received two final test sessions (test sessions 7 and 8). Responding, averaged over test sessions 7 and 8, is shown in Fig. 6. Responding on the original SFN discrimination was lost after tone extinction. Subjects showed 13.5 magazine entries/min on F+ , and 13.6 magazine entries/min on T−F− , trials (T (8)= 11). Responding to the tone-alone was 3.5 magazine entries/min; tone-alone responding was significantly lower than responding on F+ (T (8)=2), and T− F− (T (8)=2), trials.
Fig. 5. Average magazine entries/min in test sessions 5 and 6 to the tone-food (T − F−), food-alone (F + ), tone-alone (T), tone-houselight (T-HL), and houselight-alone (HL) trials. Magazine entries were recorded 30 s after the delivery of a single event, or 30 s after the delivery of the second of two events.
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Fig. 6. Average magazine entries/min in test sessions 7 and 8 to the tone-food (T − F−), food-alone (F + ), tone-alone (T), tone-houselight (T-HL), and houselight-alone (HL) trials. Magazine entries were recorded 30 s after the delivery of a single event, or 30 s after the delivery of the second of two events.
As in test sessions 3 – 6, occasion-setting transfer was absent; responding on T-HL trials did not differ significantly from responding on HL-alone trials (T (8)= 13.5). 4. Discussion In the present study, the ability of a tone feature to modulate a target US was examined in a SFN discrimination. Results showed that the tone feature simultaneously acquired negative modulation and feature excitation. Further, results showed that the tone’s negative modulation did not transfer to a partially reinforced CS and, of most interest, negative modulation was completely abolished following feature extinction. Examining the effects of feature extinction on negative modulation runs contrary to established conventions in which the effects of feature conditioning on negative modulation, or the effects of feature extinction on positive modulation, are normally examined (for example, see Holland, 1984, 1989; Morell and Holland, 1993). Further, the finding that negative modulation was abolished following feature extinction supports work by Swartzentruber (1998) showing that feature excitation may importantly contribute to positive and negative modulation. In the present study, the loss
of negative modulation, with feature extinction, provides strong evidence that negative modulation was based on the feature’s own excitation in the present training regime. The important contribution of feature excitation to negative modulation in the present study may have resulted because of the unique trial sequence involved in serial feature-negative training to a target unconditioned stimulus. In serial feature-negative patterning (F+ , T + , F− T− ) (for example, see Rescorla, 1991), or feature conditioning following serial feature-negative training (for example, see Holland, 1984, 1992), the feature putatively acquires excitation on F+ trials and negative modulation on F− T− trials. However, in the present study, the tone feature could only acquire excitation and negative modulation on a tone-food trial. Thus, the acquisition of excitation and negative modulation in the same trial sequence may have especially encouraged the organism to encode feature excitation as an important component in negative modulation. Although feature extinction abolished negative modulation in the present study, it is possible that the extinction of any excitor may have abolished such modulatory control. Although there is no evidence here to rule out this alternative possibility, there is evidence from other sources that makes this alternative unattractive. For example, in an autoshaping preparation, Rescorla (1986) trained two diffuse stimuli to modulate responding to each of two keylight targets. Subsequent nonreinforced presentations of one modulator with a simple excitor disrupted that feature’s modulation but had little effect on the modulation of the untreated feature. Rescorla (1985) has also shown that a facilitator can augment responding to a target but is not itself augmented by another facilitator or target, even when facilitators and targets consisted of keylight stimuli with some possibility of generalization. These results suggest that the specific properties of a feature are encoded in modulatory training, making it unlikely that an organism would treat the extinction of the original feature, or any excitor, as equivalent operations. The failure of the tone feature to transfer either excitation or negative modulation to a partially
M.J. Goddard / Beha6ioural Processes 47 (1999) 153–159
reinforced houselight CS deserves comment. One possibility is that the failure of the tone to affect houselight responding was due to the transfer of both excitation and negative modulation. However, by this reasoning, feature extinction should have resulted in the transfer of negative modulation, which was not shown. Another possibility is that the tone’s excitation (but not negative modulation) should have shown transfer but, by this reasoning, it is difficult to explain why the tone’s excitation did not increase responding to the partially reinforced houselight on early transfer trials. Thus, it is not clear at the present time why the tone consistently failed to affect houselight responding. An interesting question for further research is whether the tone’s occasion-setting properties would transfer to other CS targets or whether transfer might be limited to other USs, or other USs trained as targets in an occasion-setting discrimination. Acknowledgements This research was supported by Grant OGP 42025 from the Natural Sciences and Engineering Research Council of Canada (NSERC).
References Goddard, M.J., Holland, P.C., 1996. Type of feature affects transfer in operant serial feature-positive discriminations. Anim. Learn. Behav. 24, 266–276.
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Goddard, M.J., Holland, P.C., 1997. The effects of feature identity in operant serial feature-negative discriminations. Learn. Motivation 28, 577 – 608. Holland, P.C., 1984. Differential effects of reinforcement of an inhibitory feature after serial and simultaneous feature negative discrimination training. J. Exp. Psychol.: Anim. Behav. Process. 10, 461 – 475. Holland, P.C., 1989. Feature extinction enhances transfer of occasion setting. Anim. Learn. Behav. 17, 269 – 279. Holland, P.C., 1992. Occasion-setting in Pavlovian conditioning. In: Medin, D. (Ed.), The Psychology of Learning and Motivation, vol. 28. Academic Press, San Diego, pp. 69 – 125. Morell, J.R., Holland, P.C., 1993. Summation and transfer of negative occasion setting. Anim. Learn. Behav. 21, 145 – 153. Rescorla, R.A., 1985. Conditioned inhibition and facilitation. In: Miller, R.R., Spear, N.E. (Eds.), Information processing in animals: conditioned inhibition. Erlbaum, Hillsdale, NJ, pp. 299 – 326. Rescorla, R.A., 1986. Extinction of facilitation. J. Exp. Psychol.: Anim. Behav. Process. 12, 16 – 24. Rescorla, R.A., 1991. Separate reinforcement can enhance the effectiveness of modulators. J. Exp. Psychol.: Anim. Behav. Process. 17, 259 – 269. Schmajuk, N.A., Lamoureux, J.A., Holland, P.C., 1998. Occasion-setting: a neural network approach. Psychol. Rev. 105, 3 – 32. Skinner, D.M, Goddard, M.J., Holland, P.C., 1998. What can nontraditional features tell us about conditioning and occasion setting? In: Schmajuk, N.A., Holland, P.C. (Eds.), Occasion Setting. Associative Learning and Cognition in Animals. American Psychological Association, Washington, DC, pp. 113 – 144. Swartzentruber, D., 1998. Perspectives on modulation: modulator- and target-focused views. In: Schmajuk, N.A., Holland, P.C. (Eds.), Occasion Setting. Associative Learning and Cognition in Animals. American Psychological Association, Washington, DC, pp. 167 – 197.
Serial feature negative training to a target unconditioned stimulus Murray J. Goddard * Department of Psychology, Uni6ersity of New Brunswick, P.O. Box 5050, Saint John, NB, Canada E2L 4L5 Received 15 January 1999; received in revised form 7 June 1999; accepted 10 June 1999
Abstract In serial feature-negative (SFN) training to a target unconditioned stimulus (US), eight rats received two types of intermingled trials: (1) trials in which a tone was followed by the delivery of a single food pellet US, and (2) trials in which the delivery of a single food pellet US was followed by three additional food pellets. Following SFN training, the tone showed little transfer to a partially reinforced light cue and the tone’s negative modulation was eliminated after tone extinction. Implications for theories of occasion-setting are discussed. © 1999 Elsevier Science B.V. All rights reserved. Keywords: Occasion-setting; Rats; Stimulus
1. Introduction In occasion-setting, an organism must learn that a target conditioned stimulus (CS) will, or will not, be followed by an unconditioned stimulus (US) when preceded by a feature cue. For example, in a serial feature-positive (SFP) discrimination, organisms receive F−T + , T − trials and must learn that a target cue (T) is only reinforced when preceded by a feature cue (F). In a serial feature-negative (SFN) discrimination, organisms receive F−T − , T+ trials and must learn that a target cue is only reinforced when not preceded by a feature cue.
* Tel.: + 1-506-6485640; fax: + 1-506-6485780.
Normally, in occasion-setting, relatively neutral cues (such as tones or lights) serve as the feature and target cues. Recently, however, we have examined occasion-setting in which a US served as the feature cue in a SFP (Goddard and Holland, 1996) and SFN (Goddard and Holland, 1997) discrimination. The use of a US feature cue has provided important insights into modulatory learning and has uncovered some important differences between the modulatory ability of US
Fig. 1. An illustration of the experimental design.
0376-6357/99/$ - see front matter © 1999 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 6 - 6 3 5 7 ( 9 9 ) 0 0 0 6 3 - 7
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M.J. Goddard / Beha6ioural Processes 47 (1999) 153–159
and CS features (Skinner et al., 1998). For example, in a SFP discrimination, a CS feature shows occasion-setting transfer to a target trained with another CS feature (Rescorla, 1985; Holland, 1992; Schmajuk et al., 1998). However, in a SFP discrimination, a US feature shows little occasionsetting transfer to a target trained with a CS feature and a CS feature shows little occasion-setting transfer to a target trained with a US feature (Goddard and Holland, 1996). Limited occasionsetting transfer between US and CS features suggests occasion-setting transfer may be restricted to events possessing certain shared attributes (Goddard and Holland, 1996). In a SFN discrimination, the present study further explored occasion-setting in which a US served as the target (rather than feature). In a SFN discrimination, eight rats received two types of intermingled trials: (1) trials in which a tone was followed by the delivery of a single food pellet US, and (2) trials in which the delivery of a single food pellet US was followed by three additional food pellets (please see Fig. 1). The use of a SFN training procedure with a target US was theoretically interesting for several reasons. First, note that on a tone-food trial sequence, the tone must simultaneously acquire negative modulation (‘on this occasion, the single food pellet will not be followed by additional food’) and feature excitation (since the tone is itself paired with food). This importantly differs from serial feature-negative patterning (F+ , T+ , F− T− ) (for example, see Rescorla, 1991) or feature conditioning following serial feature-negative training (for example, see Holland, 1984, 1992), where the feature presumably acquires excitation on F + trials and negative modulation on F− T − trials. Thus, the present experiment provides the first test of whether a feature can simultaneously acquire excitation and negative modulation in a single trial sequence. In addition, the use of a SFN training procedure with a target US was theoretically interesting because it was possible that the feature’s negative modulation might be based upon feature excitation. Indeed, Swartzentruber has shown that the excitatory properties of a feature may importantly contribute to the solution of a SFN and SFP
discrimination (Swartzentruber, 1998; see also Rescorla, 1991). If negative modulation was importantly based upon feature excitation, in the present study, subsequent feature extinction might eliminate negative modulation. Note that the effects of feature extinction on negative modulation would be contrary to established conventions in which the effects of feature conditioning on negative modulation, or the effects of feature extinction on positive modulation, are normally examined (for example, see Holland, 1984, 1989; Morell and Holland, 1993). Finally, the use of a SFN training procedure with a target US was theoretically interesting because subsequent modulatory transfer could be examined. Recall that Goddard and Holland (1996) showed little modulatory transfer, in an operant SFP discrimination, when a US feature was paired with a target previously trained with a CS feature (or a CS feature was paired with a target previously trained with a US feature). In the present study, modulatory transfer was examined to a target CS that had been partially reinforced; any increases or decreases in an intermediate level of responding could then be measured. 2. Method
2.1. Subjects The subjects were eight individually housed female Sprague–Dawley rats obtained from the Charles River Company, St. Constant, Que., Canada. The subjects were about 120-days-old at the beginning of the experiment and had not been involved in previous research. The animal holding room was maintained on a 14–10 h, light–dark cycle with the lights on at 06:00 h and off at 20:00 h. Subjects were maintained at 80% of their ad libitum weight, by measured feedings of Purina Rat Chow at the end of a session, and had continuous access to water.
2.2. Apparatus The experimental chambers consisted of four identical boxes measuring 31× 26.5×36 cm. The
M.J. Goddard / Beha6ioural Processes 47 (1999) 153–159
two side walls were clear acrylic while the two end walls and top were aluminum. The floor consisted of 16 steel bars, each 0.5 cm in diameter, spaced approx. 1.5 cm apart. The front end wall contained a centrally located magazine, a triple cue lamp module, and a lever. The 3.5 × 4 cm magazine was recessed into the front end wall, with the bottom edge about 2 cm above the floor. A photocell circuit automatically recorded magazine entries and a solenoid operated feeder, located behind the front end wall, delivered a 45-mg dustless precision food pellet. The lever was approx. 3.5 cm wide and was located near the right edge of the front end wall and approx. 2.5 cm above the floor. The triple cue lamp module was centered 5 cm. above the lever and consisted of three lights colored red, yellow, and green. An identical triple cue lamp module was located on the right edge of the back end wall. In addition, the back end wall contained a centrally located magazine and a liquid dipper that could deliver 0.01 cc of liquid. Responses to the lever were not recorded and the triple cue lamp modules, and dipper, were not used in this experiment. Outside the chamber, and mounted above the top right corner of the front end wall, was a speaker that could deliver a 1500-Hz, 84 dB(A) tone. An open-fronted wooden cabinet, separated into four compartments, housed the chambers in a 2 ×2 design. A fan mounted on the back of each compartment provided air circulation and a constant masking noise of 66 dB. On the floor of each compartment, mounted outside the bottom left floor of the chamber, was a houselight. In addition to providing the only source of illumination, the houselight provided an additional CS when flashed at the rate of 0.2 flashes/s. A videocamera was mounted approx. 1 m in front of the chambers, encompassing all four chambers in its view. In an adjacent room was a videocassette recorder, a monitor connected to the camera, and an IBM-compatible computer that controlled the four chambers.
2.3. Procedure Subjects first received magazine training. Two food pellets were placed into the magazine (before
155
a subject was put in the chamber), and subjects were simply left undisturbed for 10 min. After 10 min, 10 additional food pellets were delivered at 1.5 min interfood intervals, in the remainder of the 30-min session. After 30 min, the houselights were turned off (in all phases of this experiment, the houselights were turned off to end a session). In the next 50 sessions, subjects received SFN training to a target US. In SFN training, subjects received two types of intermingled trials: (1) trials in which a 5 s tone was followed, after 5 s, by the delivery of a single food pellet US, and (2) trials in which the delivery of a single food pellet US was followed, after 10 s, by three additional food pellets. Discrimination performance was measured by magazine entries in the 10 s interval after the delivery of the single food pellet US. In each daily 20 min session, subjects received one tone-food (T− F− ) and one food-triple food trial (F+ ), with the order counterbalanced across days according to a repeating + − − + schedule (foodtriple food trial first on day 1, tone-food trial first on days 2 and 3, and food-triple food trial first on day 4). There was a fixed 8 min delay between the beginning of a session and the first trial and between the first and second trial. Following SFN training, subjects received test sessions 1 and 2. In each daily 20 min test session, subjects received one tone-food, and one foodalone test trial, using similar parameters as used in training. Discrimination performance was measured by magazine entries in the 30 s interval after the delivery of a single food pellet. Following test sessions 1 and 2, subjects received six retraining sessions. In each retraining session, subjects received one tone-food and one food-triple food trial (as in original training), in addition to receiving one reinforced and one nonreinforced flashing houselight trial (to later measure occasion-setting transfer). On a flashing houselight trial, the flashing houselight was presented for 5 s, followed, after a 5 s delay, by either the delivery of three additional pellets (on a reinforced trial) or nothing (on a nonreinforced trial). Events were randomly ordered in each daily 20 min session, with the constraint that there was a fixed 4 min interval between the start of the session and the first event and between each event.
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Following the six retraining sessions, subjects received test sessions 3 and 4. In each test session, subjects received one of five events. These five events included a tone-food and food-alone trial (to measure original occasion-setting performance), a tone-alone and houselight-alone trial (to measure the excitatory strength of the feature and transfer target, respectively), and, of most interest, a tone-houselight trial (to measure occasion-setting transfer). Events were randomly ordered in each daily 20 min session, with the constraint that there was a fixed 3 min interval between the start of the session and the first event and between each event. Magazine entries were recorded 30 s after the delivery of a single event, or 30 s after the delivery of the second of two events. Subjects then received 10 retraining sessions (identical to the first six retraining sessions) followed by test sessions 5 and 6. Test sessions 5 and 6 were identical to test sessions 3 and 4. Following test sessions 5 and 6, the excitatory strength of the tone was extinguished. In each of five daily 20 min extinction sessions, subjects received 5 tone-alone presentations with a fixed 3 min interval between the start of the session and the first tone-alone presentation and between each tone-alone presentation. Magazine entries were recorded 30 s after each tone-alone presentation. Finally, after tone extinction, subjects received test sessions 7 and 8. Test sessions 7 and 8 were identical to test sessions 3 and 4. Nonparametric inferential statistics were used with a criterion level of P 50.05, two-tailed.
Fig. 2. Magazine entries/min in the first 50 sessions of discrimination training. Subjects received tone-food (T −F −) and food-triple food (F + ) trials. Magazine entries were recorded 10 s after a single food pellet.
subjects made at least one magazine entry simply to retrieve the food pellet on T− F− trials. Following discrimination training, subjects received two test sessions. Responding, averaged over test sessions 1 and 2, is shown in Fig. 3. In test sessions 1 and 2, subjects showed greater responding on F+, in comparison to T− F− trials; unfortunately, this difference was just short of statistical significance (T (8)= 5).
3. Results Responding during the first 50 sessions of discrimination training are shown in Fig. 2. Discrimination difference scores were small in magnitude but were reliable in the ninth (T (8)= 0) and tenth (T (7) = 0) block of training. It was likely that the 10 s time interval (to record magazine entries) prohibited showing larger differences in responding between the tone-food (T − F−) and food-triple food (F+) trials, as
Fig. 3. Average magazine entries/min in test sessions 1 and 2 to the tone-food (T − F−) and food-alone (F +) trials. Magazine entries were recorded 30 s after a single food pellet.
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Fig. 4. Average magazine entries/min in test sessions 3 and 4 to the tone-food (T −F − ), food-alone (F + ), tone-alone (T), tone-houselight (T-HL), and houselight-alone (HL) trials. Magazine entries were recorded 30 s after the delivery of a single event, or 30 s after the delivery of the second of two events.
Subjects then received retraining and houselight conditioning prior to test sessions 3 and 4. Responding, averaged over test sessions 3 and 4, is shown in Fig. 4. In test sessions 3 and 4, subjects showed 21.4 magazine entries/min on F +, and 8.1 magazine entries/min on T− F −, trials (T (8) =0). Responding to the tone-alone was 14.8 magazine entries/min; tone-alone responding did not differ significantly from responding on either F+ , or T− F− , trials (T’s\5). Occasion-setting transfer was not shown in test sessions 3 and 4; responding on T-HL trials was somewhat higher than responding on HL-alone trials; this difference, however, was not reliable (T (7) = 7.5). One difficulty, though, was that responding on HL-alone trials was small and any negative modulation may have been obscured by a floor effect. Therefore, all subjects were given 10 additional retraining sessions (with additional reinforced and nonreinforced houselight trials) prior to test sessions 5 and 6. Following the 10 additional retraining sessions, subjects received test sessions 5 and 6. Responding, averaged over test sessions 5 and 6, is shown in Fig. 5. In test sessions 5 and 6, subjects showed 21.3 magazine entries/min on F+, and 10.3 magazine
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entries/min on T− F−, trials (T (8) = 0). Responding to the tone-alone was 12.4 magazine entries/min; tone-alone responding was significantly lower than responding on F+ (T (8)= 2), but did not differ significantly from responding on T−F − (T (8)= 14), trials. As in test sessions 3 and 4, occasion-setting transfer continued to be absent; responding on T-HL trials did not differ significantly from HLalone trials (T (7)= 7). Following test sessions 5 and 6, the tone feature was extinguished. In extinction, responding to the tone declined from 8.0 magazine entries/min in session one to 5.4 magazine entries/min in session five (T (8)=0). Following tone extinction, subjects received two final test sessions (test sessions 7 and 8). Responding, averaged over test sessions 7 and 8, is shown in Fig. 6. Responding on the original SFN discrimination was lost after tone extinction. Subjects showed 13.5 magazine entries/min on F+ , and 13.6 magazine entries/min on T−F− , trials (T (8)= 11). Responding to the tone-alone was 3.5 magazine entries/min; tone-alone responding was significantly lower than responding on F+ (T (8)=2), and T− F− (T (8)=2), trials.
Fig. 5. Average magazine entries/min in test sessions 5 and 6 to the tone-food (T − F−), food-alone (F + ), tone-alone (T), tone-houselight (T-HL), and houselight-alone (HL) trials. Magazine entries were recorded 30 s after the delivery of a single event, or 30 s after the delivery of the second of two events.
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Fig. 6. Average magazine entries/min in test sessions 7 and 8 to the tone-food (T − F−), food-alone (F + ), tone-alone (T), tone-houselight (T-HL), and houselight-alone (HL) trials. Magazine entries were recorded 30 s after the delivery of a single event, or 30 s after the delivery of the second of two events.
As in test sessions 3 – 6, occasion-setting transfer was absent; responding on T-HL trials did not differ significantly from responding on HL-alone trials (T (8)= 13.5). 4. Discussion In the present study, the ability of a tone feature to modulate a target US was examined in a SFN discrimination. Results showed that the tone feature simultaneously acquired negative modulation and feature excitation. Further, results showed that the tone’s negative modulation did not transfer to a partially reinforced CS and, of most interest, negative modulation was completely abolished following feature extinction. Examining the effects of feature extinction on negative modulation runs contrary to established conventions in which the effects of feature conditioning on negative modulation, or the effects of feature extinction on positive modulation, are normally examined (for example, see Holland, 1984, 1989; Morell and Holland, 1993). Further, the finding that negative modulation was abolished following feature extinction supports work by Swartzentruber (1998) showing that feature excitation may importantly contribute to positive and negative modulation. In the present study, the loss
of negative modulation, with feature extinction, provides strong evidence that negative modulation was based on the feature’s own excitation in the present training regime. The important contribution of feature excitation to negative modulation in the present study may have resulted because of the unique trial sequence involved in serial feature-negative training to a target unconditioned stimulus. In serial feature-negative patterning (F+ , T + , F− T− ) (for example, see Rescorla, 1991), or feature conditioning following serial feature-negative training (for example, see Holland, 1984, 1992), the feature putatively acquires excitation on F+ trials and negative modulation on F− T− trials. However, in the present study, the tone feature could only acquire excitation and negative modulation on a tone-food trial. Thus, the acquisition of excitation and negative modulation in the same trial sequence may have especially encouraged the organism to encode feature excitation as an important component in negative modulation. Although feature extinction abolished negative modulation in the present study, it is possible that the extinction of any excitor may have abolished such modulatory control. Although there is no evidence here to rule out this alternative possibility, there is evidence from other sources that makes this alternative unattractive. For example, in an autoshaping preparation, Rescorla (1986) trained two diffuse stimuli to modulate responding to each of two keylight targets. Subsequent nonreinforced presentations of one modulator with a simple excitor disrupted that feature’s modulation but had little effect on the modulation of the untreated feature. Rescorla (1985) has also shown that a facilitator can augment responding to a target but is not itself augmented by another facilitator or target, even when facilitators and targets consisted of keylight stimuli with some possibility of generalization. These results suggest that the specific properties of a feature are encoded in modulatory training, making it unlikely that an organism would treat the extinction of the original feature, or any excitor, as equivalent operations. The failure of the tone feature to transfer either excitation or negative modulation to a partially
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reinforced houselight CS deserves comment. One possibility is that the failure of the tone to affect houselight responding was due to the transfer of both excitation and negative modulation. However, by this reasoning, feature extinction should have resulted in the transfer of negative modulation, which was not shown. Another possibility is that the tone’s excitation (but not negative modulation) should have shown transfer but, by this reasoning, it is difficult to explain why the tone’s excitation did not increase responding to the partially reinforced houselight on early transfer trials. Thus, it is not clear at the present time why the tone consistently failed to affect houselight responding. An interesting question for further research is whether the tone’s occasion-setting properties would transfer to other CS targets or whether transfer might be limited to other USs, or other USs trained as targets in an occasion-setting discrimination. Acknowledgements This research was supported by Grant OGP 42025 from the Natural Sciences and Engineering Research Council of Canada (NSERC).
References Goddard, M.J., Holland, P.C., 1996. Type of feature affects transfer in operant serial feature-positive discriminations. Anim. Learn. Behav. 24, 266–276.
.
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Goddard, M.J., Holland, P.C., 1997. The effects of feature identity in operant serial feature-negative discriminations. Learn. Motivation 28, 577 – 608. Holland, P.C., 1984. Differential effects of reinforcement of an inhibitory feature after serial and simultaneous feature negative discrimination training. J. Exp. Psychol.: Anim. Behav. Process. 10, 461 – 475. Holland, P.C., 1989. Feature extinction enhances transfer of occasion setting. Anim. Learn. Behav. 17, 269 – 279. Holland, P.C., 1992. Occasion-setting in Pavlovian conditioning. In: Medin, D. (Ed.), The Psychology of Learning and Motivation, vol. 28. Academic Press, San Diego, pp. 69 – 125. Morell, J.R., Holland, P.C., 1993. Summation and transfer of negative occasion setting. Anim. Learn. Behav. 21, 145 – 153. Rescorla, R.A., 1985. Conditioned inhibition and facilitation. In: Miller, R.R., Spear, N.E. (Eds.), Information processing in animals: conditioned inhibition. Erlbaum, Hillsdale, NJ, pp. 299 – 326. Rescorla, R.A., 1986. Extinction of facilitation. J. Exp. Psychol.: Anim. Behav. Process. 12, 16 – 24. Rescorla, R.A., 1991. Separate reinforcement can enhance the effectiveness of modulators. J. Exp. Psychol.: Anim. Behav. Process. 17, 259 – 269. Schmajuk, N.A., Lamoureux, J.A., Holland, P.C., 1998. Occasion-setting: a neural network approach. Psychol. Rev. 105, 3 – 32. Skinner, D.M, Goddard, M.J., Holland, P.C., 1998. What can nontraditional features tell us about conditioning and occasion setting? In: Schmajuk, N.A., Holland, P.C. (Eds.), Occasion Setting. Associative Learning and Cognition in Animals. American Psychological Association, Washington, DC, pp. 113 – 144. Swartzentruber, D., 1998. Perspectives on modulation: modulator- and target-focused views. In: Schmajuk, N.A., Holland, P.C. (Eds.), Occasion Setting. Associative Learning and Cognition in Animals. American Psychological Association, Washington, DC, pp. 167 – 197.