Latent inhibition and eye tracking.

In a previous post I promised these data.  Here, participants undergo a latent-inhibition treatment, or not, and their gaze is monitored during the experimental task. This experiment follows up on a pilot study conducted last year.

The method is the video game task described elsewhere where responses are first attached to spaceship USs, and then those spaceships are signaled by sensor CSs.  As participants associate these events, responding emerges to the CS before the US appears.

The design was very simple. 

•Group Latent Inhibition  6 R- |10 R+ | 10 R-

•Group Control  6 — |10 R+ | 10 R-

Group Latent inhibition received 6 presentations of a red sensor CS, while Group Control simply sat and observed the game with no events occurring.  Then, both groups received 10 trials where the red CS was paired with a spaceship that emerged from within the top left quadrant of the screen.  Following conditioning, both groups received 10 extinction trials.

Pre-Exposure

Group Latent Inhibition: First pre-exposure trial

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The screen above is a heat map of the first pre-exposure trial.  What it shows is that the LI group looked at the sensor (circular area) more than the rest of the screen. Compare the pattern to that of the Controls below.

Group Control: First pre-exposure trial (No stimulus presented)

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Here, the group distributes its gaze more uniformly across the screen, with some focus on the station (not shown in the background used for the heat map). 

By the last pre-exposure trial, the pattern had changed.

Group Latent Inhibition: Last pre-exposure trial

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Although the sensor was looked at repeatedly more often than the rest of the screen, other hotspots emerged, thus, looking at the sensor had declined.   The control group, on the other hand (see below), was showing essentially the same pattern as on the first trial.

Group Control: Last pre-exposure trial

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There is an interesting pattern to point out here.  Look closely at the last two maps above and you might notice that there appear to be more points on the left of the screen than on the right.  This trend was reliable. Participants, for whatever reason, preferred to look at the left of the screen over the right side.   The attending researcher was seated to the participant’s right, but whether that was a contributing factor is unknown.

The next task was to quantify the data presented above, the results of which are presented below.

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The figure shows the seconds spent looking at the CS for each group, for each second of each trial.  Notice that the control group (solid circles) does not look in the area of the CS.  The latent-inhibition group begins looking at the CS, but that orienting habituates.  Notice also the pattern closely matches what one would expect with the operation of two habituation mechanisms (short term and long term).  Within the CS, orienting decreases and then recovers somewhat between presentations.  Overall, between presentations, orienting decreases.  

When not looking at the CS, they are looking at other parts of the screen.  As shown in the earlier heatmaps, the screen is divided into five sections, 1: the circular section around the CS, 2: the upper left, 3: upper right, 4: lower left, and 5: lower right.  The upper left was referred to as the “US Zone” because that was where the US always appeared; somewhere from within the upper left quadrant.  The figure below shows participants’ gaze position on the screen, collapsed across groups because they did not differ in how they distributed their gaze across the rest of the screen in this phase.

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On some seconds of some trials there was a significant preference for looking in the US Zone, at least over looking at the bottom right.  These points were likely artifacts of preferring to look to the left of the screen.  Within both the top and bottom sections, the circles (left) are higher than the corresponding triangles (right).  (Orange > blue, red > yellow)

Conditioning

The next figure shows the behavioral keypress response data for the two groups during each second of each trial of conditioning.  All figures in this section show the first 5 seconds of the CS.  After that, the US appears and generates considerable responding.  With the eyes, once the US appears their gaze is focused on the US.

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Robust group differences emerged on trial 4 and persisted across the phase.  On trial 9 there were no reliable differences, but there were again on trial 10.  Thus, after 9 trials of conditioning the response levels between the two groups had not  yet converged: Robust evidence of Latent Inhibition was obtained.  Moreover, it is worth noting that such evidence was obtained without the use of a masking task.

Latent Inhibition: First conditioning trial

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The first conditioning trial looked more or less like the last pre-exposure trial, with looks at the sensor and other looks distributed across the screen.  However, the Control group was receiving the sensor for the first time…

Control Group: First conditioning trial

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…and they directed their attention, as expected, predominately at the sensor.  By the last trial of conditioning, interesting patterns had emerged.

The top image below shows the heatmap for the Latent inhibition group on the last conditioning trial, while the next one following below shows that for the control group.  What each shows is that gaze was directed toward the sensor, and also to the upper left zone of the screen, the US Zone.  Over trials, participants came to expect the US and direct their attention to where it would appear.

Latent Inhibition: Last conditioning trial

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Control: Last conditioning trial

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Looks at the sensor are summarized below.  The control group clearly looked at the sensor more than did the latent inhibition group.  In the Latent inhibition group, looking at the sensor during the first second of each trial increased after the first trial.  But, overall (see trials 5, 8, and 10) attention to the CS in the latent inhibition did not quite match the level observed in the control group.

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When not looking at the CS, participants came to direct their gaze to the area of the screen where the US would appear, as shown by the red lines in the figure below.

imageThere was some trend for the Control group to show this CS-directed goal-tracking response more strongly (see trials 4, 5, 7, & 9: But see trial 8).   These responses are complicated somewhat by the unconditioned tendency in both groups to prefer looking in that area, yet the preference during the CS was considerably more pronounced.

Extinction

The figure below shows the behavioral data for extinction.  At this point, the groups did not differ.  Thus, they converged behaviorally after 10 conditioning trials.  No US was present, so I am showing behavior elicited by the CS over the entire 20-s of the CS.  Both groups showed a timed response.  Their responding increased to the point where the US was expected (indicated by the yellow arrows) and then began to decrease.  Thus, there was a within-trial decrease in responding, likely due to a generalization decrement, and a between-trial decrease likely due to extinction processes.

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The eye data at the beginning of extinction did not differ from that at the end of conditioning.  However, the pattern had changed by the end of extinction.

Both the Latent Inhibition Group (below) and the Control group (2nd map below) directed some attention to the CS, but their goal tracking response had extinguished.  When not looking at the CS, they distributed their gaze more evenly across the screen.

 Latent Inhibition: Last extinction trialimage

Control: Last extinction trial

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The figure below summarizes the looks directed at the sensor CS.  It collapses across groups as there were no meaningful differences between groups, and it averages across every two trials to improve clarity.

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There was no change in the first second over trials.  The first second still commanded at least a brief 1/4 second glance.  After that, looks to the CS decreased up till the time when the US was expected (indicated by the arrow).  At that point, looking at the CS increased on trials 1-6, during the time the US was expected, but absent.  Once the US did not occur, on trials 7 and 8 there was little change in looking at the CS during that time, and on trials 9 and 10 looking at the CS continued to decrease.  

Extinction produced a small increase in attention to the CS that itself declined as extinction progressed.

The final figure below shows the participants’ gaze over the rest of the screen.  At the start of extinction they looked predominately at the zone where the  US would appear, and that declined over trials as looks at other areas increased.  One group may show more responding than another on some second of some trial in some zone, but overall there are no meaningful group differences here.

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Now that you have got this far, the animated version is below.

Byron Nelson presenting at the 2011 congress of the Spanish Society of Comparative Cognition, Sept 21, 2011.

Caveat: These blog entries are generated quickly, and though I do hope to communicate something, their main purpose is to serve as a repository for what I was thinking about particular sets of data that I can refer to when I get around to writing them up. So what you read here, as far as writing goes, is essentially in first and rough draft form. So, while I appreciate feedback, pointing out my grammar errors & whatnot isn’t really useful at this stage.

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2 Responses to Latent inhibition and eye tracking.

  1. Pingback: Latent inhibition is not context specific & eye tracker demands? | Byron's blog.

  2. Pingback: A pre-exposure effect that is enhanced with a change in context- | Byron's blog.

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