Omissions as possibilities

I present and develop the view that omissions are de re possibilities of actual events. Omissions do not literally fail to occur; rather, they possibly occur. An omission is a tripartite metaphysical entity composed of an actual event, a possible event, and a contextually specified counterpart relation between them. This view resolves ontological, causal, and semantic puzzles about omissions, and also accounts for important data about moral responsibility for outcomes resulting from omissions.     

The omission strategy

People are more willing to bring about morally objectionable outcomes by omission than by commission. Similarly, people condemn others less harshly when a moral offense occurs by omission rather than by commission, even when intentions are controlled. We propose that these two phenomena are related, and that the reduced moral condemnation of omissions causes people to choose omissions in their own behavior to avoid punishment. We report two experiments using an economic game in which one participant (the taker) could take money from another participant (the owner) either by omission or by commission. We manipulated whether or not a third party had the opportunity to punish the taker by reducing the taker's payment. Our results indicated that the frequency of omission increases when punishment is possible. We conclude that people choose omissions to avoid condemnation and that the omission effect is best understood not as a bias, but as a strategy.     

Is there really an omission effect?

The omission effect, first described by Spranca and colleagues (Spranca, Minsk, & Baron, 1991), has since been extensively studied and repeatedly confirmed (Cushman, Murray, Gordon-McKeon, Wharton, & Greene, 2012). All else being equal, most people judge it to be morally worse to actively bring about a negative event than to passively allow that event to happen. In this paper, we provide new experimental data that challenges previous studies of the omission effect both methodologically and philosophically. We argue that previous studies have failed to control for the equivalence of rules that are violated by actions and omissions. Once equivalent norms are introduced, our results show that the omission effect is eliminated, even if the negative outcome of the behavior is foreseen and intended by the agent. We show that the omission effect does not constitute a basic, moral disposition but occurs exclusively in complex moral situations. Building on these empirical results, we cast doubt onto two influential explanations of the omission effect, the Causal Relevance Hypothesis and the Overgeneralization Hypothesis, and provide a novel explanation of the phenomenon. Furthermore, we discuss various ramifications of the interplay between our understanding of omissions and legal systems.     

Outcome Knowledge,Regret, and Omission Bias

Subjects made or evaluated decisions in hypothetical scenarios. We manipulated knowledge about the outcome and act vs omission in four cases. In case 1 (production processes), acts (changing the process) were considered better than omissions when the decision maker did not know the outcome or knew that it was better than the status quo. Acts were considered worse than omissions once the decision maker learned that the foregone option would have led to an even better outcome. In case 2 (medical treatment), act vs omission again interacted with gain vs loss (relative to the status quo) unless the outcome of the foregone option was known, in which case act vs omission interacted with better vs worse (of the two options). In case 3 (fetal testing), subjects tolerated less risk of miscarriage when a potential for regret was present (because the test with the risk of miscarriage, although better, might miss disorders that another test would detect). This effect was greater for actions than omissions. In case 4 (vaccination), subjects showed less tolerance of vaccine risk when the decision maker would know about the outcome of vaccination or nonvaccination. Thus, the bias toward omission (not vaccinating) is greater when potential regret is present, and potential regret is greater when knowledge of outcomes is expected.     

The Role of Omission Neglect in Response to Non-Gains and Non-Losses in Gasoline Price Fluctuations

Research on omission neglect has shown that people are insensitive to many different types of missing, unmentioned, or unknown information. However, prior research has not examined the role of omission neglect in non-gain and non-loss framing. The present research shows that gain/loss framing effects are greater than non-gain/non-loss framing effects on judgments of the ease with which various scenarios can be imagined, judgments of believability, attributions to price gouging, and attributions to inflation. The results also show that negative outcomes are more influential than are positive outcomes in judgments of imaginability, believability, and fairness, and in attribution judgments. Considered together, the results suggest that omission neglect plays an important role in insensitivity to non-gains and non-losses.     

Protected values: No omission bias and no framing effects

Previous studies have suggested that people holding protected values (PVs) show a bias against harmful acts, as opposed to harmful omissions (omission bias). In the present study, we (1) investigated the relationship between PVs and acts versus omissions in risky choices, using a paradigm in which act and omission biases were presented in a symmetrical manner, and (2) examined whether people holding PVs respond differently to framing manipulations. Participants were given environmental scenarios and were asked to make choices between actions and omissions. Both the framing of the outcomes (positive vs. negative) and the outcome certainty (risky vs. certain) were manipulated. In contrast to previous studies, PVs were linked to preferences for acts, rather than for omissions. PVs were more likely to be associated with moral obligations to act than with moral prohibitions against action. Strikingly, people with strong PVs were immune to framing; participants with few PVs showed robust framing effects.     

Perception mirrors production in 14- and 18-month-olds: the case of coda consonants

In a word learning experiment, 14- and 18-month-old infants are tested on their perceptual sensitivity to coda-consonant omissions. The results indicate that 14-month-olds are not sensitive to coda consonant omissions, showing a parallel with the omission of target coda consonants in early child language productions. At 18 months, infants are sensitive to coda-omission. The study strengthens the hypothesis that phonological wellformedness constraints influence infants' speech processing in general, and might restrict what is stored in their initial lexical representations. A lexical representation lacking information on the target coda consonant is, in turn, a likely source for coda-omissions in production.     

Probability and category redefinition in the fault tree paradigm

Fault trees have been advocated as aids for problem solvers. However, research has suggested limitations in their usefulness. Fischhoff, Slovic, and Lichtenstein (1978) found that subjects given incomplete (pruned) trees were insensitive to omissions; these authors hypothesized that Tversky and Kahneman's (1974) availability heuristic was the mediating factor. Using a within-subjects design, subjects in Experiment 1 received both full and pruned trees and estimated probabilities for various reasons why a car would fail to start. To increase the availability of omissions, some Experiment 1 subjects first generated possible causes of starting failure. The basic Fischhoff et al. findings were replicated, but several aspects of the results argued against the availability hypothesis as the mechanism for judgment. Instead, subjects appeared to idiosyncratically redefine category membership when making judgments based upon pruned trees. By employing a sorting task in Experiment 2 we corroborated the results of Experiment 1: Subjects do redefine the actual contents of the categories when faced with an omission from the fault tree. The implications of these results for the use of fault trees as a problem solving aid are discussed.     

Drawing perseveration in neglect: Effects of target density

In cancellation tasks, patients with unilateral spatial neglect typically fail to mark targets within the side of the sheet contralateral to the side of the lesion (contralesional). Moreover, they can show a perseverative behaviour, which consists in repeatedly cancelling stimuli, mainly in the side of the display ipsilateral to the side of the lesion (ipsilesional). We investigated in 13 right‐brain‐damaged patients with left spatial neglect and perseverative behaviour whether and how different densities of horizontal targets modulated omission and perseverative errors. We found that the density of targets modulated the patients’ distribution of neglect (area of omission), but not its extent, as indexed by the percentage of omissions. Specifically, the area of omissions tightened when target density increased leftwards. On the other hand, target density did not affect the distribution of perseverative behaviour (area of perseveration), as well as its extent, as indexed by the percentage of perseverations. Correlation analyses showed that both the extent and the distribution of omissions were positively correlated to clinical measures of spatial neglect. Conversely, perseverations did not show such a correlation. These findings support the view that two different pathological mechanisms might be involved in left spatial neglect and in ipsilesional perseverative behaviour.     

Responsibility, Control, and Omissions

Previously, I have argued that moral responsibility for actions is associated with guidance control. This sort of control does not necessarily involve the freedom to do otherwise. In this paper I extend the view to apply to omissions. That is, moral responsibility for an omission is associated with guidance control of that omission. This helps to provide a systematic, unified account of moral responsibility.     

The interaction of word frequency and word class: a test of the GO model's account of the missing-letter effect

When asked to detect target letters while reading a text, participants miss more letters in frequent function words than in less frequent content words. In this phenomenon, known as the missing-letter effect, two factors covary: word frequency and word class. According to the GO model, there should be an interaction between word class and word frequency with more omissions for function than for content words only among high-frequency words. This pattern would be due to the fact that function words could only assume a structure-supporting role if they are identified rapidly, which is only possible for high-frequency words. These predictions were tested by assessing omission rate for frequent and rare function and content words. Results lend support to the GO model with more omissions for frequent than for rare words, and more omissions for the function than for the content word among high-frequency words, but not among low-frequency words. These results were observed both in English (Experiment 1) and in French (Experiment 2).     

Reference Points and Omission Bias

Subjects were asked to evaluate the choice of options leading to known outcomes, or to say how they would feel about a chance outcome, in hypothetical decisions. We independently manipulated the value of the status quo and the assignment of the better or worse outcome to an act or an omission. Acts leading to the worse outcome were always considered worse than omissions leading to the worse outcome. This act-omission difference was reduced or reversed for the better outcome. Most experiments showed an overall bias toward omissions (combining better and worse). Little evidence was found for greater omission bias for losses relative to the status quo than for gains. A bias toward maintaining the status quo itself was found, however, independently of omission bias. Most of the results can be explained by norm theory and by loss aversion, but other possible accounts are inconsistent with the results.     

Children's moral judgments of commission and omission based on their understanding of second‐order mental states1

Abstract: Children's moral judgments about acts of commission and omission with negative outcomes were studied based on their understanding of mental states. Children (N = 142) in the first, third, and fifth grades made judgments about four tasks composed of two levels of mental states (first‐order or second‐order) and two types of acts (commission or omission). The results showed that the 7‐year‐olds responded considering only first‐order mental states, but the 9‐ and 11‐year‐olds also used second‐order mental states in their judgments. Whether the acts were commission or omission did not make a difference. These results indicate that children can make moral judgments regarding acts of commission and omission based on an understanding of second‐order mental states by approximately the age of 9 years.     

The interaction of word frequency and word class: A test of the GO model's account of the missing-letter effect

When asked to detect target letters while reading a text, participants miss more letters in frequent function words than in less frequent content words. In this phenomenon, known as the missing-letter effect, two factors covary: word frequency and word class. According to the GO model, there should be an interaction between word class and word frequency with more omissions for function than for content words only among high-frequency words. This pattern would be due to the fact that function words could only assume a structure-supporting role if they are identified rapidly, which is only possible for high-frequency words. These predictions were tested by assessing omission rate for frequent and rare function and content words. Results lend support to the GO model with more omissions for frequent than for rare words, and more omissions for the function than for the content word among high-frequency words, but not among low-frequency words. These results were observed both in English (Experiment 1) and in French (Experiment 2).     

Social roles and the moral judgement of acts and omissions

Three experiments investigated how moral judgements of harmful acts and omissions are affected by information about social roles. Subjects were given vignettes in which the relationship between an actor and victim was varied along the dimensions of solidarity (e.g. friends versus strangers) and hierachy (e.g. superior versus equal; the terms are from Hamilton & Sanders, 1981). Subjects were asked to judge the morality of the actor in each case, both for a harmful omission (e.g. intentionally withholding the truth) and for an equivalent act (e.g. actively lying). Subjects judged the behaviour worse in the act than the omission. Judgements were also affected by role relationships. The act–omission difference was also greater in the low-responsibility roles. Responses to the high-responsibility roles seem to reflect in a consequentialist perspective, focusing on outcomes rather than prohibitions.     

Contrastive explanation and the many absences problem

We often explain by citing an absence or an omission. Apart from the problem of assigning a causal role to such apparently negative factors as absences and omissions, there is a puzzle as to why only some absences and omissions, out of indefinitely many, should figure in explanations. In this paper we solve this ’many absences problem’ by using the contrastive model of explanation. The contrastive model of explanation is developed by adapting Peter Lipton’s account. What initially appears to be only a trivial amendment to Lipton’s Difference Condition enables us both to offer a much more satisfactory solution to the ’many absences problem’ than David Lewis did, and also to explain why explanation in terms of absences and omissions should be so common.     

Numbers,thoughts, and things: The Ontology of numbers for children and adults

Keil's predicability method for studying ontological categories was adapted to examine the conceptions of numbers of 5-year-old children versus adults. Our primary focus was on the ontological distinction between numbers and sets of objects, which is clearly in place by age 5 and continues to organize adults' ontological judgments about numbers. Children, like, adults, attribute spatial-arrangement properties to collections much more than to numbers, although they see both numbers and collections as having quantitative properties. Children were also similar to adults in that they equated numbers more closely with their written representations (numerals) than with spoken representations (number words).     

A case of collective responsibility: who else was to blame for the Columbine high school shootings?

Two studies examined perceptions of collective responsibility for the April 20, 1999, shootings at Columbine High School in Littleton, Colorado. Collective responsibility refers to the perception that others, besides the wrongdoers themselves, are responsible for the event. In Study 1, the authors assessed perceptions of the shooters' parents and their peer group (the Trenchcoat Mafia), whereas Study 2 tested perceptions of collective responsibility across a range of groups. In both studies, perceptions of a target group's entitativity predicted judgments of collective responsibility. This relationship was mediated by two situational construals that justify applying collective responsibility: responsibility by commission (encouraging or facilitating the event) and responsibility by omission (failing to prevent the event). Study 2 also determined that perceptions of authority predicted judgments of collective responsibility for the Columbine shootings and was mediated by inferences of omission. Future directions in collective responsibility research are discussed.     

The influence of multiple readings on the missing-letter effect revisited

In searching for a target letter while reading, participants make more omissions when the target letter is embedded in frequent function words than when it is embedded in less frequent content words. According to the guidance-organization (GO) model, this occurs because high-frequency function words are processed faster than low-frequency content words, leaving less time available for letter processing. We tested this hypothesis in three experiments by increasing word-processing speed through text repetition, which should translate into higher omission rates. Participants either read the text and searched for the target letter once or read the text three times and searched for a target letter on all readings or the final reading only. In all the experiments in which participants could not anticipate the target letter to be used, results revealed the presence of a large missing-letter effect that was unaffected by familiarity with the text. In addition, when participants knew from the start the target letter to be used on the final reading, the missing-letter effect was eliminated. Repeated search of the same text for different targets increased omissions equally for function words and content words, but this finding was present even when a new text was used, suggesting that repetition of the search task, rather than familiarity with the text, was responsible.     

Young children's moral judgments of commission and omission related to the understanding of Knowledge or Ignorance

This study examined developmental change in young children's moral judgments of commission and omission related to mental states, especially knowledge or ignorance. 4–5 and 5‐ to 6‐year‐olds (n=67) made moral judgments about the tasks related to the understanding of knowledge or ignorance. The tasks were also composed of two types of acts: commission or omission. The results showed that the both age groups understood knowledge and ignorance, but that the older group made moral judgments based on this understanding more similar to adults compared to the younger group. There was not an age difference concerning whether the acts were of commission or omission. These findings indicate that there is no difference for young children in the difficulty in moral judgments of acts of commission and omission related to mental states, whereas there is a developmental difference in using the understanding of knowledge or ignorance for making moral judgments. Copyright © 2009 John Wiley & Sons, Ltd.