Query: The iris hypothesis has not withstood the test of time - subsequent research

Relevant passages:
Type I and type II errors <=SEP=> In statistical hypothesis testing , a type I error is the incorrect rejection of a true null hypothesis ( a `` false positive '' ) , while a type II error is incorrectly retaining a false null hypothesis ( a `` false negative '' ) . More simply stated , a type I error is detecting an effect that is not present , while a type II error is the failure to detect an effect that is present .

Confirmation bias <=SEP=> Confirmation bias , also called confirmatory bias or myside bias , David Perkins , a geneticist , coined the term `` myside bias '' referring to a preference for `` my '' side of an issue . is the tendency to search for , interpret , favor , and recall information in a way that confirms one 's preexisting beliefs or hypotheses . It is a type of cognitive bias and a systematic error of inductive reasoning . People display this bias when they gather or remember information selectively , or when they interpret it in a biased way . The effect is stronger for emotionally charged issues and for deeply entrenched beliefs . People also tend to interpret ambiguous evidence as supporting their existing position . Biased search , interpretation and memory have been invoked to explain attitude polarization ( when a disagreement becomes more extreme even though the different parties are exposed to the same evidence ) , belief perseverance ( when beliefs persist after the evidence for them is shown to be false ) , the irrational primacy effect ( a greater reliance on information encountered early in a series ) and illusory correlation ( when people falsely perceive an association between two events or situations ) .   A series of experiments in the 1960s suggested that people are biased toward confirming their existing beliefs . Later work re-interpreted these results as a tendency to test ideas in a one-sided way , focusing on one possibility and ignoring alternatives . In certain situations , this tendency can bias people 's conclusions . Explanations for the observed biases include wishful thinking and the limited human capacity to process information . Another explanation is that people show confirmation bias because they are weighing up the costs of being wrong , rather than investigating in a neutral , scientific way .   Confirmation biases contribute to overconfidence in personal beliefs and can maintain or strengthen beliefs in the face of contrary evidence . Poor decisions due to these biases have been found in political and organizational contexts.Tuchman ( 1984 ) described a form of confirmation bias at work in the process of justifying policies to which a government has committed itself : `` Once a policy has been adopted and implemented , all subsequent activity becomes an effort to justify it '' ( p. 245 ) .   In the context of a discussion of the policy that drew the United States into war in Vietnam and kept the U.S. military engaged for 16 years despite countless evidences that it was a lost cause from the beginning , Tuchman argued :   Wooden-headedness , the source of self-deception is a factor that plays a remarkably large role in government . It consists in assessing a situation in terms of preconceived fixed notions while ignoring or rejecting any contrary signs . It is acting according to wish while not allowing oneself to be deflected by the facts . It is epitomized in a historian 's statement about Philip II of Spain , the surpassing wooden head of all sovereigns : `` no experience of the failure of his policy could shake his belief in essential excellence . '' ( p. 7 )  Folly , she argued , is a form of self-deception characterized by `` insistence on a rooted notion regardless of contrary evidence '' ( p. 209 )

Cretaceous–Paleogene extinction event <=SEP=> The Cretaceous -- Paleogene ( K -- Pg ) extinction event , also known as the Cretaceous -- Tertiary ( K -- T ) extinction , was a mass extinction of some three-quarters of the plant and animal species on Earth that occurred over a geologically short period of time approximately 65 million years ago . With the exception of some ectothermic species like the leatherback sea turtle and crocodiles , no tetrapods weighing more than 25 kg survived . It marked the end of the Cretaceous period and with it , the entire Mesozoic Era , opening the Cenozoic Era that continues today .   In the geologic record , the K -- Pg event is marked by a thin layer of sediment called the K -- Pg boundary , which can be found throughout the world in marine and terrestrial rocks . The boundary clay shows high levels of the metal iridium , which is rare in the Earth 's crust but abundant in asteroids .   As originally proposed in 1980 by a team of scientists led by Luis Alvarez , it is now generally thought that the K -- Pg extinction was caused by a massive comet or asteroid impact , estimated to be 10 km wide , 66 million years ago and its catastrophic effects on the global environment , including a lingering impact winter that made it impossible for plants and plankton to carry out photosynthesis . The impact hypothesis , also known as the Alvarez hypothesis , was bolstered by the discovery of the 180 km Chicxulub crater in the Gulf of Mexico in the early 1990s , which provided conclusive evidence that the K -- Pg boundary clay represented debris from an asteroid impact . The fact that the extinctions occurred at the same time as the impact provides strong situational evidence that the K -- Pg extinction was caused by the asteroid . It was possibly accelerated by the creation of the Deccan Traps . However , some scientists maintain the extinction was caused or exacerbated by other factors , such as volcanic eruptions , climate change , or sea level change , separately or together .   A wide range of species perished in the K -- Pg extinction . The best-known victims are the non-avian dinosaurs . However , the extinction also destroyed a plethora of other terrestrial organisms , including certain mammals , pterosaurs , birds , lizards , insects , and plants . In the oceans , the K -- Pg extinction killed off plesiosaurs and the giant marine lizards ( Mosasauridae ) and devastated fish , sharks , mollusks ( especially ammonites , which became extinct ) and many species of plankton . It is estimated that 75 % or more of all species on Earth vanished . Yet the devastation caused by the extinction also provided evolutionary opportunities . In the wake of the extinction , many groups underwent remarkable adaptive radiations -- a sudden and prolific divergence into new forms and species within the disrupted and emptied ecological niches resulting from the event . Mammals in particular diversified in the Paleogene , producing new forms such as horses , whales , bats , and primates . Birds , fish and perhaps lizards also radiated .

Global warming controversy <=SEP=> The global warming controversy concerns the public debate over whether global warming is occurring , how much has occurred in modern times , what has caused it , what its effects will be , whether any action should be taken to curb it , and if so what that action should be . In the scientific literature , there is a strong consensus that global surface temperatures have increased in recent decades and that the trend is caused by human-induced emissions of greenhouse gases . No scientific body of national or international standing disagrees with this view , though a few organizations with members in extractive industries hold non-committal positions . Disputes over the key scientific facts of global warming are more prevalent in the media than in the scientific literature , where such issues are treated as resolved , and such disputes are more prevalent in the United States than globally .   Political and popular debate concerning the existence and cause of climate change includes the reasons for the increase seen in the instrumental temperature record , whether the warming trend exceeds normal climatic variations , and whether human activities have contributed significantly to it . Scientists have resolved these questions decisively in favour of the view that the current warming trend exists and is ongoing , that human activity is the cause , and that it is without precedent in at least 2000 years . Public disputes that also reflect scientific debate include estimates of how responsive the climate system might be to any given level of greenhouse gases ( climate sensitivity ) , how global climate change will play out at local and regional scales , and what the consequences of global warming will be .   Global warming remains an issue of widespread political debate , often split along party political lines , especially in the United States . Many of the issues that are settled within the scientific community , such as human responsibility for global warming , remain the subject of politically or economically motivated attempts to downplay , dismiss or deny them -- an ideological phenomenon categorised by academics and scientists as climate change denial . The sources of funding for those involved with climate science -- both supporting and opposing mainstream scientific positions -- have been questioned by both sides . There are debates about the best policy responses to the science , their cost-effectiveness and their urgency . Climate scientists , especially in the United States , have reported official and oil-industry pressure to censor or suppress their work and hide scientific data , with directives not to discuss the subject in public communications . Legal cases regarding global warming , its effects , and measures to reduce it have reached American courts . The fossil fuels lobby has been identified as overtly or covertly supporting efforts to undermine or discredit the scientific consensus on global warming .