Implicitly learning when to be ready - From instances to categories

Wouter Kruijne · Riccardo M. Galli · Sander A. Los
role of long-term memory in guiding temporal preparation in speeded reaction time tasks.
In experiments with variable foreperiods between a warning stimulus (S1) and a target stimulus (S2), preparation is affected by foreperiod distributions experienced in the past, long after the distribution has changed
associative nature of memory-guided preparation
When distinct S1s predict different foreperiods, they can trigger differential preparation accordingly
memory-guided preparation allows for another key feature of learning: the ability to generalize across acquired associations and apply them to novel situations
Images of either category were paired with different distributions with predominantly shorter versus predominantly longer foreperiods.
differential preparation to never-before seen images of either category, without being aware of the predictive nature of these categories
continued doing so in a subsequent Transfer phase, after they had been informed that these contingencies no longer held
rolling regression analysis revealed at a fine timescale how category-guided preparation gradually developed throughout the task
explicit information about these contingencies only briefly disrupted memory-guided preparation

Preparation across phases

the RT-FP curve, separately for the different S1 types during the Acquisition and Transfer phase
this curve is flatter for trials paired with S1E types than S1A types in both phases, indicating that the categories yielded differential preparation
significant FP × Phase interaction
suggesting that there was a steeper RTFP slope during Acquisition than during Transfer
evidence for a two-way S1 type × FP interaction
but not for a three way S1 type × Phase × FP interaction
different S1 types led to differential preparation in both phases
biased distributions in the Acquisition phase gave rise to long-lasting effects on preparation, persisting after the bias was removed

participants might have gotten somewhat fatigued throughout each block, but that block breaks allowed them to largely recover to baseline
the longer interruption between the Phases led to a more pronounced speeding up for the remaining two blocks
overall temporal preparation remained largely consistent throughout the experiment
the results with a shorter window of 40 trials highlight that the ‘dip’ in the S1 type × FP time course at the start of the Transfer phase was very shortlived
The brevity of this effect could therefore explain why our earlier work, using block-wise analyses, consistently led us to conclude that this transition between phases had no noticeable effect on differential preparation

Our findings raise the possibility that participants in that study might have demonstrated similar memoryguided preparation even if they would have been unaware of the image-FP pairings
complex interplay between implicit associative guidance and guidance by explicit awareness
Nevertheless, differential preparation was robust once acquired, persisting well into the Transfer phase despite the change in underlying FP distributions
longer Transfer phases, we similarly observed that the S1 type × FP interaction barely attenuated across Transfer blocks
The gradual acquisition of differential preparation and its longevity throughout the Transfer phase illustrate how temporal preparation is affected by long-term memory and sluggishly adapts to changing environmental statistics
Many probability-driven models characterize preparation as guided by static representations of the current FP distribution (Janssen & Shadlen, 2005; Grabenhorst et al., 2019; Trillenberg et al., 2000; Vangkilde et al., 2013), foregoing the role of memory and learning
Transfer effects like those in the present study illustrate the need for a flexible basis for preparation, subject to learning and updating