Paradigm and Hypotheses

This document plots the results of a 30 min version of Auditory Ensembles. In this task, subjects performed an auditory memory task in which they remembered a single pure tone (300 ms duration) over a delay with distractors. Subjects remembered the first tone of the presentation, which was then followed by 4 pure tone distractors after a 2000 ms ISI. Each of these distractor tones had an ISI of 300 ms. The tones were either +/-1, 3, or 5 semitones from the remembered tone and were chosen such that their average pitch was either equal to, higher than, or lower than the to-be-remembered tone with equal probability. Following the final distractor tone, there was a 2 sec delay. Participants then reported which of two test tones (target and +/- 2 semitone away foil) they heard at the beginning of the trial (i.e. 2IFC) using the v (first) and n (second) keys. There was an ITI of 3000 ms. We designed the task to see if ensemble information biases individual auditory memory representations. We hypothesized that subjects would be more likely to pick foils when they were in the same direction from the remembered tone as the ensemble (i.e. less accurate in task), and less likely to pick foils when they were in the opposite direction from the remembered tone as the ensemble (i.e. more accurate).

This version of the task is nearly identical to the one run as “Aud_Ens_long_delay_3_3_fixed”. The only changes were to (1) emphasize that headphones must be used to decrease subject rejection rate and (2) include questions to ask about years of musical experience and perfect pitch.

Note: All error bars represent standard error of the mean. Subjects who had a d’ of less than .5 after collapsing across all conditions were excluded.

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Subjects’ (N = 90) overall performance, before exclusion

Reasons for exclusion

reason number
Excluded for d’ alone 21
Excluded for headphone check alone 12
Excluded for both 6

Subjects’ (N = 51) performance on task, after exclusion

Target discrimination d’

In the same ensemble condition, the distractor tones had the same average pitch as the target tone. In the “opposite direction of foil” condition, the distractor tones had an average pitch higher or lower than the target tone and the foil was in the opposite direction of the ensemble. For example, if the distractor tones had a higher pitch than the target tone, then the foil would in this case be of lower pitch than the target tone. In the “same direction as foil” condition, the distractor tones had an average pitch higher or lower than the target tone and the foil was in the same direction as the ensemble. For example, if the distractor tones had a higher pitch than the target tone, then the foil would in this case also be of higher pitch than the target tone. If subjects are biased by the average pitch of the distractor tones, then we would expect that they are worse in the “same direction” condition than in the “opposite direction” condition. This is because the foil in the “same direction” condition will be a more effective lure in this case given that it is in the direction of the memory bias; and the foil in the “opposite direciton” condition will be a less effective lure given that it’s further away from the biased memory. If there is no bias, then we would expect subjects to perform at the same level in each of these conditions.

Target discrimination RT

Manipulation Checks

d’ with target first vs. second

Frequency of choosing first vs. second interval

d’ with foil higher vs. lower

d’ by average RT

## `geom_smooth()` using formula 'y ~ x'

Statistics

d’ ANOVA

Effect DFn DFd SSn SSd F p p<.05 ges partial_eta_squared
(Intercept) 1 50 242.462 82.892 146.252 0.000 * 0.713 0.745
taskCondition 2 100 1.995 14.774 6.752 0.002 * 0.020 0.119

d’ t-tests

comparison t_val p_val
same ensemble vs. opposite direction -1.783105 0.0806401
same ensemble vs. same direction 2.047540 0.0458767
same direction vs. opposite direction -3.549249 0.0008516


RT ANOVA

Effect DFn DFd SSn SSd F p p<.05 ges partial_eta_squared
(Intercept) 1 50 1.990884e+08 41218038 241.506 0.000 * 0.802 0.828
taskCondition 2 100 4.058079e+03 7975733 0.025 0.975 0.000 0.001

RT t-tests

comparison t_val p_val
same ensemble vs. opposite direction -0.0711611 0.9434146
same ensemble vs. same direction 0.0415277 0.9669598
same direction vs. opposite direction -0.1052201 0.9164120