All methods described here have been approved by the Institutional Animal Care and Use Committee (IACUC) of Providence College.
1. Creating the Testing Apparatus
2. Developing Preferred Food Reward Hierarchy/Preference Testing
3. General Methods
4. Training to Dig in Sand Cups and Habituation to Testing Apparatus
5. Match-to-Sample (MTS) Training
6. Delay Titration in Delayed Match to Sample (DMTS)
7. Decline Use Training
8. Testing: Forced vs. Choice Trials
9. Suggested Generalization Tests
10. Data Analysis
In order to study the metacognitive responding of the subject, the proportion of correct forced trials (baseline memory performance) is compared with the proportion of correct chosen trials, or trials in which there is a decline option present. Positive results are indicated by significantly higher accuracy on chosen trials as compared to forced trials (Figure 2A). These results indicate that rats may be monitoring their memory states and declining the task when their memories are weak, leading to an increase in accuracy when a decline option is present on chosen trials.
If performance is not significantly more accurate on chosen trials as compared to forced trials, results are null. This hypothetical lack of evidence for metamemory in rats (Figure 2B) is indicated by failure to use the decline-test option when it would have been adaptive to do so: on trials in which the sample was forgotten.
If generalization tests are run, metacognitive performance would be indicated if subjects decline no-sample trials significantly more normal sample trials and decline double sample trials significantly more than normal sample trials. Decline use should show an inverse relationship with memory accuracy as indicated on accuracy on forced trials. If accuracy on forced tests does not vary with trial condition, change parameters (e.g. increase RI) as it is impossible to determine if subjects are or are not behaving metacognitively. On mixed delays tests, accuracy on chosen tests should be significantly higher than accuracy on forced tests and subjects should be more likely to decline tests with longer RIs and least likely to decline tests with shorter RIs. See results paper for more details on generalization tests and respective interpretations19.
Figure 1. Photograph of experimental apparatus and process. A) Photograph of apparatus adapted from19 with permission. B) Experimental process. The first step of habituation, teaching rats to dig in sand-filled cups, takes place over two nights. Next, the rats are habituated to the experimental apparatus and are trained to dig in sand-filled cups there. Subjects are then given the choice of two rewards, represented as a green triangle and red crescent (whole piece of cereal vs. a quarter piece of cereal). After rats show a significant preference for one reward, they transition to MTS training, in which cups are filled with scented sand, represented by images of cinnamon, paprika, thyme, and coffee. If the success rate is below 50% for two sessions, the subject continues training. If the success rate of the rats is at 50% or above, the subject progresses to delay titration. During delay titration, rats continue with MTS training, but a delay between the sample and test is introduced (starting with 0 s). If rats' memory accuracy is above 70%, then the RI is increased. If accuracy falls below 40%, the RI is decreased, and MTS training continues. This loop continues until rats' accuracy falls between 40% and 70% for two consecutive sessions. At this point, rats progress to the experimental test which consists of randomly intermixed forced and choice trials. Please click here to view a larger version of this figure.
Figure 2. Positive results indicating metacognitive responding and hypothetical null results indicating lack of metacognitive responding. A) Positive results adapted from 19 with permission. The average proportion correct of forced and chosen trials was derived from the performance of 9 rats on 120 trials each. *=p<.05 on paired two-tailed t-test. A significantly higher proportion of trials answered correctly on chosen trials as compared to forced trials indicates the appropriate use of the decline-test response. B) An equivalent proportion of trials answered correctly on forced and chosen trials indicates lack of declining tests on the basis of memory strength. Chance, 0.25, is indicated by the dotted line. Error bars represent standard error of the means. Please click here to view a larger version of this figure.
Froot loops | Kellogg's | B00I8QZ4HM | Sweetened cereal |
Sociability Chamber | Noldus Technologies | 46503 / 46553 | |
Black Contact Paper | Con-Tact | B000KKMO90 | |
Cardboard | |||
Ceramic small animal dishes | Norpro | B00061N0QO | 7 cm. in diameter and 3.8 cm tall |
Play sand | ACTIVA | B004BNBXJ4 | White Sand |
Duct Tape | 3M | B001HT720O | Black duct tape |
Cinnamon | Simply Organic | FNTR07824 | Amazon |
Coffee | Folgers | B016KZTPJU | Amazon |
Paprika | Simply Organic | B06XB9QGVB | Amazon |
Thyme | Simply Organic | 579193 | Amazon |
Colored Sand | Sandtastik Products | B000Q4O9UW | Orange sand |
70% isopropyl alcohol | Swan | B00HKDI6WO | Amazon |
Dust buster (vacuum) | Black + Decker | B01DAI5BZ2 | Cordless vacuum |
Metal tracks | Home Depot | EC751BA | Used for door in chamber |
Spatula | Chef Craft | B00B0M5LQK | Bent at a right angle to lower sample cup into testing apparatus |
Metamemory involves the cognitive ability to assess the strength of one's memories. To explore the possibility of metamemory in non-human animals, numerous behavioral tasks have been created, many of which utilize an option to decline memory tests. To assess metamemory in rats, we utilized this decline-test option paradigm by adapting previous visual delayed-match-to-sample tests (DMTS)1,2 developed for primate species to an odor-based test suitable for rodents. First, rats are given a sample to remember by digging in a cup of scented sand. After a delay, the rat is presented with four distinctly scented cups, one of which contains the identical scent experienced during the sample; if this matching cup is selected, then the rat obtains a preferred, larger reward. Selection of any of the other three non-matching sand-filled scented cups results in no reward. Retention intervals are individually titrated such that subjects perform between 40 and 70% correct, therefore ensuring rats sometimes remember and sometimes forget the sample. Here, the operational definition of metamemory is the ability to distinguish between the presence and absence of memory through behavioral responding. Towards this end, on two-thirds of trials, a decline option is presented in addition to the four choice cups (choice trials). If the decline-test option- an unscented colored sand cup, is selected, the subject receives a smaller less-preferred reward and avoids the memory test. On the remaining third of trials, the decline-test option is not available (forced trials), causing subjects to guess the correct cup when the sample is forgotten. On choice tests, subjects that know when they remember should select the decline option when memory is weak rather than take the test and choose incorrectly. Therefore, significantly higher performance on chosen tests as compared to forced memory tests is indicative of the adaptive use of the decline-test response and metacognitive responding.
Metamemory involves the cognitive ability to assess the strength of one's memories. To explore the possibility of metamemory in non-human animals, numerous behavioral tasks have been created, many of which utilize an option to decline memory tests. To assess metamemory in rats, we utilized this decline-test option paradigm by adapting previous visual delayed-match-to-sample tests (DMTS)1,2 developed for primate species to an odor-based test suitable for rodents. First, rats are given a sample to remember by digging in a cup of scented sand. After a delay, the rat is presented with four distinctly scented cups, one of which contains the identical scent experienced during the sample; if this matching cup is selected, then the rat obtains a preferred, larger reward. Selection of any of the other three non-matching sand-filled scented cups results in no reward. Retention intervals are individually titrated such that subjects perform between 40 and 70% correct, therefore ensuring rats sometimes remember and sometimes forget the sample. Here, the operational definition of metamemory is the ability to distinguish between the presence and absence of memory through behavioral responding. Towards this end, on two-thirds of trials, a decline option is presented in addition to the four choice cups (choice trials). If the decline-test option- an unscented colored sand cup, is selected, the subject receives a smaller less-preferred reward and avoids the memory test. On the remaining third of trials, the decline-test option is not available (forced trials), causing subjects to guess the correct cup when the sample is forgotten. On choice tests, subjects that know when they remember should select the decline option when memory is weak rather than take the test and choose incorrectly. Therefore, significantly higher performance on chosen tests as compared to forced memory tests is indicative of the adaptive use of the decline-test response and metacognitive responding.
Metamemory involves the cognitive ability to assess the strength of one's memories. To explore the possibility of metamemory in non-human animals, numerous behavioral tasks have been created, many of which utilize an option to decline memory tests. To assess metamemory in rats, we utilized this decline-test option paradigm by adapting previous visual delayed-match-to-sample tests (DMTS)1,2 developed for primate species to an odor-based test suitable for rodents. First, rats are given a sample to remember by digging in a cup of scented sand. After a delay, the rat is presented with four distinctly scented cups, one of which contains the identical scent experienced during the sample; if this matching cup is selected, then the rat obtains a preferred, larger reward. Selection of any of the other three non-matching sand-filled scented cups results in no reward. Retention intervals are individually titrated such that subjects perform between 40 and 70% correct, therefore ensuring rats sometimes remember and sometimes forget the sample. Here, the operational definition of metamemory is the ability to distinguish between the presence and absence of memory through behavioral responding. Towards this end, on two-thirds of trials, a decline option is presented in addition to the four choice cups (choice trials). If the decline-test option- an unscented colored sand cup, is selected, the subject receives a smaller less-preferred reward and avoids the memory test. On the remaining third of trials, the decline-test option is not available (forced trials), causing subjects to guess the correct cup when the sample is forgotten. On choice tests, subjects that know when they remember should select the decline option when memory is weak rather than take the test and choose incorrectly. Therefore, significantly higher performance on chosen tests as compared to forced memory tests is indicative of the adaptive use of the decline-test response and metacognitive responding.