• Three animals (F3, F6, G13) developed high levels of accuracy and showed rapid acquisition during baseline sessions. • Three animals (F3, F6, G13) have shown high levels of accuracy during novel probes and four (F3, F6, G13, G8) during novel stimulus combinations. Impressively, these accurate performances occurred despite highly variable spatial configurations of stimuli (18 different positions) made possible by the arena apparatus.

• Performance during Novel Probes and Combinations appears to improve across exemplars of the identity relation.• Number of sessions to criterion during baseline stimulus sets decreases as a function of training.

• One animal (G8) is currently in advanced Identity MTS training and testing phases and beginning to show evidence of accurate matching during novel probes and combinations. • One animal (H8) acquired only one baseline discrimination (set A), and completed only one Probe phase (set B,C,D).

• While individual differences are apparent, some subjects have rapidly learned the MTS discriminations and transferred responding to novel stimuli - providing evidence of generalized MTS with olfactory stimuli and systematic replication of Peňa et al. (2006).

• Currently, the most advanced subjects (F3, F6, G13) are being further tested for more complex relations (arbitrary MTS, stimulus equivalence).

• The contribution of class-consistent reinforcement (sucrose or sucrose/grain pellets) on class formation and equivalence relations is also being evaluated in these on-going, advanced stages.

MTS Procedures• Subjects were presented a sample stimulus followed by multiple comparison stimuli.• Responses to the comparison (S+) identical to the sample were always reinforced; responses to the dissimilar comparison (S-) were never reinforced. • Responses were defined as any displacement of the lid from the cup rim using the front paws, snout, or face.• After lid removal, subjects were required to dig in the scented sand to retrieve buried reinforcers.• A correction procedure was used; trials continued until a response to S+ occurred.• S+, S- locations were varied pseudorandomly

--------------------------------------------------• First set (A) - 2 different olfactory stimuli • All other sets - 6 stimuli (3 from each class)• Stimulus classes (A1-S1 and A2-S2) were established for use in later phases (e.g. equivalence testing). • Following criterion performance (2 consecutive days at ≥ 90%) on a set, Novel Probes were conducted.•Generalized MTS was tested via probe sessions conducted during the first session with novel stimuli.

•Novel Probes: first 6 trials when novel stimuli serve as samples.

• To ensure control of responding by stimulus odor, and not pellet odor, probes were not baited (reinforcers were delivered after response to S+).

•Novel Combinations: later trials within the first session of a set, with novel sample-comparison stimulus combinations.

• Occasional inter-rater reliability sessions were conducted and high levels of observer agreement were found (98% agreement on 128 trials).

References

Iversen, I.H. (1993). Acquisition of matching-to-sample performance in rats using visual stimuli on nose keys. Journal of the Experimental Analysis of Behavior, 59, 471-482.

Iversen, I.H. (1997). Matching-to-sample performance in rats: A case of mistaken identity? Journal of the Experimental Analysis of Behavior, 68, 27-45.

Peňa, T., Pitts, R., & Galizio, M. (2006). Olfactory Identity Matching in the Rat Using Olfactory Stimuli. Journal of the Experimental Analysis of Behavior, 5, 203-221.

  Introduction

• Emergence of generalized identity matching-to-sample (MTS) was evaluated in rats using olfactory stimuli and multiple exemplars in an open-field apparatus. • Generalized identity MTS is often used to study concept learning.• With the exception of Peňa, Pitts, & Galizio (2006), generalized identity MTS has been difficult to demonstrate in rats (Iversen, 1993 & 1997).• Olfactory stimuli may have contributed to the success of Peňa et al. (2006).• The current study replicated Peňa et al. (2006) using the same olfactory discrimination procedure wherein subjects are trained to dig in scented sand to obtain pellet reinforcers.

• A different version of multiple exemplar training was used to train subjects the identity relation.• The open-field arena apparatus, unlike the modified operant chamber used in Peňa et al. (2006), varied spatial locations of comparisons and may facilitate control by the stimuli.

Contact information: lbp0327@uncw.edu

Methods

• Five male, HSD rats were trained to remove perforated lids and dig in cups of scented sand to obtain pellet reinforcers using shaping procedures.• Perforated plastic lids were placed on top of the stimulus cup rim. • Stimuli were mixed using a 10g spice/1000g sand ratio.• Subjects were trained the MTS relation and tested for generalized matching in the open-field arena apparatus.

• 2 circular arrays, numbered clockwise• 94cm diameter, 18 5cm holes, 13cm apart

Conclusions and Future Directions

Evaluating Olfactory Identity Matching-To-Sample (MTS) in Rats Using an Open-field Apparatus

Poerstel, L. B. Bullard, L. A., Rayburn-Reeves, R. M., Weiland, K., Bruce, K. E., & Galizio, M.

University of North Carolina - Wilmington

Figure 1.Percent Correct for individual sessions across stimulus presentations. Panel labels denote stimulus sets, horizontal line indicates criterion, vertical denotes phase change. Fractions are correct responses during Novel Probes (first 6 Novel trials of the first session of a set where novel stimuli serve as samples) over total possible (6). Percentages indicate percent correct for Novel Combinations (trials within first session of a set, after Novel Probes, with novel sample-comparison stimulus combinations).

Sample Stimulus Arrangement - Subject F3

Set 1: A1 Nutmeg A2 DillSet 2: B1 Celery B2 CinnamonC1 Clove C2 GingerD1 Oregano D2 OnionSet 3:E1 Thyme E2 CorianderF1 Mustard F2 SumacG1 Cumin G2 MarjoramSet 4:H1 Garlic H2 RosemaryI1 Sage I2 TurmericJ1 Bay J2 PaprikaSet 5:K1 Sassafras K2 HickoryL1 Worcestershire L2 OrangeM1 Savory M2 FennelSet 6:N1 Carob N2 AllspiceO1 Beet O2 CarawayP1 Lime P2 Tomato

Percent Correct for Consecutive Sessions Across Stimulus Set Presentations

Per

cen

t C

orr

ect

(%)

12

1

2

3

4

5

67

8

9

10

11

13

14

15

16

17

18

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 640.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

90.0

100.0

3/6(58%)

4/6

(92

%)

1/6

(67

%)

2/6(67%)

3/6(92%)

5/6

(92

%)

5/6

(67

%)

4/6(92%)

* *

0 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45 48 51 54 57 60 63 66 69 72 75 78 81 84 87 90 930.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

90.0

100.0

3/6(50%)

3/6 (27%)

4/6 (83%) 4

/6 (

83

%)

4/6(75%)

Consecutive Sessions

Subject G8

Subject G13

Subject H8

Subject F6

Subject F3

Subject

F3 F6 G13 G8

Pe

rce

nt C

orr

ect (%

)

0

10

20

30

40

50

60

70

80

90

100

NovelsLast Two NovelCombinationsLast Two Combinations

23/3

0*

10/1

2*

45/5

4*

18/2

0*

25/3

6* 1

0/1

2*

57/6

3*

18/1

8*

27/4

8

75/9

6*

14/1

8*

18/3

0

8/1

2

38/5

9* 19/2

4*

8/1

2

30/3

6*

*binomial significance = .05

Summary Across Novel Probe and Novel Combination Probe Conditions for Individual Subjects

Figure 2. Average performance for each subject during all Novel Probes compared to the last two Novel Probes, and all Novel Combinations compared to the last two Novel Combinations. Horizontal line indicates chance performance.