Table 7.
Effect sizes for Contextual Manipulations: Estimated subcategory averages (and SEM) from the Contextual manipulation-only meta-analytic mode and individual-publication effect sizes.
| Subcategory or Study |
Population | Manipulation | DV | Effect on Impulsivity |
Effect Size | p | |
|---|---|---|---|---|---|---|---|
| Adding Delays | 0.49 (.08) | <.001 | |||||
| Ainslie & Herrnstein (1981) | Pigeons | Added 4-s delay (vs. no added delay) | %LLR | ↓ | ‡ | ||
| Added 12-s delay (vs. no added delay) | ↓ | ‡ | |||||
| Dai & Fishbach (2013) Experiments 1–2b | College students | Added delay (vs. small added delay) | Proportion choosing LLR | ↓ | 0.40*◊ | ||
| Same, but choice made when delay to SSR 90% complete (vs. small added delay) | ↓ | 0.70* | |||||
| Green et al. (2005)§ Experiments 1–2 | College students | Added 2-year delay (vs. no added delay) | AUC | ↓ | −0.01*# | ||
| Added 5-year delay (vs. no added delay) | ↓ | 0.39*# | |||||
| Added 10-year delay (vs. no added delay) | ↓ | 0.66*# | |||||
| Mitchell & Wilson (2012) Experiments 1–2 | Nonsmokers | Added 12-week delay (vs. no added delay) | k | ↓ | n.s. | 0.37* | |
| Smokers | ↓ | 0.75* | |||||
| Rachlin & Green (1972) | Pigeons | Added 4-s delay (vs. no added delay) | Relative response rate | ↓ | ‡ | ||
| Added 12-s delay (vs. no added delay) | ↓ | ‡ | |||||
| Seigel & Rachlin (1995) | Pigeons | Added delay (vs. no added delay) | %SSR | ↓ | 1.47 | ||
| Adding Response Requirements | 2.14 (1.17) | .07 | |||||
| Fortes et al. (2015) | Pigeons | High response rate during LLR delay (vs. no responding during delay) | Indifference delay | ↓ | ‡ | ||
| Low response rate during LLR delay (vs. no responding during delay) | ↑ | ‡ | |||||
| Huskinson & Anderson (2013) | Rats | High pre-choice response requirement (vs. single response) | AUCb | ↓ | 3.03 | ||
| Half of the pre-choice response requirement (vs. single-response) | ↓ | 2.16 | |||||
| Mazur (2012) | Rats | Pre-choice response requirement (vs. single response) | %LLR | ↓ | ‡ | ||
| Pigeons | — | ‡ | |||||
| Seigel & Rachlin (1995) | Pigeons | Pre-choice response requirement (vs. single response) | %LLR | ↓ | 1.59* | ||
| Adding Outcomes (vs. no added outcome) | 0.24 (0.06) | < .001 | |||||
| Kowal & Faulkner (2015) | College students | Added decoy LLR alternative | k | ↓ | 0.16◊* | ||
| Added decoy SSR/LLR alternative | k | ↓ | 0.11 | ||||
| Scholten & Read (2014) | Online volunteers | Improving sequence (LLR) | Proportion choosing LLR | ↓ | 0.17* | ||
| Deteriorating sequence (SSR) | ↓ | 0.49* | |||||
| Urminsky & Kivetz (2011)˚ | Adults | Add small, near-immediate reward to SSR and LLR | Proportion choosing & preference for | ↓ | 0.22◊* | ||
| Trustworthiness | 0.76 (0.17) | < .001 | |||||
| Mahrer (1956) | Stimulant addicts | Working memory training (vs. sham) | Proportion choosing LLR | ↓ | 0.60 | ||
| Michaelson et al. (2013) | Online volunteers | Trustworthy LLR provider (vs. neutral provider) | Probability of choosing LLR | ↓ | 1.29 (within-Ss) | ||
| ↑ | n.s. | 0.12 (between-Ss) | |||||
n.s., No statistically significant effect; AUC, area under the discounting curve
The effect of the added delay was examined using an ANOVA, with the no-added delay as the reference condition; there was a main effect of added-delay, but post-hoc tests were not reported (and thus, statistical significance for each added delay in the table is unknown).
The effect sizes for the $10k and $100k LLRs were omitted from the meta-analysis (>3 effect sizes in the same subjects) but are included in the averages presented in the table.
Effect sizes from Exp 1b ($50 and $100 token amounts), Exp 3, and Exp 5a ($100, $300, $700, and $900) were omitted from the meta-analysis (>8 effect sizes from the same publication) but are included in the averages presented in the table.
Effect sizes were not calculated due to small sample size.
Effect sizes averaged across experiments or comparable conditions.
Average is a combination of significant and non-significant effects.