Participants
Demographic data are in Table 1.
Encoding
Mean±SD encoding accuracy was exceptionally high (99.1±1.4%).
Memory
The effect of PictureType on d′ was significant, F(2, 92) = 41.7, p < .001, η²G = 0.16. Pairwise comparisons showed that d’ was higher for negative pictures (1.34±0.67) vs. both neutral (0.74±0.46) and positive (1.11±0.53) pictures, ts > 3, ps < .02; d’ was also higher for positive vs. neutral pictures, t(46) = 6.6, p < .001. The effect of PictureType on c was also significant, F(2, 92) = 7.20, p = .002, η²G = 0.04. Pairwise tests indicated that c was lower for negative pictures (0.22±0.35) vs. both neutral (0.38±0.37) and positive (0.34±0.27) pictures, ts < -2.8, ps < .02. c did not differ reliably for neutral and positive pictures, t(46) = 1.09, p = .84. To summarize, discriminability was generally good—best for negative pictures and worst for neutral pictures—and participants showed a bias to respond “new” (all values of c > 0) that was weakest for negative pictures. These analyses confirmed that memory was sufficiently accurate to permit examination of its effect on subjective experience.
Pictures Elicited Expected Emotions
Before considering the impact of memory on emotion, we examined the effect of PictureType on valence and arousal ratings to confirm that pictures elicited the expected emotions. The ANOVA on valence ratings was highly significant, F(2, 92) = 380.28, p < .001, η²G = .86. Valence ratings were lowest for negative pictures (20.3 ± 17.0), intermediate for neutral (47.8 ± 11.8), and highest for positive pictures (75.7 ± 16.7). All pairwise comparisons were significant, ps < .001.
The ANOVA on arousal ratings was also significant, F(2, 92) = 96.75, p < .001, η²G = .52. As intended, arousal levels were similar for negative (65.3±24.6) and positive (62.1±22.4) pictures, but lower for neutral pictures (24.5±23.4). Pairwise comparisons confirmed no difference between negative and positive pictures, t(46) = 1.30, p = .603, d = 0.14, but significant differences between negative and neutral pictures, t(46) = -10.45, p < .001, d = 1.7, and between positive and neutral pictures, t(46) = -11.78, p < .001, d = 1.64.
Effect of Memory on Valence Ratings
Figure 1 shows that the impact of memory on valence ratings varied by picture type. For neutral and positive pictures valence was higher for Hits vs. CRs, but for negative pictures valence ratings were lower for Hits vs. CRs.
A linear mixed model for netural pictures confirmed higher valence ratings for Hits vs. CRs (b = 1.01, SE = 0.36, z = 2.84, p = .005, d = 0.12). No differences were observed between Hits and FAs (b = −0.50, SE = 0.48, z = −1.03, p = .304, d = 0.05) or between FAs and CRs (b = 0.52, SE = 0.47, z = 1.10, p = .271, d = -0.05).
For positive pictures, Hits again received higher valence ratings than CRs (b = 1.80, SE = 0.43, z = 4.18, p < .001, d = 0.21). No difference emerged between Hits and FAs (b = −0.53, SE = 0.66, z = −0.80, p = .426, d = -0.17), but FAs received higher valence ratings than CRs (b = 2.33, SE = 0.65, z = 3.58, p < .001, d = 0.38).
For negative pictures, Hits received lower valence ratings than CRs (b = −0.94, SE = 0.45, Z = −2.10, p = .036, d = -0.18). No differences emerged between Hits and FAs (b = −0.11, SE = 0.69, z = −0.16, p = .873, d = -0.14) or between FAs and CRs (b = 0.83, SE = 0.69, z = 1.20, p = .230, d = 0.01). Descriptive data are in Table 21.
Arousal
Figure 2 shows that Hits were more arousing than CRs for neutral pictures (b = 1.90, SE = 0.52, Z = 3.64, p < .001, d = 0.08), positive pictures (b = 2.69, SE = 0.51, z = 5.25, p < .001, d = 0.18), and negative pictures (b = 1.53, SE = 0.55, z = 2.78, p = .005, d = 0.1).
Confidence
Figure 3 shows that confidence modulated the strength of the Hit–CR effect on valence ratings elicited by emotional pictures (neutral pictures were excluded from this analysis). This impression was supported by a significant PictureType x Confidence interaction (b = 5.22, SE = 2.55, t(257) = 2.04, p = .042, η²G = 0.02). For high confidence responses, the Hit-CR subtraction yielded higher valence ratings for positive vs. negative pictures (b = 4.42, SE = 1.75, t(257) = 2.53, p = .01, d = 0.62). This effect was not significant, however, for medium (b = -1.1, SE = 1.74, t(257) = -0.63, p = 1, d = 0.12) or low confidence responses (b = 0.79, SE = 1.86, t(257) = 0.43, p = 1, d = 0.09).