> For the complete documentation index, see [llms.txt](https://manymanys.gitbook.io/mm1-lab-manual/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://manymanys.gitbook.io/mm1-lab-manual/glossary/key-terms.md). # Key terms #### Choice The selection by either physical contact with or close proximity (≤ 1 centimer) to S+ (rewarded stimulus) or S− (unrewarded stimulus). A failure to select either stimulus within the maximum trial length is designated as NA (no choice). For NAs, the reason for not selecting either stimulus should be recorded (e.g., does not engage/respond, engages but fails to choose, “fuss out”, etc.). #### Acquisition phase The initial testing phase in which subjects are trained to discriminate between two stimuli, one of which is associated with a reward (S+), while the other is not (S−). The acquisition phase continues until the subject either achieves the learning criterion or reaches the maximum phase length. #### Inter-trial interval (ITI) The temporal gap between the end of one trial and the beginning of the next trial. The ITI begins immediately after the outcome of the previous trial (reward delivery, no reward, or no choice) and ends when the stimuli for the next trial are presented. The duration of the ITI might vary across species or sites (due to differences in reward consumption time, motivational states, handling requirements, etc.), but it must be kept consistent and reported to the MM1 Leadership Team. #### Latency to choice The duration of time between the presentation of the two stimuli at the beginning of a trial and the moment the subject makes physical contact with one of the stimuli (i.e., completes a choice response). Response latency is measured in milliseconds and reflects the speed of decision-making or response execution. Latency is recorded only for trials in which an active choice is made (S+ or S−); trials with no choice (NA) may be assigned the maximum trial length value or coded separately. #### Latency to reward The duration of time between the moment the subject makes physical contact with the rewarded stimulus (S+) and the moment the reward is delivered or becomes accessible to the subject. Latency to reward is measured in milliseconds and reflects the delay in reinforcement following a correct choice. This temporal parameter is determined by the reward delivery method and apparatus used at each testing site (e.g., manual placement of food by experimenter, automated dispenser, immediate access to pre-placed reward). #### Learning criterion The predetermined performance threshold that a subject must achieve to be considered to have successfully learned the task contingency. It is operationally defined as the correct selection of the rewarded stimulus (S+) in at least 80% of trials within the maximum allotted phase length (see Table in Experiment Overview section). This criterion must be met during both the acquisition phase (to advance to reversal) and the reversal phase (to complete a reversal). If the subject reaches the same learning criterion for selecting S−, this is evidence of a preference bias and the subject should be removed from the analysis and not tested further. #### Maximum trial length The maximum duration of time (in seconds) allowed for a subject to make a choice response on a single trial, measured from the moment stimuli are presented until either (i) the subject makes contact with—or moves into very close proximity to (≤ 1 centimer)—one of the stimuli, or (ii) the trial is terminated due to exceeding the time limit. If no response occurs—or the subject engages but fails to choose (e.g., “fuss out”)—within the maximum trial length, the trial is scored as “no choice” (NA) and a new trial begins following the inter-trial interval. The maximum trial length is determined by the lab/team/site, but must remain consistent within each lab/team/site and be reported to the MM1 Leadership Team. #### Maximum phase length The maximum number of trials a subject is allowed to attempt within a single phase (acquisition or reversal) before testing is terminated for that phase. This parameter prevents indefinite testing of subjects who may not be capable of learning the task and limits the time and resource burden on testing sites and subjects. The maximum phase length is kept constant within species and is specified based on species-specific constraints (e.g., attention span, motivation, session length, welfare considerations). If a subject reaches the maximum phase length without achieving the learning criterion, they are considered a “non-learner” for that phase, though their data may still be included in analyses examining trials-to-criterion or learning curves. #### Minimum phase length The minimum number of trials a subject must complete within a given phase (acquisition or reversal) before being considered to have had adequate opportunity to learn the task contingency. It is set at an absolute minimum of 11 trials, though testing sites should aim to provide as many trials as feasible to maximize the likelihood that subjects will achieve the learning criterion. The trials must be run within a single session (i.e., without interruption). However, testing must not result in overtraining (continuing trials beyond when the subject has reached the learning criterion), as this can affect performance in the reversal phase. The minimum phase length ensures that subjects receive sufficient exposure to the reward contingencies, even if they do not ultimately reach criterion. Subjects who complete fewer than the minimum phase length should not be included in analyses for that phase. #### Perseverative errors (reversal) Incorrect choices during the reversal phase in which the subject continues to select the previously rewarded stimulus (old S+, now S-) despite it no longer providing reward. Perseverative errors reflect the failure to inhibit a previously learned and reinforced response pattern, indicating difficulty with behavioral inhibition and response flexibility. Frequently measured as rates (i.e., proportion of reversal trials in which old S+ was selected) and runs (i.e., number of consecutive perseverative errors immediately following reversal before first correct choice). #### Regressive errors (reversal) Incorrect choices during the reversal phase in which the subject returns to selecting the previously rewarded stimulus (old S+, now S-) after having already demonstrated learning of the new contingency by making correct choices of the new S+. Regressive errors reflect instability in the newly learned association, difficulties with memory consolidation, or susceptibility to interference from competing memory traces. Similar to perseverative errors, regressive errors are frequently measured via rates (i.e., proportion of post-switch trials in which old S+ was selected). Other measures include number of regressions (i.e., count of discrete episodes of reverting to old S+ after making correct choices) and regression depth (i.e., number of consecutive incorrect choices during a regression episode). #### Reversal cost A quantitative measure of the additional cognitive demand associated with reversal learning compared to initial acquisition learning. Reversal cost is commonly calculated as a proportional measure: the number of trials required to reach criterion during the reversal phase divided by the number of trials required during the initial acquisition phase (TTC\_reversal / TTC\_acquisition). #### Reversal count The total number of reversal phases (including initial reversal and interreversal phases) that a subject successfully completes by reaching the learning criterion. Reversal count begins at zero following acquisition and increments by one each time the subject achieves criterion in a subsequent reversal phase. For example, a subject who completes acquisition and then reaches criterion in one reversal has a reversal count of 1; a subject who completes acquisition and reaches criterion in three consecutive reversals has a reversal count of 3. All subjects must complete a minimum of one reversal (reversal count = 1) to be included in reversal learning analyses. Subjects who reach criterion in acquisition but fail to reach criterion in the first reversal phase (within the maximum phase length) have a reversal count of 0 and contribute data only to acquisition analyses. Both attempted and successful reversal counts should be documented at each testing site. #### Reversal learning The process of learning new reward contingencies after previously learned associations are reversed. In this task, reversal learning occurs when the stimulus that was previously rewarded (S+) becomes unrewarded (S−), and the stimulus that was previously unrewarded (S−) becomes rewarded (S+). Reversal learning requires both the inhibition of the previously learned response and the acquisition of a new response pattern. Performance during reversal (e.g., trials to criterion, error patterns) provides a measure of behavioral flexibility—the ability to adaptively update behavior when environmental contingencies change. #### Reversal phase The testing phase that immediately follows successful acquisition, in which the reward contingencies are reversed—the previously rewarded stimulus (S+) becomes unrewarded (S−), and the previously unrewarded stimulus (S−) becomes rewarded (S+). Subjects must detect this contingency change through trial-and-error learning (experiencing reward or no reward outcomes) and update their behavior accordingly. The reversal phase continues until the subject either achieves the learning criterion or reaches the maximum phase length. #### Reward A species-appropriate positive reinforcer delivered immediately following a correct choice (selection of S+) that serves to reinforce the subject’s behavior and motivate continued task engagement. The reward type, quantity, and delivery method must be tailored to each species’ preferences, motivational state, and welfare requirements. For non-human animals, rewards typically consist of preferred food items (e.g., fruit, nuts, fish, seeds, pellets, dead/immobilized insects) appropriate to the species’ natural diet and nutritional needs. The reward should be sufficiently motivating to sustain engagement across multiple trials but not so large as to cause rapid satiation. For human participants, rewards consist of social reinforcement (e.g., verbal praise such as “Well done!”) or other non-food positive feedback (e.g., visual feedback on screen, points, tokens). Food rewards are not provided to human participants. Reward specifications (type, amount/intensity, delivery method) must be consistent within subjects, species, and phases, documented, and reported to the MM1 Leadership Team. #### S+ (rewarded stimulus) The stimulus (location, shape, or color) that, when selected, results in reward delivery. The identity of S+ remains constant throughout a given phase (acquisition or reversal) but varies between phases and individuals. During acquisition, S+ is the initially designated rewarded stimulus; during reversal, S+ is the stimulus that becomes rewarded after the contingency change (i.e., the stimulus that was S− during acquisition). #### S- (unrewarded stimulus) The stimulus (location, shape, or color) that, when selected, results in no reward delivery. The identity of S− remains constant throughout a given phase (acquisition or reversal) but varies between phases and individuals. During acquisition, S− is the initially designated unrewarded stimulus; during reversal, S− is the stimulus that becomes unrewarded after the contingency change (i.e., the stimulus that was S+ during acquisition). #### Serial reversal learning \[also Interreversal learning] The repeated alternation of reward contingencies across multiple reversal phases (e.g., reversal 1, reversal 2, reversal 3). In serial reversal paradigms, subjects undergo acquisition followed by multiple consecutive reversals in which S+ and S− switch repeatedly. Some species show “learning to learn” effects in which subsequent reversals are learned more quickly than the first reversal, potentially indicating meta-learning about the task structure. Serial reversals may be conducted in this study depending on species-specific capabilities, time constraints, and subject motivation. #### Trial A single discrete unit of the task consisting of: (i) presentation of two stimuli in two locations, (ii) an opportunity for the subject to make a choice response within the maximum trial length, and (iii) delivery of the outcome (reward for S+, no reward for S− or NA), followed by the inter-trial interval. Each trial is independently coded for the subject’s choice (S+, S−, or NA) and contributes to the calculation of learning criterion, performance measures, and learning curves. The total number of trials a subject completes varies depending on how quickly they reach criterion and whether they complete multiple reversal phases. #### Trials to criterion (TTC) The number of trials required for a subject to achieve the learning criterion within a given phase (acquisition or reversal). TTC is the primary dependent measure of learning speed: lower TTC values indicate faster learning, while higher TTC values indicate slower learning. TTC can be compared across phases (acquisition vs. reversal), conditions (location vs. shape vs. color cue), and taxa to assess differences in learning efficiency and behavioral flexibility. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. 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