Introduction

Justification for replication

Valence is among the principle constructs used to explain animal behavior; we tend towards things we like, away from what we don’t. Remarkably, not much is known about how valence effects processes upstream of decision-making–e.g. memory and perception. In the hopes of characterizing the relationship between valence and perceptual processing, Schechtman et al. 2010 showed differential patterns of generalization in a perceptual learning paradigm, as a function of valence. After a learning protocol where an auditory cue was positively reinforced, subjects were better at discriminating between the original cue from similar tones; subjects performed worse at this task when the tone was negatively reinforced.

My hope is to build upon this core finding–differential generalization as a function of valence–in order to study how these perceptual processes interact with memory. By replicating this study in an online sample, I would be well positioned to iterate through paradigms, eventually converging on a study that will enable me to explore the relationship between valence and memory.

Description of procedures

There are two stages in this experiment which repeat; an acquisition stage and a generalization stage.

Acquisition stage:

In each trial subjects hear one of three auditory tones (300Hz, 500Hz, or 700Hz) which are presented for 200ms, and respond with one of two key presses (e.g. p or q) For the “positive” tone (either 300Hz or 700Hz, randomized across subjects), subjects are rewarded when they press the correct key (e.g. p), and receive no reward otherwise. For the “negative” tone (the complimentary 300Hz or 700Hz tone), subjects are penalized unless they press the correct key (e.g. q)–that is, they receive no penalty only if they press the correct key. Subjects have 2500ms to register a response; if no key press is registered in this time, that trial is marked as ‘incorrect’. Subjects receive feedback based on their performance: the monetary value of their action (e.g. +$0.02, -$0.02, -$0.00, or +$0.00) is displayed at the center of the screen for 1000ms. For a third, “neutral” tone, the tone is presented, but subjects are not required to take any action, and no feedback is given, though the timing of these trials is the same as above. At the end of each acquisition stage, subjects are given feedback about the aggregate bonus accrued in that stage.

Generalization stage:

Subjects are presented with the original three tones, as well as range of similar (300 | 700 ± 5, 20, 60, and 100 Hz) and dissimilar tones (80, 100, 120, 480, 500, 520, 880, 900, or 920Hz). If the tone presented is either the positive or negative tone in the acquisition stage, subjects are instructed to press the key that corresponded to that tone (p or q). Otherwise, they are instructed to press a third key (spacebar). Subjects are asked to respond within 2500ms and are rewarded for correct response within this time, though no feedback is given. If subjects do not respond within the alotted time, they are penalized, and given feedback (-$0.10 RESPOND FASTER).

The acquisition and generalization stages are repeated until subjects have gone through three acquisition-generalization cycles.

Results

Data preparation

In the original study, subjects learned the tone-response contingencies in the initial acquisition stage within <10 trials. Chance performance is 50%, resulting in a total bonus of $0.00. This design incentives subjects to remain engaged in a way that is well suited for an online setting. Additionally, the resulting pattern of behavioral evidence will allow us to identify subjects who were not engaged (e.g. performance around chance). Any subjects who are not performing above 80% accuracy within the first block will be excluded from further analysis.

The remaining data will be aggregated across subjects. The frequency data will be reformatted in terms of the absolute value of the distance between each of the valence_types (positive, negative, and neutral). Then, the p(response) for each type of key presses (‘p’, ‘q’, ‘spacebar’) will be plotted as a function of distance, for frequencies at or below distances of 100Hz (as in Figure 2A in Schechtman et al. 2010)1.

Confirmatory analysis

Referencing the format from the plot above, the primary question this replication hopes to address is “Are the slopes between the positive and negative key responses different?” Using an ANOVA this can be modeled as p(response) ~ distance * valence_type, where we expect the interaction term distance * valence_type to be significant. We also, expect the slope for the negative valence term to be less than the postive valence, signifying “wider generalization”.

Notes

  1. There is an false equivalence in the authors interpretation of the neutral condition analysis. Unlike the ‘p’ and ‘q’ responses during the generalization stage, a ‘spacebar’ response from the subject was not for the purpose of identifying the corresponding tone from the acquisition stage. Instead the spacebar was used for signaling that “This was not the positive or negative tone that I heard in the acquisition phase.” Positive and negative errors in the generalization stage can clearly be interpreted as subjects failing to recognize the stimuli as distinct from the “positive” and “negative” tones in the acquisition stage–this is in line with subjects instructions. Neutral errors, however (when subjects pressed ‘q’ or ‘p’ instead of “spacebar”) should be interpreted as a subject mistaking the tone for a “positive” or “negative” tone, not failing to recognize the difference between the tone presented and it’s acquisition-stage referent. A manipulation that would allow for this equivalence would be to a) have subjects learn to press another button (e.g. ‘g’) during the generalization stage (e.g. a tone-“press to move on” association), then b) have subjects press this key to signal the neutral tone in the generalization stage, and ‘spacebar’ if the tone had not previously been heard.