Wills et al. (2009), Exp. 1A - clarifications ============================================= During the compilation of this DAU in 2016, I discovered a number of places in Wills et al. (2009, JCP) where the description of the Methods and Results of Experiment 1A was poor. This document fills in the gaps and corrects the errors. Method ------ 1. The observing response is on a FT 10s schedule. 2. The schedule on the response keys is "tand FT 2s VI 0.5s". VI 0.5s is implemented as a random selection, on each trial, of 0 seconds and 1 second. 3. Phase 1 training started with a session length of 80 trials. Birds were subsequently moved to a 64-trial session length for phase 1 later on. 4. In some Phase 1 sessions, a forced-choice procedure was used on most or all trials. This is where the pigeon cannot proceed to the next trial until it pecks the correct key. Forced-choice trials are indicated in the raw data file in column 'fc' by the presence of an 'F'. 5. References in Wills et al. (2009) to number of sessions completed in phase 1 do not count 80-trial sessions, forced-choice sessions, or some other sessions. For archival purposes, the session numbering as used in the original paper is in column 'lsess'. The column 'sess' provides a simple incremental count of sessions started. Column 'sess' is used in the current analyses. 5. In rare cases, there was up to three weeks between one session and the next. Technical / experimenter errors ------------------------------- 6. There was a technical error that led to two birds being passed to phase 2 without meeting the stated criterion (details in Results below). The technical error can be reproduced by using column 'snum' in the data file. 7. Three birds (At, Io, Ly) had an additional test session. These are included the raw data file. 8. In some sessions, one or both of the food delivery hoppers malfunctioned. These sessions are included in the raw data file. 9. For one session (As, 2006-07-03), the data did not record. This session is indicated in the raw data file. Results ------- Phase 1 - Although every bird had an accuracy of at least 75% on their final phase 1 session, two birds (At, Ly) did not pass the criterion of being at least 75% accurate on both levels of at least three dimensions (they both passed it on two dimensions). This was due to a technical error. One can reproduce this error by using column 'snum' in your analysis. For all other purposes, use column 'stim'. Phase 2 - The criterion is 87.5%. All birds reach the criterion, taking between 1 and 9 sessions to do so. Test sessions - The excess test sessions (see Experimenter errors, above) were removed prior to analysis (session numbers - At: 76, Io: 63, Ly: 67). Table 1 of Wills et al. (2009) contains some arithmetic errors, a corrected version is shown below. In all but one case, the identified strategy is unchanged. For bird Pn, the reported Overall Similarity strategy ties with a Unidimensional (Donut) strategy. This change does not affect the conclusions reported in the paper. In particular, the birds in Experiment 1A and the humans in Experiment 1B do not differ significantly in the proportion of OS sorters observed. The trend remains for OS to be more prevalent in humans than in pigeons, contrary to predictions of Differentiation Theory. Table 1 (replacement): Percentage of one-away test trials. subj bar chk loz don os win As 39 61 58 58 chk At 39 72 50 61 chk Ba 54 51 46 51 bar Io 65 46 58 71 os Le 44 47 72 64 don Ly 53 64 50 67 os Pn 49 51 62 62 os/don Sf 62 49 54 65 os Andy Wills 2016-02-22