Demonstration of cue recruitment: change in visual appearance by means of Pavlovian conditioning

Abstract

Until half a century ago, associative learning played a fundamental role in theories of perceptual appearance [Berkeley, G. (1709) An Essay Towards a New Theory of Vision (Dublin), 1st Ed.]. But starting in 1955 [Gibson, J. J. & Gibson, E. J. (1955) Psychol. Rev. 62, 32-41], most studies of perceptual learning have not been concerned with association or appearance but rather with improvements in discrimination ability. Here we describe a "cue recruitment" experiment, which is a straightforward adaptation of Pavlov's classical conditioning experiment, that we used to measure changes in visual appearance caused by exposure to novel pairings of signals in visual stimuli. Trainees viewed movies of a rotating wire-frame (Necker) cube. This stimulus is perceptually bistable. On training trials, depth cues (stereo and occlusion) were added to force the perceived direction of rotation. Critically, an additional signal was also added, contingent on rotation direction. Stimuli on test trials contained the new signal but not the depth cues. Over 45 min, two of the three new signals that we tested acquired the ability to bias perceived rotation direction on their own. Results were consistent across the eight trainees in each experiment, and the new cue's effectiveness was long lasting. Whereas most adaptation aftereffects on appearance are opposite in direction to the training stimuli, these effects were positive. An individual new signal can be recruited by the visual system as a cue for the construction of visual appearance. Cue recruitment experiments may prove useful for reexamining of the role of experience in perception.

Fig. 1.

Experimental paradigm to study cue recruitment. Before training, an ambiguous stimulus was equipotential, and a new signal had no effect. During training, stereo and occlusion cues specified the direction of rotation on each trial, and two values of the new signal (-) and (+) were presented in correlation with the two directions of rotation. After training, the new signal disambiguated the rotation [as shown for the (+) signal; the symmetric case for the (-) signal is not shown]. LH, left-handed perceived rotation; RH, right-handed perceived rotation. Typical probabilities for each of these perceptual outcomes are shown in the boxes.

Fig. 2.

Time course of learning in three experiments. The experiments measured learning for three cues: POSN (position cue), TRANSL (translation cue), and SOUND (sound cue). Each data point is based on seven to eight test trials per trainee (62-64 judgments per data point). Error bars are 67% confidence intervals for binomially distributed data. Data were included only for those trainees who completed all sessions of their experiment (eight different trainees per experiment). Cue contingency was reversed on day 2 in the POSN experiment (POSN-REV) and on day 3 in the TRANSL experiment (TRANSL-REV). The dashed curves replot the data from day 1 of the POSN and TRANSL experiments, reflected about the 50% line. New trainees, if run in the POSN-REV and TRANSL-REV conditions, would be expected to produce data along these dashed curves.

Fig. 3.

Effect of training on day 1. The percentage of test trials judged to have right-handed rotation is shown for the three experiments (POSN, TRANSL, and SOUND) and lasted 2, 3, and 1 day(s), respectively; only day 1 is shown in this figure. Different trainees were used for each experiment. Trainees in each experiment were divided into two groups that received exposure to opposite signal contingency (on either side of the vertical dashed line in the middle of the graph). For POSN, right-hand rotation (RHR) was paired with placement of the rotating cube in the top or bottom of the display. For TRANSL, RHR was paired with upward or downward translation of the cube. For SOUND, RHR was paired with a high- or low-pitched tone sequence. The height difference between the solid and hatched bars indicates the biasing effect caused by training. The significance of this difference is expressed as a P value for a χ² test, shown above each trainee's data.

Fig. 4.

Persistence of learning into the next day. The data plotted are the percentage of trials on which the perceived rotation direction agreed with the new signal, according to its contingency that day. Each pair (Upper) or triplet (Lower) of bars represents data from one trainee. A bar height >50% means the cue was effective in the predicted direction. If trainees started each day in the same state, bar heights would be the same on all days for a given trainee, which was not the case. Instead, continued training on day 2 (TRANSL) resulted in additional bias, and reversed training on day 2 (POSN) or day 3 (TRANSL) resulted in less bias (in the new predicted direction) as compared with that seen on day 1. T tests for the between-day differences (across trainees) were as follows: (i) for POSN, H₀ (null hypothesis): day 1 = day 2 was rejected at P < 0.001; (ii) for TRANSL, H₀: day 1 = day 2 was rejected at P < 0.05; and (iii) for TRANSL, H₀: day 2 = day 3 was rejected at P < 0.001. Only those trainees who completed all sessions of their experiment are shown.