207 research outputs found
Counterfactual thinking about actions and failures to act
When people think counterfactually about how a situation could have turned out differently, they mentally undo events in regular ways (e.g., they focus on actions not failures to act). Four experiments examine the recent discovery that the focus on actions in the short term switches to inactions in the long term. The experiments show that this temporal switch occurs only for particular sorts of situations. Experiment 1 showed no temporal pattern to die agency effect when 112 participants judged emotional impact and frequency of "if-only " thoughts from both short- and long-term perspectives for an investment scenario. Experiment 2 showed no temporal pattern when 190 participants considered a college choice scenario with a good outcome. Experiment 3 showed no temporal pattern when 131 participants considered an investment scenario even when the situation for the actor and nonactor was bad from the outset. Experiment 4, with 113 participants, showed a focus on actions even when the investment loss was equal for both the actor and nonactor. The implications of the results are discussed in terms of what is explicitly available in the mental representation of actions and inactions. Counterfactual thinking about how factual situations may have been different occurs often in everyday thinking (e.g., Kahneman & Miller, 1986). People spontaneously think about how an outcom
Features of Explainability: How users understand counterfactual and causal explanations for categorical and continuous features in XAI
Counterfactual explanations are increasingly used to address
interpretability, recourse, and bias in AI decisions. However, we do not know
how well counterfactual explanations help users to understand a systems
decisions, since no large scale user studies have compared their efficacy to
other sorts of explanations such as causal explanations (which have a longer
track record of use in rule based and decision tree models). It is also unknown
whether counterfactual explanations are equally effective for categorical as
for continuous features, although current methods assume they do. Hence, in a
controlled user study with 127 volunteer participants, we tested the effects of
counterfactual and causal explanations on the objective accuracy of users
predictions of the decisions made by a simple AI system, and participants
subjective judgments of satisfaction and trust in the explanations. We
discovered a dissociation between objective and subjective measures:
counterfactual explanations elicit higher accuracy of predictions than
no-explanation control descriptions but no higher accuracy than causal
explanations, yet counterfactual explanations elicit greater satisfaction and
trust than causal explanations. We also found that users understand
explanations referring to categorical features more readily than those
referring to continuous features. We discuss the implications of these findings
for current and future counterfactual methods in XAI.Comment: 26 pages, 7 figures, appendi
RaciocĂnio contrafactual e modelos mentais
A ideia central deste estudo é de que «... raciocinar
sobre factos e raciocinar sobre possibilidades e impossibilidades,
baseia-se nos mesmos tipos de representaçÔes
mentais e processos cognitivos» (Byrne, 1997,
p. 107). Quer dizer que as pessoas raciocinam através
da construção e revisão de modelos mentais (e.g.,
Johnson-Laird, Byrne, 1991).
As condicionais contrafactuais requerem que os
raciocinadores tenham em mente nĂŁo apenas o que Ă©
suposto ser verdadeiro, mas também o que é supostamente
verdadeiro mas factualmente falso (Byrne,
1997, p. 117; cf. Johnson-Laird, Byrne, 1991, pp. 72-
-73). E a hipótese de que a representação inicial de
uma condicional contrafactual Ă© mais explĂcita do
que a de uma condicional factual, permite prever que
as inferĂȘncias Modus Tollens e Negação do Antecedente
deverĂŁo ser feitas com maior frequĂȘncia a partir
das condicionais contrafactuais do que das factuais.
Byrne e Tasso (in press) encontraram evidĂȘncia para
esta hipĂłtese.
No estudo que apresentamos, também procuramos
replicar esses resultados encontrados por Byrne e
Tasso, e acrescentamos algumas hipĂłteses relacionadas
com as latĂȘncias para compreender os dois tipos de
condicionais, e para escolher a conclusĂŁo. Utilizamos
condicionais neutras do tipo «Se houve um cĂrculo,
então houve um triùngulo», e apresentamos aos participantes
os quatro silogismos condicionais no programa
SUPERLAB.The central idea in this study is that «... thinking
about matters of fact and thinking about matters of
possibility and impossibility are based on similar sorts
of mental representations and cognitive processes»
(Byrne, 1997, p. 107). That is to say that people reason
by constructing and revising mental models (e.g.,
Johnson-Laird, & Byrne, 1991).
Counterfactual conditionals require reasoners to
keep in mind not only what is presupposed to be true,
but also what is suppositionally true but factually false
(Byrne, 1997, p. 117; cf. Johnson-Laird, & Byrne,
1991, pp. 72-73). And the hypothesis that the initial
representation of a counterfactual conditional is more
explicit than the initial representation of a factual conditional,
allows the prediction that Modus Tollens and
Denial of the Antecedent inferences would be made
more frequently from the counterfactual than from the
factual conditionals. Byrne and Tasso (in press) found
evidence for those predictions.
In the present study, we look for replication of the
data found by Byrne and Tasso, and we add some
hypothesis related with the latencies to understand
both kinds of conditionals, and to choose a conclusion.
We use neutral conditionals like «If there was a circle,
then there was a triangle», and we presented to participants
the four conditional syllogisms in the
SUPERLAB program
Reasoning with deontic and counterfactual conditionals
We report two new phenomena of deontic reasoning: (1) For conditionals with
deontic content such as, âIf the nurse cleaned up the blood then she must have
worn rubber glovesâ, reasoners make more modus tollens inferences (from âshe
did not wear rubber glovesâ to âshe did not clean up the bloodâ) compared to
conditionals with epistemic content. (2) For conditionals in the subjunctive mood
with deontic content, such as, âIf the nurse had cleaned up the blood then she must
have had to wear rubber glovesâ, reasoners make the same frequency of all
inferences as they do for conditionals in the indicative mood with deontic content.
In this regard, subjunctive deontics are different from subjunctive epistemic
conditionals: reasoners interpret subjunctive epistemic conditionals as counterfactual
and they make more negative inferences such as modus tollens from them.
The experiments show these two phenomena occur for deontic conditionals that
contain the modal auxiliary âmustâ and ones that do not. We discuss the results in
terms of the mental representations of deontic conditionals and of counterfactual
conditionals
Enhanced perfusion following exposure to radiotherapy: a theoretical investigation
Tumour angiogenesis leads to the formation of blood vessels that are structurally and spatially heterogeneous. Poor blood perfusion, in conjunction with increased hypoxia and oxygen heterogeneity, impairs a tumourâs response to radiotherapy. The optimal strategy for enhancing tumour perfusion remains unclear, preventing its regular deployment in combination therapies. In this work, we first identify vascular architectural features that correlate with enhanced perfusion following radiotherapy, using in vivo imaging data from vascular tumours. Then, we present a novel computational model to determine the relationship between these architectural features and blood perfusion in silico. If perfusion is defined to be the proportion of vessels that support blood flow, we find that vascular networks with small mean diameters and large numbers of angiogenic sprouts show the largest increases in perfusion post-irradiation for both biological and synthetic tumours. We also identify cases where perfusion increases due to the pruning of hypoperfused vessels, rather than blood being rerouted. These results indicate the importance of considering network composition when determining the optimal irradiation strategy. In the future, we aim to use our findings to identify tumours that are good candidates for perfusion enhancement and to improve the efficacy of combination therapies
Genetic predisposition to metabolically unfavourable adiposity and prostate cancer risk:A Mendelian randomization analysis
BACKGROUND
The associations of adiposity with aggressive prostate cancer risk are unclear. Using two-sample Mendelian randomization, we assessed the association of metabolically unfavourable adiposity (UFA), favourable adiposity (FA) and for comparison body mass index (BMI), with prostate cancer, including aggressive prostate cancer.
METHODS
We examined the association of these genetically predicted adiposity-related traits with risk of prostate cancer overall, aggressive and early onset disease using outcome summary statistics from the PRACTICAL consortium (including 15,167 aggressive cases).
RESULTS
In inverse-variance weighted models, there was little evidence that genetically predicted one standard deviation higher UFA, FA and BMI were associated with aggressive prostate cancer [OR: 0.85 (95% CI:0.61-1.19), 0.80 (0.53-1.23) and 0.97 (0.88-1.08), respectively]; these associations were largely consistent in sensitivity analyses accounting for horizontal pleiotropy. There was no strong evidence that genetically determined UFA, FA or BMI were associated with overall prostate cancer or early age of onset prostate cancer.
CONCLUSIONS
We did not find differences in the associations of UFA and FA with prostate cancer risk, which suggest that adiposity is unlikely to influence prostate cancer via the metabolic factors assessed; however, these did not cover some aspects related to metabolic health that may link obesity with aggressive prostate cancer, which should be explored in future studies
Length versus radius relationship for ZnO nanowires grown via vapour phase transport
We model the growth of ZnO nanowires via vapour phase transport and examine the relationship predicted between the nanowire length and radius. The model predicts that the
lengths of the nanowires increase with decreasing nanowire radii. This prediction is in very good agreement with experimental data from a variety of nanowire samples, including samples showing a broad range of nanowire radii and samples grown using a lithographic technique to constrain the nanowire radius. The close agreement of the model and the experimental data strongly support supporting the inclusion of a surface diffusion term in the model for the incorporation of species into a growing nanowire
Enhanced perfusion following exposure to radiotherapy: a theoretical investigation
Tumour angiogenesis leads to the formation of blood vessels that are structurally and spatially heterogeneous. Poor blood perfusion, in conjunction with increased hypoxia and oxygen heterogeneity, impairs a tumourâs response to radiotherapy. The optimal strategy for enhancing tumour perfusion remains unclear, preventing its regular deployment in combination therapies. In this work, we first identify vascular architectural features that correlate with enhanced perfusion following radiotherapy, using in vivo imaging data from vascular tumours. Then, we present a novel computational model to determine the relationship between these architectural features and blood perfusion in silico. If perfusion is defined to be the proportion of vessels that support blood flow, we find that vascular networks with small mean diameters and large numbers of angiogenic sprouts show the largest increases in perfusion post-irradiation for both biological and synthetic tumours. We also identify cases where perfusion increases due to the pruning of hypoperfused vessels, rather than blood being rerouted. These results indicate the importance of considering network composition when determining the optimal irradiation strategy. In the future, we aim to use our findings to identify tumours that are good candidates for perfusion enhancement and to improve the efficacy of combination therapies
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