My favorite defense to strong 1♣ is Psycho Suction. I filled in 2NT and the 1-level as per the useful space principle. This defense is so flexible that it also applies to small 1♣, strong 1♦, and over the forced responder, e.g. (1♣)-(1♦).

X	Takeout double or stolen bid
1x	Natural or lead-directing
1NT	Non-touching pairs (♠ ♦ or ♥ ♣)
2♣	Clubs or red suits
2♦	Diamonds or majors
2♥	Hearts or black suits
2♠	Spades or minors (supplement to 2NT)
2NT	Minors

Psycho Suction is an extension to the natural defense. It is a superset of the weak twos. The two suiters increase the probabilities of the 2-bids and unanchor them. Psycho Suction establishes a pass-or-correct system where the 2x overcalls are also pass-or-correct. The word “psycho” reflects the risk of playing an undoubled misfit like psychic bids.

Paradox advances

The paradox principle in a pass-or-correct system is to bypass underbids. For example, hearing (1♣)-2♦, we hold

♠ J98
♥ KJ1032
♦ Q98
♣ Q2

Option	Advance
Diamonds	3♦
Majors	4♥

Bid 3♦. Besides diamond support, this bid also shows that we can also raise either major. Underbidding 2♥ conveys too little information and takes away too little space.

The paradox lies in that we do not bid our favorite strain. We have to make the cheapest call of the conjectured advances. Resultantly, we usually bid for the worst case.

Comparison with defenses to 1NT

Similarities

The most common subtype of strong 1♣ is a strong notrump. The opener is so strong that we are unlikely to have a game, so our main goal is to compete with partscores. Our cuebid strain is notrump because opponents have shown strength but no suit.

A common way to devise a defense to 1♣ is using our defense to 1NT. Suction is originally a defense to 1NT. Such a defense to 1NT with no anchor suit is banned in the ACBL Basic+ chart.¹ However, artificial defenses to an artifical opening are generally allowed.² Therefore, we can derive a defense to 1♣ from such an exotic defense to 1NT.

Differences

An obvious difference is that we can access 1-level overcalls. Beware of the lowest 2 overcalls as they give out bidding space.

X	Gives 2 steps (P, XX)
1♦	Gives 1 step (P)
1♥	Neither gives nor takes
1♠	Takes 1 step
1NT	Takes 2 steps

X and 1♦ are better constructive to make bidding space useful to everyone. Natural 1♥ and 1♠ are fine. Try to increase the probability of 2-level overcalls, which take considerable space.

Another difference is that 1NT is limited and descriptive. The opener does not have much to say even if given a second chance to bid. The probability that the opener has a major is also lower. These reasons make major-oriented overcalls effective, e.g. Multi-Landy.

On the other hand, a strong artificial opening is usually unlimited. Forcing overcalls are less effective since they let the opener pass at ease. Thus, a natural defense to 1♣ is stronger than to 1NT. Besides, Inverted Psycho Suction may work for 1NT, but Psycho Suction works better for 1♣.

Discussions

5=4 two suiters

I include some 5=4 two suiters to increase the probabilities of Psycho Suction bids. The rest can be easily expressed with a simple major overcall, where the 4-card suit is lower than the 5-card major.

1♥	5+ hearts
1♠	5+ spades
1NT	4+ spades 5+ diamonds or 4+ hearts 5+ clubs
2♣	6+ clubs or 4+ hearts 5+ diamonds
2♦	6+ diamonds or 4+ spades 5+ hearts
2♥	6+ hearts or 4+ spades 5+ clubs
2♠	6+ spades or 4+ diamonds 5+ clubs
2NT	5+ diamonds 4+ clubs

I believe 5=4 is the sweet spot of two suiters. The original 5-5 is too infrequent to make these overcalls different from weak twos. The 5-4 pattern is as frequent as the single-suited, putting the pass at higher risk. Moreover, 5-4 bids are better guided with an extra step showing equal preference. For example, Landy shows 5-4 in majors, and the 2♦ advance indicates equal preference. Nevertheless, this additional step bears a suit we deny, so it lets opponents come in cheaply.

Strength of X and 1♦

The strength to double is opening values. The double is a two-way call that is either a takeout double or a stolen opening bid with 5+ cards.

The 1♦ overcall is slightly stronger than 1♥ and 1♠ because it gives space yet exhibits no major. I suggest near average strength, i.e. 10+ total points in which there are 8+ HCP. I even recommend this approach to natural 1♣ since 1♦ leaks information without taking space.

Overcalls with 16+ HCP

Congratulations on holding yet another strong club! A comeback after passing the first round definitely reveals 16+ HCP. There are also situations where an initial double is better. To decide the best overcall, we have to investigate their pros and cons.

The pass is better when coming back is easy. The following qualities suggest a pass.

• Single suiter
• 5-card major
• Balanced

The takeout double is made for three suiters. It lets our partner decide the strain. If our partner bids our shortness, we can bid 1NT to provide choices again.

Two suiters fall between these scenarios. First, try to bid 1NT and 2NT since they are forcing. Next, hide a 4-card minor with a pass because introducing the longest suit is often enough. Then, we are left with the following two suiters to double.

• Majors
• 4=5 or more in same-colored suits

When a fit is not found yet, we can easily run to the cheaper suit. This strategy happens to spare 2♣, our rebid to show a regular opener with clubs.

Advance	Majors	Black	Red
1♦	1♥	1♠
1♥		1♠
1♠			2♦

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